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LIFIIVERSIDAD
METRDWLITANñ
MITONOMA
TRABAJO
I
DE
MEDICINA
-
IZTAPALAPA
IV
PRQFECOR:
ALFONSO MARTINEZ.
-
,
INTEGRANTES:
P
f
I
L
JIMENEZ
MORALE5
JESUS.
JIMENEZ
MORALES
MA.
SILVA
CEDILLQ
MIA.
TERESA.
DE LOURDEC.
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r.
!
I
1
*-=
-_
F-
APENDI CE.
L
c
.................... 1
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d e l hipotalamo.
Lk
d e l a t e a p r e o p t i c a ......................
3
MARCO T
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D e f i n i c i o n e s d e temperatura.
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REGLJLACION DE LA TENPERATUHA CORPORAL.........
Funcioh
DETECCION TERMOCTATICA DE
EXCESIVA-papel
‘TENPERATUHA
CORPORAL,
D e t e c c : i o h t e r m o s t a t i c a d e l f r i b - p a p e l de los
r e c e p t , o r e s d e l a p i e l y m e d u l a osea.
I n t e g r a c i o h f i n a l d e ambas s e n a l e s t e r m o s t a t i c a s
d e c a l o r y f r i d en e l h i p o t a l a m o .
MECANISMOS DE AUMENTO DE LA PERDIDA DE CALOR CUANDO
EL. CCIERPD SUFRE SORRECALENTAMIENTD......................4
M e c a n i s m o s p a r a l a c o n s e r v a c i o h y a u m e n t o d e la
p r o d i i c c i o h de c a l o r c u a n d o el c u e r p o se e n f r i a .
REFL-EJOS C
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5
EXPOSICION DEL CUERPO A FRIOC I
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MRRCO MEDICO FISDIOLKOGICO...
MARCO F
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Marcc; m e d i c o y b i o l a g i c o :
T r a t a m i en to.
7
y RehabilitacioA y
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HIPERTERMIG FEBRIL. O NO FEERIL
Un a r g u m e n t o e s p e c i a l e n h i p e r t e r m i a
y t e r a p i a d e cancer-.
HIPERTERMIA PARA LA INGENIERIA: UN CORTO
CDMPRENDID BIOLOGICO.
PRINCIF‘IOS DE MEDICINA FISICA...........................19
EFECTOS FICIDLOGICOC DEL CALOR Y EFECTOS
CLINICDS DE EL CALOR.......
FICHA DE M1:STORIA CLINICFI..
...................................
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14
15
2ü
.22
R e h a b i l i t a c i o h d e p a c i e n t e s con enfermedades
vascular p e r i f e r i c a
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ANALISIS DE TUMORES INTRACRF+NEALES......................25
MRRCO INREFIIERIL...
REFERENCIC
R
REFERENCIR
I?
REFERENCIA
C “........................................59
REFERENCiG
r?
REFERENCIA
El
REFERENCIA
E2
REFERENCIA
F
REFERENCIA
G
REFERENCIA
H “........................................82
REFERENCIR
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REFERENCIA
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7
REFERENCIA
1:
REFERENCIA
1REFERENCIA
1’1
REFERENCIA
N
RIPL~TORRAFñA.
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2i3
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-69
72
Tí3
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74
98
.IO0
1ü3
MCIRCO TEORICO.
TEMPERfiTURE;Es el g r a d o d e i n t e n s i d a d d e Lin c u e r p o , e s p e c i a l m e n t e
c u a n d o se m i d e p o r l a e s c a l a d e un
termometro,la
temperatura
normal
es d e 98.6F (3712) con v a r i a c i o n e s o c a c i o n a l e s d u r a n t e el
d i a , l l e g a n d o a n o mas d e un g r a d o .
La t e m p e r a t u r a es un p o c o mas
a l t a h a c i a l a n o c h e , c u a n d o l l e g a a ser d e 99.1F (37.3C),y e n l a
mafiana p u e d e c a e r h a s t a 97.3F ( 3 6 . 3 C )
El
c u e r p o m a n t i e n e un
e q u i l i b r i o entre l a p r o d u c c i d n y
la
p e r d i d a d e calor,
que el c u e r p o e x p e l e o p r o d u c e c a l o r s e g ü n
el
caso.
E l c a l o r es p e r d i d o m a y o r m e n t e a t r a v e z d e l a p e r s p i r a c i 6 n
y a t r a v e z d e l a i r e y v a p o r i e x p e l i d o d e los p u l m o n e s . E l c a l o r es
producido por
a c c i b n q u i m l c a d e 105 m u s c u l o s y
l a s glandulas
e s p e c i a l m e n t e e n el h i g a d o , el t e m b l o r es una a c c i o n i n v o l u n t a r i a
que p r o d u c e c a l o r .
La s e n s a c i d n
d e c a l o r y f i - i o n o es d e b i d o a un
cambio en
la
temperatura corporal
sino
un c a m b i o e n l a t e m p e r a t u r a d e la
piel.
Cuando l a p i e l se s i e n t e f r i a o c a l i e n t e ,
un m e n s a j e es
enviado al
c e r e b r o que a l b e r g a el m e c a n i s m o que controla l a
t e m p e r a t u r a es p u e s t o e n f u n c i o n a m i e n t o c o n una c o r r e s p o n d i e n t e
caida o e l e v a c i b n d e temperatura.
L a t e m p e r a t u r a d e una p e r s o n a e n f e r m a ,
con f i e b r e puede llegar
h a s t a i 0 4 f F ( 4 0 $ C ) , e n c a s o s severos t a l e s como el momento como l a
muerte
iCV-109LF
í42-43fC) , l a
muerte por
insolacibn
son
t e m p e r a t u r a s m a y o r e s a 11OF í43.3LC).
Una t e m p e r a t u r a menor d e 96$F 'í35.5$C) , p r o d u c e un c o l a p s o .
En
algi.inas e n f e r m e d a d e s y p r o c e d i m i e n t o s o p e r a t o r i o s l a t e m p e r a t u r a
corporal
puede e s t a r considerablemente p o r
d e b a j o d e esta
c i f r a , p o r p l e r i o d o s mas o menos l a r g o s .
E l e n f r i a m i e n t . 0 d e l c u e r p o es g e n e r a l m e n t e d a h i n o p a r a l a s a l u d y
es mas s e r i a p a r a una p e r s o n a c o n una i n f e c c i b n c r o n i c a d e l a
n a r i z y d e l a g a r g a n t a q u e p a r a una p e r s o n a s a n a .
La t e m p e r a , t r r r a e n el i n t e r i o r - d e l " nuc1eo"-- d e l . organismo es
notab1ement.e c o n s t a n t e ,
c a m b i a n d o e n menos d e 0 . 5 t C
d i a tras
d i a , s a l v o e n caso d e e n f e r m e d a d f e b r i l .
De h e c h o ,
un
individuo
d e s n u d o p u e d e qi.iedar e x p u e s t o a t e m p e r a t u r a s b a j a s ,
d e l orden de
iZ$C,o
r e l a t i v a m e n t e a l t a s p o r e j e m p l o 60YC,
c o n s e r v a n d o sin
e m b a r g o , una t e m p e r a t u r a c a s i c o n s t a n t e .
.
Temperatura" d e l n u c l e o " y temperatura d e l a s u p e r f i c i e .
C u a n d o se h a b l a de t e m p e r a t u r a c o r p o r t a l ,
suele entenderse
t e m p e r a t u r a d e l i n t e r i o r , denominada l a t e m p e r a t u r a d e l n u c l e o , y
n o l a t e m p e r a t u r a d e l a p i e l o de t e j i d o s s i t u a d o s i n m e d i a t a m e n t e
d e b a j o d e l a misma,
l a t e m p e r a t u r a i n t e r n a se h a l l a r e g u l a d a e n
f o r m a muy p r e c i s a ;
n o r m a l m e n t e su v a l o r m e d i o n o v a r i a mas d e
O.S$C.
Por o t r a p a r t e l a t e m p e r a t u r a s u p e r f i c i a l s u b e y b a j a
segun l a d e l medio.
Al
hablar
d e r e g u l a c i b n t e r m i c a d e l c u e r p o casi
s i e m p r e nos
referimos a l a t e m p e r a t u r a d e l n c i c l e o a l t r a t a r d e l a c a p a c i d a d
d e l a p i e l p a r a p e r d e r c a l o r h a c i a el m e d i o solemos e n t e n d e r
la
temperatura d e l a s u p e r f i c i e ,
cuando deseamos c a l c u l a r
la
cantidad
d e c a l o r a l m a c e n a d a e n el
cuerpo utilizamos
la
t e m p e r a t u r a c o r p o r a l media.
La t.emperatura c o r p o r a l media p u e d e
1
v a l o r a r s e aproximadamente 1a s i q u i e n t e formula:
Temperatura
media = Temperatura
interna +
s u p e r f i c i a l . í Ver r e f e r e n c i a F.)
0.3
Temperatura
Temperatura c o r p o r a l normal.
hay una t e m p e r a t u r a determinada que pueda c o n s i d e r a r s e
norma1,las mediciones en d i v e r s a s personas normales han mostrado
una amp1 itud.
No
rL
r
L
c
t
c
f
i
c
L
r
i
i
Relaciones
e n t r e l a temperatura corporal
y el
calor
del
cuerpo;calor e s p e c i f i c o de 105 t e j i d o s .
cada
En promedio l a temperatura c o r p o r a l aumenta un grado por
0.83 c a l o r i a s p o r Kg,de peso c o r p o r a l . En o t r a s p a l a b r a s e l Calor
e s p e c i f i c o de l o s t e j i d o s es de O.B3Cal/Kg/gradosC.
C o n t r o l de l a conduccion de c a l o r h a c i a l a p i e l .
La conduccibn de c a l o r p o r l a sangre h a c i a l a p i e l depende de e l
grado de v a s o c o n s t r i c c i d n de l a s a r t e r i o l a s y de l a s anastombsis
a r t e r i o v e n o s a s que mandan sangre a l p l e x o venoso de l a p i e l ; e s t a
es c o n t r o l a d a c a s i t o t a l m e n t e p o r e l sistema
vasoconstriccion
n e r v i o s o simpatico.
De o r d i n a r i o ,
e l s i m p a t i c o mantiene una
actividad tonica,
provocando un c i e r t o grado de c o n s t r i c c i o n
s o s t e n i d o de l a s a r t e r i o l a s de l a p i e l .
Cuando son e s t i m u l a d o s
105 c e n t r o s s i m p a t i c o s d e l h i p o t a l a m o p o s t e r i o r ,
se produce una
c o n s t r i c c i d n de l o s vasos sanguineos mayor t o d a v i a y e l paso se
l a sangre h a c i a l a p i e l cesa c a s i
totalmente;
cuando e s t o s
c e n t r o s p o s t e r i o r e s d e l h i p o t a l a m o son i n h i b i d o s ,
disminuye un
numero de i m p u l s o s s i m p a t i c o s t r a n s m i t i d o s a l a p e r i f e r i a y
los
vasos sanguineos se d i l a t a n . ( v e r r e f e r e n c i a DI.
REOU~CION DE La TENFERATURCI CORPDRAL~FUNCION
DEL HIWTCILCIMO.
La t e m p e r a t u r a d e l organismo e5 r e g u l a d a c a s i
enteramente por
mecanismos
de
r - e t r o a l i m e n t a c i d n n e r v i o s o s en
los
cuales
i n t e r v i e n e c a s i siempre un c e n t r o de r e g u l a c i b n de l a temperatura
situado
en e l hipotalamo.
S i n embargo p a r a que e s t o s mecanismos
debe e x i s t i r
de r e t r o a l imentaci dn f u n c i o n e n s a t is f a c t o r i amente,
tambien un sistema de i d e n t i f i c a c i d n de l a temperatura p a r a
establecer
s i l a t e m p e r a t u r a c o r p o r a l es demasiado a l t a o b a j a .
Algunos de e s t o s r e c e p t o r e s son l o s s i g u i e n t e s :
Receptores de temperatura.
Probablemente l o s r e c e p t o r e s de temperatura m a s i m p o r t a n t e s p a r a
l a r e g u l a c i b n de l a t e m p e r a t u r a c o r p o r a l sean muchas neuronas
s e n c i b l e s a l c a l o r s i t u a d a s en l a r e g i d n p r e d p t i c a d e l h i p o t a l a m o
anterior.
E s t a s neuronas aumentan su f r e c u e n c i a de descarga
cuando l a t e m p e r a t u r a sube,
y l a reducen criando l a temperatura
baja.
La f r e c u e n c i a de descarga puede aumentar 10 veces por
una
elevation de t e m p e r a t u r a de 10 C.
Ademas de e s t a s neuronas s e n c i b l e s
al
calor
en l a r e g i o n
predptica,
e x i s t e n o t r o s r e c e p t o r e s de temperatura:
1 ) Algunas
neuronas s e n s i b l e s a l f r i o en d i s t i n t a s p a r t e s d e l
hipotalamo,
5eptLw-1 y s u s t a n c i a r e t i c u l a r
del
mesencefalo;
aumentan su
f r e c u e n c i a de descarga p o r e x p o s i c i b n a l f r i o (hay pocas neuronas
de e s t e t i p o ;
no se sabe s i i n t e r v i e n e n en l a r e g u l a c i b n de l a
temperatura c o r p o r a l
en c o n d i c i o n e s normales);
2)
Receptores
ccitsneos
de temperatura
i n c l u y e n d o r e c e p t o r e s al
frio
y
receptores a l
calor;
mandan impulsos n e r v i o s o s a l a medula
espinal,
y
luego a l a r e g i b n hipotalamica d e l
cerebro,
para
c o n t r i b u i r a l a r e q u l a c i b n de l a temperatura c o r p o r a l , 3 ) E x i s t e n
r e c e p t o r e s de temperatura
en
l a médula e s p i n a l ,
abdomen y
posiblemente en algunos brganos i n t e r n o s ,
que mandarian Senales
a l s i s t e m a n e r v i o s o c e n t r a l con e l mismo o b j e t o .
DETECCIDN
mm-maTuRcI
TERMOBTATICA
EN
EXCESO)
DE LA TEMPERATURA
-PAPEL DFEL AREA
CORPORAL
PREOPTICA
EXCESIVA
DEL
HIPM6LARO.
En l o s rSltimos ahos,
5e han l l e v a d o a
cavo experimentos que
c o n s i s t i e r o n en c a l e n t a r o e n f r i a r - zonas pequehas d e l
encbfalo,
empleando l o que se ha Hamado un térmodo.
Se t r a t a de un
d i s p o s i t i v o que puede c a l e n t a r s e p o r
medios e l é c t r i c o s ,
o
haciendo pasar a su t r a v e s ayua c a l i e n t e . La p r i n c i p a l r e g i o n d e l
e n c e f a l o en donde e l c a l o r di31 termodo m o d i f i c a l a r e g u l a c i b n de
l a t e m p e r a t u r a es l a r e g i b n p r e á p t i c a d e l h i p o t a l a m o y en menor
A e s t e n i v e l hay
grado en zonas v e c i n a s d e l h i p o t a l a m o a n t e r i o r .
v a r i a s neuronas s e n s i b l e s ,al c a l o r cuya i n t e n s i d a d de descarga
aumenta considerablemente cu,nndo se c a l i e n t a n ;
se c r e e que e s t a s
papel
d e c i s i v o en e l
control
de l a
neuronas desempehan u n
temperatura, c o r p o r a l .
DETECCIDN ERMOSTATICA
DEL FRIO -PAPEL DE RECEPTDRES DE PIEL
MEDULA ESPINAL.
Una de l a 5 formas en l a s c u a l e s e l cuerpo descubre e l f r i o es a l
disminuir
105
r i t m o s de descarga de l a s neuronas s e n c i b l e s al
calor
que hay en e l area p r e o t i c a .
Pero cuando l a t e m p e r a t u r a
c o r p o r a l i n t e r n a ha b a j a d o ~ m a 5 , p o c a sdecimas de grado p o r d e b a j o
de l a normal,
e s t a s nei.ironas generalmente se vuelven
inactivas,
de manera que y a no puede d e s c u b r i r s e mas que produzcan sehales.
Cuando la t e m p e r a t u r a cae mas t o d a v i a o t r o s r e c e p t o r e s , a p a r t e de
l o s que hay en e l h i p o t a l a m o parecen ser 105 que proporcionan.
sehales p r i n c i p a l e s de f r i o .
E s t o s r-eceptores e s t a n l o c a l i z a d o s
sobre t o d o en medula e s p i n a l y p i e l ,
y sus senales c o n t i t u y e n un
impulso init.ensa p a r a que e l cuerpo conserve c a l o r y p a r a que
aumente mucho l a p r o d u c c i d n d e l
mismo por
el
proceso
de
" e s c a l o f r i o".
INTEQRACION FINAL DE AMBAS SENALEC TERMOSTATICAS DE CALOR Y FRIO
EN EL H I P M A L M -EL "TERm)STAlO HIPOTALAMICO".
Aunque l a mayor p a r t e de s e k a l e s p a r a f r i o nacen en r e c e p t o r e s
periféricos,
son t r a n s m i t i d a s a l h i p o t a l a m o p o s t e r i o r ,
donde se
integra
con l a s s e h a l e s d e l
receptor
del
Brea
preotica,
integrando l a s sekalers eferentes f i n a l e s para c o n t r o l a r
l a
p e r d i d a y l a p r o d u c c i b n de c a l o r .
Por l o t a n t o ,
solemos h a b l a r
del
c e n t r o de c o n t r o l de r e g u l a c i d n de l a t e m p e r a t u r a como el
t e r m o s t a t o h i p o t a l ami co.
L a c u r v a c o n t i n u a muestra que c a s i presisamente en 37$C,empieza
l a sudacion,
que aumenta rapidamente cuando l a temperatura se
e l e v a mas.
Por o t r a p a r t e ,
cesa a c u a l q u i e r
temperatura p o r
debajo de e s t e mismo v a l o r c r i t i c o ( v e r
figuras
1,Z
en l a
r e f e r e n c i a R).
3
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366
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310
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lEh!PERAl!li:A DE LA L A H I M ' a i i d o l C)
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c
...
rmwrsme
DE
ALJNEMTO
SUFRE BOBRECALENTMIENTO.
DE
LA PERDIDA DE CALOR CUANDO
EL
CUERPO
El
s o b r e c a l e n t a m i e n t o d e l a r e a t e r m o s t a t i c a p r e o p t i c a aumenta l a
p e r d i d a de c a l o r de dos maneras;
1 ) estimulando l a s glandulas
sudoriparas
para perder
icalor
por
evaporacibn,
y 2)
por
i n h i b i c i o n de c e n t r o s s i m p a t i c o s d e l h i p o t a l a m o p o s t e r i o r
que
suprime e l v a s o c o n s t r i c t o r de l o s vasos cutaneos y de e s t a forma
tambien
permite
una v a s o d i l a t a c i o n
mas. i n t e n s a t o d a v i a y
i n h i b i e n d o e l mecanismo d e l e s c a l o f r i o p a r a e v i t a r una p r o d u c i b n
e x c e s i v a de c a l o r .
NECcIFIISMüS PARA CONSEWñCION Y AUMENTO DE PRODUCCION
EL CUERPO SE ENFRIA.
DE
CALOR
CUANM)
i
-
i
-
r
L
Cuando l a zona p r e o p t i c a d e l h i p o t a l a m o se e n f r i a p o r debajo de
e n t r a n en juego mecanismos e s p e c i a l e s p a r a
aproximadamente 37XC,
conservar e l c a l o r e x i s t e n t e en l a economia y o t r o s p a r a aumentar
l a p r o d u c c i b n d e l mismo en l a s i g u i e n t e forma.
Conservacinn de c a l o r . V a s o c o n ~ t r i c c i b nen l a p i e l .
Uno de l o s p r i m e r o s e f e c t o s e s l a i n t e n s a v a s o c o n s t r i c c i b n de 105
vasos cutaneos en t o d a l a economia. E l l o depende de l a l i b e r a c i b n
de l a s zonas s i m p a t i c a s h i p o t a l a m i c a s p o s t e r i o r e s , que se l i b e r a n
i n h i b i c i b n p o r l a s sehales t e r m o s t a t i c a s p r e o p t i c a s y
de la
probablemente
mas t o d a v i a d e l
impulso p r o v e n i e n t e de
106
r e c e p t o r e s d e l f r i o en p i e l y medZila e s p i n a l .
En consecuencia,
l a s areas s i m p a t i c a s aumentan 5u a c t i v i d a d ,
y en t o d o el
cuerpo
5e
p r aduce
int enso
vasoconstr ic c i bn
adrener g i ca.
Esta
v a s o c o n s t r i c c i b n i m p i d e que l a conduccibn de c a l o r de l a s p a r t e s
i n t e r n a s d e l cuerpo a l a p i e l . ( v e r r e f . D).Cupresion d e l sudor.
El
sudor
queda completamente s u p r i m i d o cuando se e n f r i a e l
termostato
prebptico
por
debajo
de
~ i n o s 37YC.
Est0
manifiestamente
interrumpe e l
enfriamiento del
cuerpo
por
lo que se r e f i e r e a l a evaporacibn
evaporacibn,
excepto
insensible.
Flumento d e p r o d u c c i d n de c a l o r .
L.a p r n d u c c i b n de c a l o r aumenta en t r e s formas d i f e r e n t e s cuando
l a t e m p e r a t u r a d e l t e r m o s t a t o h i p o t a l a m i c o cae por debajo de 37C:
i
E s t i mu1 a c i an h i p o t a l amica d e l escal O F r i o .
L o c a l i z a d a en
l a p a r t e dorsomedial
del
hipotalamo p o s t e r i o r ,
c e r c a de l a pared d e l t e r c e r v e n t r i c f i l o , e s t a una zona denominada
c e n t r o motor p r i m a r i o p a r a e s c a l o f r i o .
E s t a area normalmente e s
i n h i b i d a p o r s e h a l e s procedentes d e l a r e a t e r m o s t a t i c a pr-ebpotica
pero estimulada por
s e k a l e s p r o v e n i e n t e s de p i e l
y
medola
espinal.
Por
l o t a n t o en r e s p u e s t a al
f r i o e s t e c e n t r o es
activado y
t r a n s m i t e impulsos s i g u i e n d o haces b i l a t e r a l e s que
b a j a n p o r e l t a l l o c e r e b r a l pasan a l o s cordones l a t e r a l e s de l a
medhla, y f i n a l m e n t e van a l a s motoneuronas a n t e r i o r e s .
El
metAbolismo muscular aumenta l , a p r o d u c c i d n de c a l o r
muchas
veces
elevando l a p r n d u c c i b n t o t a l h a s t a 50% i n c l u s o a n t e s de
i n i c i a r s e 10s e s c a l o f r i o s .
E s t o probablemente r e s u l t e de una
r
4
....
"
r
.
o s c i l a c i h n c o n r e t r o a l i m e n t a c i & n d e l mecanismo d e r e f l e j o d e
e s t i r a m i e n t o de 105 husos musculares.
D u r a n t e e1
escaiofrio
maximo l a p r o d c i c c i & n c o r p o r a l d e c a l o r p u e d e a u m e n t a r h a s t a c i n c o
veces 1a n o r m a l .
-
I
-
L
c
L
c
c
i
c
L
c
r
L
c
E x c i t a c i b n s i m p a t i c a "quimica" d e l a produccidn d e c a l o r .
L.a e x c i t a c i d n s i m p a t i c a ,
o l a adrenalina y
noradrenalina
circulantes,
podian dar
Irigar
a un a u m e n t o i n m e d i a t o d e l
m e t a b o l i s m o c e l u l a r ; este e f e c t o se l l a m a termogLnesis q u i m i c a , y
p a r a c e d e b e r s e en p a r t e c u a n d o menos,
a l a capacidad de l a
noradrenalina
y
adrenalina d e desacoplar
la
fosforilacibn
oxidativa,
con
l o c u a l se h a c e n e c e s a r i o una mayor o x i d a c i b n d e
los e l e m e n t o s p a r a o b t e n e r io5 c o m p u e s t o s d e f o s f a t o d e a l t a
e n b r g i a r e q u e r i d o s p o r l a f u n c i d n normal d e l o r g a n i s m o
El
g r a d o d e t e r m o g h e s i s q u i m i c a q u e t i e n e l u g a r e n un animal es
casi
directamente proporcional a l a cantidad d e grasa parda que
e x i s t e e n su5 t e j i d o s . E s t e e5 Lln t i p o d e g r a s a q u e c o n t i e n e gran
numero d e m i t o c o n d r i a s e n s u s c e l u l a s p r o v i s t a s d e una r i c a
inervacion simpaticd.
Por e s t i m u i a c i b n s i m p a t i c a , el metabolismo
o x i d a t i v o d e l a s m i t o c o n d r i a , s se e s t i m u l a c o n s i d e r a b l e m e n t e , p e r o
esto p r o b a b l e m e n t e t i e n e l u g a r s i n a c o p l a m i e n t o ,
d e manera q u e
5 0 1 ~ 1se f o r m a n p e q u e h a s c a n t i d a d e s d e ñTP.
REFLEJOS CUTCIMOS LOCALES.
Cuando una p e r s o n a p o n e su p i e d e b a j o d e una l a m p a r a c a l i e n t e y
l o d e j a ahi por b r e v e tiempo,
p e r c i b e un c a l e n t a m i e n t o l o c a l
y
l i g e r o s u d o r l o c a l . I n v e r s a m ~ n t e , c u a n d o se c o l o c a un p i e e n a g u a
f r i a h a y v a s o c o n s t r i c c i d n y cesa l a p r o d u c c i b n d e s u d o r .
Estas
r e a c c i o n e s d e p e n d e n d e r e f l e j o s m e d u l a r e s l o c a l e s q u e se p r o d u c e n
a p a r t i r d e 105 r e c e p t o r e s c u t a n e o s h a s t a l a m e d h l a y d e regreso
hacia
l a misma z o n a c i i t a n e a .
S i n embargo,
su i n t e n s i d a d es
r e g u l a d a p o r el t e r m o s t a t o h i p o t a l a m i c o ,
d e m a n e r a q u e el e f e c t o
global
es a p o r x i m a d a m e n t e p r o p o r c i o n a l a l a s e h a i
termoatatica
m u l t i p l i c a d a p o r l a sePial l o c a l .
E f e c t o s p e r j u d i c i a l e s d e l a temperatura elevada.
C u a n d o l a t . e m p e r a t u r a c o r p o r a l se e l e v a p o r e n c i m a d e 41.5tC suele
empezar
a p r o d u c i r l e s i o n p a r e n q u i m a t o s a d e muchas
celulas.
El
e s t u d i o h i s t b l o g i c o e n una p e r s o n a m u e r t a d e
hiperpirexia
descubre hemorragi a s l o c a l e s y degeneracion parenquimatosa
de
c e l u l a s en toda
l a econornia.
El
cerebro tiene particular
t e n d e n c i a a s u f r i r p o r q u e una v e z d e s t r u i d a s l a s n e u r o n a s n o son
substituidas.
Cuando l a t e m p e r a t u r a c o r p o r a l se e l e v a h a s t a 4345.!WC,
el p a c i e n t e suele t e n e r u n a s p o c a s h o r a s d e v i d a a m e n o s
q u e l a t e m p e r a t u r a se h a g a d e s c e n d e r r a p i d a m e n t e h a s t a v a l o r e s
n o r m a l e s m o j a n d o el
c u e r p o con a l c o h o l q u e se e v a p o r a y
lo
e n f r i a , o sumergiendo10 en agua h e l a d a ( v e r ref. E 1,2).
Efectos
de
medicamentos y p r o d u c t o s
quimicos
sobre
la
t e m p e r a t Lira.
Un numero e x t r a o r d i n a r i a m e n t e d e s u b s t a n c i a s e x t r a h a s i n y e c t a d a s
los l i q u i d o s c o r p o r a l e s p u e d e h a c e r q u e l a t e m p e r a t u r a
en
corporal
se
el eve
O
5ea
que
resulten
pir&genos,bacterias,polenes,pOiVOs y v a c u n a s s o n t o d o s p i r b g e n o s
por su contenido proteinico.
5
EXPOSICION DEL C U E R W A FRIOS INTENSOS.
Una persona expuesta a l agua h e l a d a d u r a n t e unos 20 o 30 m i n .
suele morir
p o r f i b r i l a c i b n o p a r o d e l corazbn a menos que se
t r a t e de inmediato.
Por entonces l a temperatura
i n t e r n a del
cuerpo habra c a i d o h a s t a a l r e d e d o r de 25C.
S i n embargo,
si se
c a l i e n t a rapidamente p o r a p l i c a c i b n de c a l o r
externo,
l a vida
muchas veces puede s a l v a r s e .
El
t r a t a m i e n t o de un p a c i e n t e cuya t e m p e r a t u r a c o r p o r a l a c a i d o
alrededor
de 22 a 26C s u e l e c o n s i s t i r en a p l i c a r c a l o r humedo en
forma
de bako,
o compriesas empapadas en agua
caliente,
S i l a temperatura
del
aproximadamente a temperaturas de 43tC.
agua e s menorl e l cuerpo reclupera c a l o r demasiado lentamente p a r a
si l a t e m p e r a t u r a es mayor
l a piel
lograr
b e n e f i c i o mhimo;
puede l e s i o n a r s e gravemente p o r c a l e n t a m i e n t o e x c e s i v o m i e n t r a s
no dispone de r i e s g o sangui neo adecuado.
MCIRCO
MEDICO FISIOLOC~CO.
Temperatura;
Hay dos t i p o s de organos s e n s i b l e s a l a temperautra.Los
que
responden a l
mawimo a temperaturas l i g e r a m e n t e s u p e r i o r e s a l a
del
cuerpo y 105 de r e s p u e s t a mawima a temperaturas escasamente
i n f e r i o r e s a l a corporal.
L o s p r i m e r o s son 105 organos s e n s i b l e s
llama
p a r a 10s que se l l a m a c a l o r y 105 segundos p a r a l o que se
frio.
S i n embargo,los e s t i m u l o s adecuados son en r e a l i d a d do5
grados d i f e r e n t e s de c a l o r ,
p u e s t o que e l f r i o no r e p r e s e n t a
forma
de e n e r g i a alguna y l a sensacibn de c a l i e n . t e es una
combinacibn de c a l o r y d o l o r l i g e r o .
Aunque
l a presente controversia
acerca de l a
especifidad
h i s t b l o g i c a de l a 5 t e r m i n a c i o n e s cutaneas h a p u e s t o en duda l a
e s t r u c t u r a d e t a l l a d a de 105 organos s e n s i b l e s a l c a l o r y al f r i o .
l..as pequeñas f i b r a s m i e l i n i z a d a s que t r a n s m i t e n l a s e n s i b i l i d a d
t e r m i c a son de 2 a 5 micras,de d i a m e t r o y pertenecen a l grupo Ad
de E a r l a n g e r
y
Gasser
( v e l o c i d a d de conduccibn
12-3üm/sog,
d u r a c i b n de l a e s p i g a 0.4-0.5m/seg,
p e r i o d o r e f r a c t a r i o 0.4lmseg).
L.os
i m p u l s o s que v i a j a n p o r
e l l a s llegan a
l a
circonvolucibn
posrol&ndica a traves del
f a s c i c u l o espinot a l a m i c o l a t e r a l y de la r a d i a c i b n t a l a m i c a .
Debido
CI
que
los
organos . s e n s i t i v o s
estan
situados
subepitelialmente,
e5 l a temperat.ura de l o s t e j i d o s subcutaneos
l a que determina l a 5 respuestas.
Los o b j e t o s m e t a l i c o s f r i b s se
sienten
ma5 f r i b s que l o s o b j e t o s de madera a l a misma
temperatura, p o r que l o s m e t a l e s conducen e l c a l o r de l a p i e l mas
rapidamente, e n f r i a n d o a los t e j i d o s subcutaneos en mayor grado.
Regulacibn de l a temperatura;
En e l organismo e l c a l o r e s p r o d u c i d o p o r e l e j e r c i c i o muscular,
por
l a e s t i m u l a c i b n de l o s a l i m e n t o s y p o r t o d o s l o s procesos
v i t a l e s que c o n t r i b u y e n a l a t a z a m e t a b o l i c a b a s a l .
E l calor
es
p e r d i d o del cuerpo p o r r a d i a c i o n e s , conduccibn y v a p o r i z a c i b n d e l
agua es l a s v i a s r e s p i r a t o r i a s y en l a p i e l .
Pequekas
cantidades
de c a l o r tambien se p i e r d e n en o r i n a y
6
en
l a s h e c e s el b a l a n c e o entre l a produccibn y p e r d i d a d e c a l o r
d e t e r m i n a l a temperatura c o r p o r a l . D e b i d o a que l a v e l o c i d a d d e
l a s r e a c i o n e s q u i m i c a s v a r i a r i con l a t e m p e r a t u r a y a causa d e que
IDS sistemas e n z i m a t i c o s d e l o r g a n i s m o s t i e n e n un margen e s t r e c h o
e n el
cual su f u n c i o n es optima,
l a s f u n c i o n e s normales d e l
c u e r p o dependen d e una t e m p e r a t u r a r e l a t i v a m e n t e c o n s t a n t e .
-Porkilotermos
( a n i m a l e s d e s a n g r e f r i a ) . Los mecanismos d e
a j u s t e s o n r u d i m e n t a r i o s y son los r e p t i l e s , e n l o s a n f i b i o s y e n
l o s peces.
-Homeotermos
(animales d e sangre c a l i e n t e ),
o p e r a un grupo d e
r e s p u e s t a s r e f l e j a s que se i n t e g r a n
e n el h i p o t a l a m o para
mantener
l a t e m p e r a t u r a c o r p o r a l d e n t r o d e un estrecho margen a
p e s a r d e l a s a m p l i a s f l ~ ~ c t u a c i o n edse l a t e m p e r a t u r a ambiente. En
los p a j a r o s y e n 105 mamiferos.
1-05 a n i m a l e s i n v e r n a n t e s son una e,:cepcibn p a r c i a l , p u e s m i e n t r a s
e s t a n d e s p i e r t o s son hemeot&rmicos, p e r o d u r a n t e l a i n v e r n a c i b n
uu t e m p e r a t u r a c o r p a r a l baJa.
Temperatura normal d e l cuerpo.
el hombre,
l a c i f r a t r a d i c i o n a l normal p a r a l a t e p W & W a
oral e5 d e 37SC. con una v a r i a c i b h e s t a n d a r d e 0.21C.
V a r i a s p a r t e s d e l c u e r p o 5e encuentran a d i f e r e n t e s t e m p e r a t u r a s
y
l a magnitud d e l a d i f e r e n c i a d@ trmpmratura entre l a s d i v e r s a s
p a r t e s v a r i a con l a t e m p e r a t u r a ambiente.
Las extremidades estan
g e n e r a l m e n t e mas f r i a s que e l resto d e l cuerpo,
l a temperatura
r e c t a l es r e p r e s e n t a t i v a d e l e j e d e l c u e r p o y v a r i a menos coi;, los
cambios e n l a t e m p e r a t u r a ambiente ( v e r ref.C y H).
La t e m p e r a t u r a d e l q a boca es normalmente 0.32 mas b a j a q u e l a
rectal,
p e r o es a f e c t a d a
por muchos f a c t o r e s , i n c l u y e n d o
la
ingestion d e alimentos frios y c a l i e n t e s ,
l a masticacion
de
c h i c l e , fumar y l a r e s p i r a c i o n bucal.
1.a t.emperatura d e l a p a r t e c e n t r a l d e l
c u e r p o humano normal
e x p e r i m e n t a una f l u c t u a c i b n d i u r n a r e g u l a r
d e O.CJ-O.7WZ.
En
i n d i v i d u o s que duermen d u r a n t e l a noche y e s t a n d e s p i e r t o s e n el
dia,
l a t e m p e r a t u r a es mas b a j a d u r a n t e el
suePlo,
ligeramente
mayor e n e s t a d o d e v i g i l i a t r a n q u i l a y sube con l a a c t i v i d a d .
En
l a mujer
tamhien existe un c i c l o menstrfial d e l a v a r i a c i b n d e
t e m p e r a t u r a c a r a c t e r i z a d o por un cambio d e temperatura b a s a l
en
el
tiempo d e l a o v ~ l a c i & n , l a regulac.ibn d e l a temperatura es
menos p r e c i s a e n los riihos pequekos y normalmente ellos pueden
tener
una t e m p e r a t u r a que es aproximadamente C).5$C mayor que l a
normal e s t a b l e c i d a p a r a 105 a d u l t o s .
Durante el
e j e r c i c i o el c a l o r p r o d u c i d o p o r
l a concentracibn
muscular
se acumula e n el
cuerpo y
l a temperatura r e c t a l
normalmente sube h a s t a 4 0 X .
E s t a e l e v a c i b n es d e b i d a e n p a r t e a
la
i n c a p a c i d a d d e 105 mecanismos d i s i p a d o r e s d e c a l o r p a r a
e n f r e n t a r E\ l a c a n t i d a d grandemente incrementada d e c a l o r que es
p r o d u c i d a , p e r o hay e v i d e n c i a d e que, ademas ocurre una e l e v a c i b n
d e l a t e m p e r a t u r a c o r p o r a l a l a cual 105 mecanismos d i s i p a d o r e s
d e c a l o r son a c t i v a d o s d u r a n t e el e j e r c i c i o .
La t e m p e r a t u r a d e l
c u e r p o tamhien sube l i g e r a m e n t e d u r a n t e l a e x c i t a c i b n emocional,
probablemente d e b i d o a l a t e n s i o n i n c o n s i e n t e d e 105 musculos.
Cronicament:e e s t a e l e v a d a h a s t a 0.5K cuando l a t a z a m e t a b o l i c a es
En
a l t a por e j e m p l o e n e l h i p e r t i r o i d i s m o ,
7
y disminuida por e j e m p l o
en e l mixidema.
FIlgunos a d u l t o s aparentemente normales t i e n e n una t e m p e r a t u r a
cronicamente a r r i b a d e l l i m i t e normal í h i p e r t e r m i a c o n s t i t u c i o n a l
).
P e r d i d a de c a l o r ;
-La
radiacian:
Es l a t r a n s S e r e n c i a de c a l o r de un o b j e t o a o t r o
con e l c u a l no e s t a en c o n t a c t o .
-La
conduccibn:
Es e l
i n t e r c a m b i o de c a l o r
de un o b j e t o a
d i f e r e n t e s t e m p e r a t u r a s que se encuentran en c o n t a c t o e n t r e s i .
-La conveccibn:
O sea e l movimiento de l a s moleculas de un gas o
de un l i q u i d o o de una temperatura a o t r o s i t i o
de diferente
temperatura
ayuda a l a conduccibn,
cuando un i n d i v i d u o se haya
en un ambiente f r i o p i e r d e c a l o r por conduccibn a l a i r e que lo
rodea y p o r r a d i a c i o n a l o s iobjetos v e c i n o s f r i o s (ver r e f . D ) .
MARCO FISIOLOOICO.
'
Temperatura
del
cuerpo 'y su
control:
Los
mecani smos
especialmente mantienen un n i v e l , en muchos mamiferos, aves e t c ,
un e s t a d o c l a r o e n t r e l a p r o d u c c i b n de c a l o r y su p e r d i d a h a c i a
el
medio,
a5i
que e l i m i n a d e l cuerpo y e s t a c e r c a be un n i v e l
normal,
s i n l i m i t e restringido.
Todos 105 organismos producen
calor
m e t a b o l i c o y reaccionlas e x o t & r m i c a s cuando e l cuerpo e s t a
en descanso,
e l corazon,
cerebro,
v i s c e r a s ( y notablemente el
h i g a d o ) ? y l l e g a a 5er de un 50% d e e l t o t a l d e l
calor.
En e l
ejercicio
grandes c a n t i d a d e s de c a l o r
son p r o d u c i d a s
mas
p e r i f e r i c a m e n t e por
105 mu5culos.
La c i r c u l a c i b n d e l
cuerpo
tiende
a i g u a l a r s e l a temperatura s i n un corazbn c e n t r a l ,
dado
105 a c a r r e o s de c a l o r de l a s u p e r f i c i e d e l
cuerpo h a c i a
por
afuera.
El
tamaho de e l cuerpo d e l corazbi; en d i c h a temperatur-a e s m a s o
menos uniforme,
depende de e l estado p a r t i c u l a r de e l s i s t e m a y
su amhient,e,Fig.Al,
muestra dos p o s i b l e s d i s t r i b u c i o n e s de
t e m p e r a t u r a en e l cuerpo.
Comparada con e l cuerpo en un ambiente
caliente,
e5
r e l a t i v a m e n t e pequeho en e l corazbn y es cercano a
l a temperat.ura normal en e x p o s i c i b n f r i a .
La t e m p e r a t u r a de l a p i e l e s mas frecuentemente
e n t r e l a del
cuerpo d e l corazdn y l a temperatura ambiente,
excepto cuando e l
calor
evaporado y son grandes p e r d i d a s .
Siempre un mecanismo de
f u e n t e de vapor,
son a v i a b l e s p a r a mantener l a temperatura d e l
cuerpo d e l corazbn,
e s t o e s p r o t e c c i b n de organos i n t e r n o s ,
o
t r a v e s en l a r g o s cambios de temperatura.
Nosotros d e f i n i m o s e s t r u c t u r a s en l a i n f o r m a c i b n procesada p o r e l
h i p o t a l a m o en l a temperatura l o c a l d e l cerebro, de l a t e r m i n a c i b n
n e r v i o s e n s i t i v a de temperatura en l a p i e l
y
q u i z a s de l a
temperatura
de 105 sensores d e l cuerpo l a c u a l
es d e s i n t e g r a d a
hacia e l
e x t e r i o r d e l cerebro,. y p o r c o n s i g u i e n t e . e l c o n t r o l
externo y todos
l o s mecanismos de c a l o r
en
l a s perdidas.
production
y
preservacibn,
actividad
vasomotora,
rangos
"control
metabolicos,
actividad
sudomotora.
Esto
es el
central",tiene
una f i n a s e n s i b i l i d a d
para desviaciones
de
temperatura, pone puntos.
Nosotros
podemos d i b u j a r un diagrama general de bloques
8
Fig,A2,
i n d i c a n d o l a s p r i n c i p a l e s componentes d e el c o n t r o l , l a p a r t e d e l
control d e #el s i s t e m a t e r m o r e g u l a t o r i o , y s u 5 muchas 'conexiones.
La c o n s t r u c c i d n d e un modelo d e l s i s t e m a d e r e t r o a l i m e n t a c i b n
es
un termost,ato, que f u e p r o v i s t o p a r a ser usado,
especialmente
para d e t a l l a r
l a a c c i b n d e el c o n t r o l y m o d i f i c a c i b n d e poner
puntos, es una f i e b r e . Ademar; d e v e r l a r e l a c i b n entre el sistema
c o n t r o l y l a r e g u l a c i b n d e l a t e m p e r a t u r a y los l a t i d o s c a r d i a c o s
(ver R e f . 1 ) .
El
sistema d e c o n t r o l ;
E l c a l o r es p r o d u c i d o a t r a v e s d e l
c u e r p o por un p r o c e s o m e t a b o l i c o , esto induce estremecimiento por
un
camino
d e el
sistema neuromuscular p r o d u c i e n d o
calor
usualmente de p r o t e c c i b n ,
c o n t r a el
frio,
a t r a v e s d e el
incremento e n l a c i r c u l a c i b n ,
da e s c a l o f r i o e n 105 m u s c u i o s p a r a
traer
mas s a n g r e e n
la
periferia,
particularmente
para
c o n t r a r e s t a r el i n c r e m e n t o d e calor p r o d u c i d o a t r a v e s d e g r a n d e s
cantidades
de calor perdido.
L a s c o n t r a c c i o n e s r i t m i c a s d e el
corazon a s i
como el recur!so d e c a l o r , e n e r g i a
disipada en
la
circulacidn,
d e b i d o a l a v i ! i c o c i a d d e l a s a n g r e a p a r e c e como una
pequeha
cantidad
d e calor.
En e j e r c i c i o s v i g o r o s o s el c a l o r
producido por
el
c u e r p o p u e d e ser d e 10-2Omin.
el
basic0
r e s t r i n g i m i e n t o d e el n i v e l .
A s i que el c u e r p o r e q u i e r e un muy
E l i n c r e m e n t o d e a c t i v i d a d e s e n el sistema
e f i c i e n t e termostato.
nervioso
adrenergico
autonomo
puede
ser
bajo
control
el r a n g o m e t , a b o l i t o a t r a v e s d e l
cuerpo.
Estos
centra1,dirige
c o n s t i t u y e n u n r e c ~ t r s oa d i c i o n a l d e c a l o r p o s i b l e l l a m a d o p a r a
v e r s e en medios f r i o s .
Los e f e c t o s a l a r g o p l a z o pueden
tambien
i n c l u i r un
incremento e n l a s e c r e s i d n de t i r o x i n a por glandula
t i r o i d e a , que e n turno e s t i m u l a el r a n g o m e t a b o l i c o í d e s p u e s d e un
retraso d e s e v e r o s d i a s ) .
Este mecanismo,
es i m p o r t a n t e en l a
a d a p t a c i d n a irn c l i m a f r i o ya q u e hay un i n t e r c a m b i o entre l a 5
vena5 y a r t e r i a s d e el s i s t e m a c i r c u l a t o r i o , se c i e r r a uno o otro
y esto puede ser b e n e f i c i o s o e n e x p o s i c i o n e s a l f r i o ,
siendo l a s
a r t e r i a s s a n g u i n e a s r e f r e s c a d a s por un c o n t o r n o o retorno v e n o s o
enfriador (ver Ref. J).
S e n s o r e s d e temperatura:Control c e n t r a l homeotermico y modos d e
control
de
temperatura;
En l a s e c c i b n a n t e r i o r
nosotros
ennumeramos los e f e c t o s que a t r a v e s d e un c i r c u i t o r e f l e j o
a u t o m a t i c 0 d e el
sistema d e l
t e r m o s t a t o pueda a c t u a r p a r a
m a n t e n e r un r a n g o d e t e m p e r a t u r a e n el c u e r p o s i n un r a n g o optimo
f i si o1 o g i camen te.
L.a c o n s t r i cc i bn a r ter i a l cutanea o d i 1a t a c i bn,
el
metabolismo es c o n t r o l a d o p a r a aumentar o d i s m i n u i r ,
y
los
muscul OS
pueden
setexcitados
ritmicamente
para
dar
e s c a l o f r i o ( q u e es tambien un control v o l u n t a r i o p a r t i c u l a r m e n t e ) .
Ademas g l andul as e s p e c i a l es pueden ser esti mu1 adas p a r a s e c r e t a r
sudor,
asi
que l a s g r a n d e s c a n t i d a d e s d e c a l o r
e v a p o r a d o son
dadas por el c u e r p o cuando hay p e r d i d a d e c a l o r por c o n v i c c i b n y
r a d i a c i b n son l i m i t a d a s . E l c o n t r o l d e esos e f e c t o s depende d e l a
integracidn
de
mas D m e n o s a r e a s b i e n
definidas en
el
h i p o t a l amo ( q u e
tiene f uncciones a d i c i o n a l e s importantes e n l a
r e g u l a c i o n d e el b a l a n c e e l e c t r o l i t i c o , v o l d m e n
sanguineo,presibn
sanguinea,et.c.)
Hay e v i d e n c i a p a r t i c u l a r m e n t e c o n t r a d i c t o r i a y
ademas c o n t e s t a l o a n t e r i o r que el h i p o t a l a m o es el
centro de
p r o t e c c i b n c o n t r a el c a l o r t o t a l ,
hipotalamo p o s t e r i o r e l i g e l a
defensa
c o n t r a el e n f r i a m i e n t o y 105 e s t a d o s d e e s t a s d o s a r e a s
.
9
T
I
a
t i e n e i n f l u e n c i a i n h i h i t o r i a s en cada una.
El
modelo p a r t i c u l a r de t e r m o - c o n t r o l e l e g i d o p a r a a c t i v i d a d e s
sin
dependencia d e l
h i p o t a l a m o dependen en
forma
local,
temperatura
h i p o t a l a m i c a y de i n f o r m a c i ó n a f e r e n t e n e u r a l de e l
l a
c o n j u n t o de n e r v i o s s e n s i t i v i ~ sp e r i f e r i c o s de l a temperatura,
temperatura
local de el c e n t r o t e r m o - - c o n t r o l es determinado por
l a s a r t e r i a s sanguineac por el f l u i d o sanguine0 c e r e b r a l ,
p o r el
rango m e t a b o l i c 0 l o c a l ,
y p o r su b a j a c o n d u c t i v i d a d c a l o r i f i c a
p a r a SLI e n t r a d a en o t r a s p a r t e s d e l cer-ebroíver r e f ,medicas).
HIPERTERNIA:
r
,
i
c
r
i
r
L
r
i
c
L
c
Es c u a l q u i e r
aumento de
l a temperatura
i n t e r n a del, cuerpo
provocado p o r e l desequi 1i b i - i o de los procesos termoreguladores
organicos, t a n t o p o r l a p r o d u c c i d n exagerada de c a l o r como p o r l a
eliminacibn
insuficiente
del
mismo;generalmente
estos
dos
factores
se
suman.
Las causas de
la
hipertermia
son
d i v e r s a s ; enf ermedades
infecciosas (se
habla
entonces
de
f i e b r e ) ,causas
f i s i c a s i g o l p e de s o i , g o l p e
de calor-,etc),causas
t o d a s u b s t a n c i a que
to:: ic a s ( e s t r ic n i na, t ebai na, e t c en g e n e r a l
e x c i t e e l s i s t e m a n e r v i o s o produce h i p e r t e r m i a ) .
,
HI POTERMIA
:
Es e l descenso de l a t e m p e r a t u r a c o r p o r a l p o r debajo de 1 0 5 36C
de l a e s c a l a termometrica.
Se p r e e s n t a en l o s r e c i e n nacidos, en
l o s p e r i o d o s de h i p o n u t r i c i b n p r o l o n g a d a ( i n a n i c i b n ) ,
despues de
hemorragias p r o f u s a s ,
de 'traumas sobre e l c e r e b r o y sobre el
abdomen,de
i n t e r v e n c i o n e s q u i r ? ~ r g i c a s , en algunas enfermedades
algunos
inf e c c i osas ( c o l era, d i s e n t e r i a ) en
en venami en t os (por
quinina,
morfina,etc.).
P e r u l a forma mas grave de h i p o t e r m i a 5e
p r e e s n t a en e l " A l t e r i s m o " ,
d e b i d o a l a e x p o s i c i o n prolongada de
frio.
E x i s t a tambien
l a h i p o t e r m i a provocada denominada i n v e r n a c i b n
a r t i f i c i a 1 , q u e c o n s i s t e en el e n f r i a m i e n t o g e n e r a l d e l
organismo
de
enfermos que deben someterse o c i e r t a s
intervenciones
g e n e r a l i z a d o que
q u i r u g i c a s graves: e s t e enf v i amiento c o r p o r a l
l l e v a c o n s i g o l a d i s m i n u c i b n n o t a b l e d e l metabolismo b a s a l de l o s
t . e j i d o s y p o r l o t a n t o provoca una a c t i v i d a d v i t a l r e d u c i d a que
permite a l
p a c i e n t e sopor,tar l a i n t e r v e n c i b n s i n r e c u r r i r
al
empleo de s u s t a n c i a s a n e s t e s i c a s
,
H M C O MEDICO Y BIOLWICO: Y REHAEILITACION Y TRATMIENTüSl
c
Tumbr;
L i t e r a l m e n t e un nud'o o hinchazon,aunque el t e r m i n o usado
p a r a d e s c r i b i r l a hinchazon de t e j i d o s normales como o c u r r e n en
una i n f l a c i b n o edema d e l agrandamiento de organos t a l e s como el
hazo,higado
o rinones.
Un tumar es una masa de c e l u l a s que
recuerdan
al
tejido
ordinario
y
que
se
desarro11a
independientemente como c r e c i m i e n t o nuevo,
s i r v i e n d o a ninguna
funcibn u t i 1 (ver ref.D).
Cuando un t e j i d o se forma en i o 5 vasos sanguineos e5 llamado
angibma.
Cuando t a l
t e j i d o se forma en l o s t e j i d o s g r a s o s es llamado
1 ipoma.
Cuando t a l t e j i d o se forma en 105 c a r t i l a g o s es llamado condrdma.
Algunas
veces aparecen tumoi-es compuestos de t e j i d o s q u e no son
p a r e c i d o s a l d e los o r g a n o s que los a l b e r g a n , a l g u n o s e j e m p l o s son
tumores c a r t i l a g i n o s o s o g r a s o 5 que se d e s a r r o l l a n e n una
g l a n d u l a por e j e m p l o 1a g l a n d u l a c a r o t i d e a .
Un tumor m a l i g n o o sarcoma d e tina masa c a r n o s a d e r i v a d a d e l
t e j i d o conectivo.
Un tumbi- benigno,no tiene e f e c t o s dahinos,
e x c e p t o e n q u e producen pi-esion d e b i d o a su crecimiento.
El
tumor m a l i g n o no e j e r c e p r e s i t i n e n el t e j i d o a d y a c e n t e , s i n o
Que
l o i n v a d e y l o d e s t r u y e o d e s i n t e g r a , y produce nuevos tumores e n
o t r a s p a r t e s d e l c u e r p o es una c o n d i c i t i n llamada metastasis.
El
sarcama d e l a s f i b r a s n e r v i o s a s e5 l l a m a d o f i b r o n e u r o s a r c o m a ,
y
tambien
encontrado e n t e j i d m l i n f d i d e y g r a s o y para d e t e c t a r l o
se usa l a b i n p s i d i e s el d i a g n o s t i c o p o r examen m i c r o s c o p i c o d e un
t r o z o d e t e j i d o d e l tumbr).Viw r e f . 1 e F.
E l cancer,
es un anormal y a menudo i m p r e v i s i b n l e c r e c i m i e n t o d e
celulas.
L a s neoformacionea c a n c e r o s a s poseen l a p r o p i e d a d
de
invadir
l o s t e j i d o s n o r m a l e r que pueden d e s t r u i r o r e m p l a r a r con
~ L I anarquico
d e s a r r o l l o, y e n s u c a r r e r a d e s e n f r e n a d a d pueden
a f e c t a r a los nervios,producir dolor,
a los v a s o s s a n g u i n e o s que
rompe, p r o d u c i e n d o h e m o r r a g i a s a io5 t e j i d o s pulmo
n a r e s , a r t e r i a s , r i n o n e s y v e j i g a que o b s t r u y e n a l i n f i l t r a r s e
y
lo
mas
s u c e p t i b l e a iie
invasitin
cancerosa,
ron
el
estomago,intestinos,pulmones y o r g a n o s s e x u a l e s i v e r ref .D).
DONDE ATACA E L CANCER
Hombres
Mujeres
(%)
(%)
2.5
5.3
11.9
piel
1.5
boca
1.2
aparato respi ra t o ri o
3.2
mamas
18.2
51.5
aparato d i g e s t i v o
40
12.6
aparato g e n i t a l
24.9
6. 3
aparato u r i n a r i o
3.3
9.9
o t r a s partes
7.7
Se s a b e que hay r e l a c i t i n entre l a s hormonas s e x u a l e s y el
d e s a r r o l l o d e l c a n c e r , e s p e c i a l m e n t e e n el d e l a 5 mamas y o r g a n o s
genitales.
Rara v e z
l a 5 esposas del
circunciso a p a r e c e el
cancer,de
c e r v i x por que en el o r g a n o d e l i n c i r c u n c i s o r e t e n g a
alguna s e c r e c i o n c a n c e r l g e n a e n el p r e p u c i o . (Ver ref .E21
Diagnostico;
U n o d e 105 matodos mas r e c i e n t e s en el campo d e l
d i a g n o s t i c o es l a prueba d e F a p a n i c o l a o u s , q u e p r e v e e l a toma d e
r a s p a d u r a s s u p e r f i c i a l e s d e l c u e l l o uterino d e l a s p a r e d e s d e l a
v a g i n a y son t r a t a d a s con s u s t a n c i a s q u i m i c a s y c o l o c a d a s e n
la
platina y ver
si
hay o n o p r e e s n c i a d e p r e c o s e s cambios
c a n c e r o s o s , l a prueba puede ,ampliarse a e s p u t o 5 o j u g o s g a s t r i c o s
cuando se sospecha d e un tumor e n el
estomago o pulmbn. ( v e r
ref .R).
Rronscoscopia;
Se
i n t r o d u c e un t u b o l a r g o e n l a s e s t r u c t u r a s
pulmonares p a r a tomar t e j i d o s por g a s t r o s c b p i a , hecha con un t u b o
e n el esto mago,^ l a r e c t o s c a p i a e n el que se hace p e n e t r a r e n e1
r e c t o un instrumento p a r e c i d o a un a n t e o j o , y estos a p a r a t o s van
p r e v i s t o s d e l u z que p e r m i t s " v e r " a l o b s e r v a d o r el i n t e r i o r
de
l o s organos.
L.os r a y o s X,
l a introduccion
de bario,
e n el
11
estomago o r e c t o f a c i l i t a r a
cual qui er p o s i b l e tumbr
.
el
reconocimiento
al
siluetear
Tratamiento;
La o p e r a c i a n
q u i r u r q i c a puede proporcionar
al
p a c i e n t , e l a c u r a t o t a l e n un tumor l o c a l i z a d o , e n muchos t i p o s d e
c a n c e r d e p e l v i s se emplea l a R a d i o t e r a p i a , a b a s e d e r a y o s X.
La
t e r a p e u t i c a q u i m i c a , e s l a administr-acibn d e hormonas en el c a n c e r
d e mamas y
prostata,
y d e drogas e n l a leucemia o cancer d e
sangre,y a v e c e s se combinan l a c i r u g i a , l o s rayosX y l a s d r o g a s ,
105 i s n t o p o s r a d i a c t i v o s s u s t a n c i a s
que poseen r a d i a c t i v i d a d
combinada
con el elementos iquimicos,ei p r e p a r a d o q u i m i c o d e g a s
mostaza,creado
con f i n e s b e l i c o s , h a ayudado a destruir c e l u l a s
cancerosas en
l a sangre,
el yodo r e d i a c t i v o í p a r a c a n c e r d e
t i r o i d e s ) , f o s f o r o r a d i a c t i v o ( p a r a v e r r u g a s y l u n a r e s externos).
I...a r a d i o t e r a p i a se usa p r e f e r e n t e m e n t e e n c a n c e r d e p i e 1 , l a b i o s y
cervix.
Terapeut.ica hormonal;
es is1 t r a t a m i e n t o que c o n s i s t e e n l a
e x t i r p a c i b n d e g l a n d u l a e s e x u a l e s y a v e c e s d e l a s adrenales para
e l i m i n a r l a f u e n t e d e l a s hormonas que e s t i m u l e n el d e s a r r o l l o d e
t a l e s canceres.
E l c a n c e r #de p r o s t a t a , s e
a d m i n i s t r a n hormonas
se:.:uales f e m e n i n a s p a r a n e u t r a l i z a r l a a c c i b n d e l a s hormonas
masculinas.
En el cancBr d e mamas a l c o n t r a r i o q u e en e l d e
p r o s t a t a e n mujeres p r e m e n o p ñ u s i c a s y eri 1a5 postmenopausi cas se
u t i l i z a n hormonas femenina's.
En l a q u i m i o t e r a p i a ,
algunas
el metotrexato
s u s t a n c i a s son e l g a s mostaza, l a mercaptopurinab,
y dos p r o d u c t o s d e l a r g a denNDminacion que son TEN y .TEPA.
LA FIERRE;
Elevacibn
anormal d e l a temperatura e n e l
cuerpo
humanoihipertermia) , que se p r e e s n t a a c o n s e c u e n c i a d e l estimulo
d i r e c t o d e l o s centros t e r m o r r e g u i a d o r e s c e r e b r a l e s s i t u a d o s e n
el
tuber
cinereum
y
en
105
nucleos
anteriores
del
hipota1amo;estos
centros mantienen
l a temperatura d e nuestro
organismo,en c u a n t o asegirran el. e q u i l i b r i o e n t r e l a produccibn d e
calor ( t e r m o g e n e s i s ) y l a d i s p e r s i o n der1 mismo h a c i a el ambiente
e x t ern0 ( t ermod i spersi bn )
En
e.fecto,
de
estos
centros
termorreguladores
c e r e b r a l es
parten
los impulsos
de
dos
ordenes,los ciales,a
t r a v e s d e l s i s t e m a n e r v i o s o v e g e t a t i v o ysubsidiariamente-a
traves
del
sistema
enaocrino
(hormona
t i r o i d e a , s o b r e t o d o ) , i n + luyeri poderosamente s o b r e :
-los procec.os t e r m o g e n e t i c o s í p r o d u c t o r e s d e c a l o r ) consti t u i d o s
por
todas aquellas reaciones d e l
metabolismo o r g a n i c o , q u e
se
denominan e x o t e r m i c a s por que se l l e v a n a efecto con e l i m i n a c i b n
d e c a 1 o r ; s o n r e a c c i o n e s d e n a t u r a l e z a prefer-entemente e x u d a t i v a s
que t i e n e n l u g a r sobre todo e n el h i g a d o y eri los musculos;
-y s o b r e l o s p r o c e s o s t e r m o d i f u s o r e s , q u e son tres p r i n c i p a l m e n t e :
l a v e n t i l a c i b n pulmonar (con a i r e e s p i r a d o se e l i m i n a vapor acuoso
c a l i e n t e y , p o r i o t a n t o , c a l o r ) , l a s e c r e c i b n s u d o r a l icon sudor- se
e l i m i n a tambien o t r a f r a c c i o n d e c a l o r i n t e r n o ) y s o b r e t o d o l a
d i l a t a c i a n d e 105 v a s o s s a n g u i n e a s . s u p e r f i c i a l e s c u t a n e o s i q u e
producen el c o n s i g u i e n t e aumento d e l a f l u j o . sanquineo c a l i e n t e d e
l o s organcis internos a l a p i e 1 , e n
l a que t i e n e l u g a r
la
d i s p e r s i o n e n el ambiente e x t e r n o d e l c a l o r t r a n s p o r t a d o por
la
sangre.
Segun Meyer,
el p r i n c i p a l c e n t r o ter-morregulador d e l
hipotalamo
esta constituido:
.
12
-por
un c e n t r o d e l c a l o r que t i e n d e a e l e v a r
l a temperatura
c o r p o r a l ,estimulando
por
una
p a r t e l o s procesos
de
l a
termog&nesis
y,por
o t r a parte,
deprimiendo
los
procesos
termodifusores~mediante
el
siguiente
mecanismo
triple:
d i s m i n u c i b n de l a f r e c u e n c i a y de l a a m p l i t u d r e s p i r a t o r i a , o sea,
de l a v e n t i l a c i b n pulmonar;
i n h i b i c i d n de l a s e c r e s i b r i sudoral;
c o n s t r i c c i d n d e l c a l i b r e de l o s vasos sanguineos cUtaneOS,con l a
consiguiente disminucidn d e l
a f l u j o sanguineo c a l i e n t e a l a
s u p e r f i c i e c o r p o r a 1 , l o que provoca una e l i m i n a c i b n menor de c a l o r
a t r a v e s de l a p i e l ) ;
-.por
un c e n t r o de f r i o que t i e n d e s e n cambio a a l t e r a r - l a
t e m p e r a t u r a c o r p o r a l ,disminuyendo p o r un l a d o l o s procesos de la
termoghesis y
por
el
o t r o e s t i m u l a n d o l o s procesos de
la
termodifusidn
(aumento de l a v e n t i l a c i b n pulmonar,aumento de l a
s e c r e c i d n s u d o r a l , d i l a t a c i h n d e l c a l i b r e de l o s vasos sanguineos
cutaneos,con e l c o n s i g u i e n t e aumento de a - F l u j o sanguineo c a l i e n t e
a l a s u p e r f i c i e c o r p o r a 1 , l o que provoca una mayor e l i m i n a c i b n de
c a l o r a t r a v e s de l a p i e l ) .
Moderna concepcidn p a t o g e n i c a de l a f i e b r e . Hasta hace ~ i n o sahos l a f i e b r e se consideraba como un fenomeno de
origen periferico,en
el
s e n t i d o de que el
aumento de
l a
t.emperatura c o r p o r a l
no t e n i a su o r i g e n en el sistema n e r v i o s o
c e n t r a l , s i n o en l a s p e r i f & i a , m e d i a n t e
e l aumento d i r e c t o de io5
procesos de t e r m o g h e s i s en e l
seno de algunos organos y
tejidos(higado,muscrilos)
y
mediante l a d i s m i n u c i b n de
105
procesos t e r m o d i f u s o r e s
a
n i v e l de io5 p u l m o n e s i v e n t i l a c i b n
y de l a p i e l ( s e c r e c i b n s u d o r i p a r a , i r r a d i a c i ¿ m de c a l o r
pulmanar)
a t r a v e s de l a s u p e r f i c i e c u t a n e a ) .
En cambio,hoy en d i a , l a c a s i
t o t a l i d a d de 1 0 5 i n v e s t i g a d o r e s concuerdan en a f i r m a r
que la
f i e b r e e s un fenomeno de o r i g e n n e r v i o s o c e n t r a 1 , c o n s e c u t i v o a un
e s t i m u l o d e l o s c e n t r o s t e r m o r r e g u l a d o r e s por- p a r t e de 105
agentes e s p a c i a l e s p r o d u c t o r e s de l a . f i e b r e ( d e lo que hablaremos
1uego);este
e s t i m u l o se r e s u e l v e en un aumento d e l a temperatura
CL
f i . e b r e cuando l o s c e n t r o s r e g u l a d o r e s c e r e b r a l e s
corporal
elevan e l
p u n t o t e r - m i c o i g r a d o de temperatura) ,a cuyo n i v e l
se
e s t a b l e c e normalmente(e5 d e c i r , e n
un organismo no f & b r i l ) l a
termorregulacibn,o
sea,
el
e q u i l i b r i o e n t r e 105 procesos de
termog8nesis y 105 d e t e r m o d i f t i s i o n p e r i f e r i c a .
Es d e c i r ,
segdn l a concepcian a c t u a 1 , l a f i e b r e se d e b e r i a a un
proceso de r e a j u s t e d e l p u n t o de t e r m e r r e g u l a c i b n o r g a n i c a a un
nivel
ma5 elevado que en c o n d i c i o n e s norma1es;esta e l e v a c i b n 5e
e f e c t u a r i a en 105 c e n t r o s t e r m o r r e g u l a d o r e s d e l
hipotalamicos
sometidos a l e s t i m u l o d i r e c t o de c i e r t o s f a c t o r e s p i r e t o g e n o s , l o s
cuales,
al
excitar
dichos centros cerebrales,provocarian
la
a p a r i c i o n de l a f i e b r e .
E s t o s e s t i m u l o s p i r e t o g e n o s pueden ser:
-mecanices, como e5 l a comprension e j e r c i d a sobre d i c h o s c e n t r o s
termorreguladores
p a r l a masa de un tumor b a s i l a r d e l c e r e b r o o
l a sangre extravasada d e una hemorragia c e r e b r a l
(especialmente
d e l t e r c e r v e n t r i c u 1 o ) ; p o r eso l a f i e b r e que se observa en muchos
Cd505
de tumores y de hemorragias c e r e b r a l e s debe c o n s i d e r a r s e
como de o r i g e n m k a n i c o ;
-qui m i C 0 5 (mucho ma5 numerosos) y que c o n s i sten:
i ) e n prodctctos de d i s t i n t a i n d o l e y e s t r u c t u r a d e r i v a d o s
de
l a
L _
r
.
e5c is i on
proteica(a1buminosas
peptonas,polipeptido~,aminobases,etc.);productos
que
forman,por
ejemplo,en l a d e s i n t e g r a c i o n de l a s p r o t e i n a s de
se
io5
t e j i d o s quemadosífiebre de l ~ quemaduras
s
de una c i e r t a e x t e n s i o n
y
p r o f u n d i d a d ) y por l a l i o s i s de 105 cuerpos m i c r o b i a n o s i f i e b r e
de
naturaleza
s e p t i c a que se p r e s e n t a en
las
diversas
enfermedades i n f e c c i o s a s g i i n e r a l e s o en los procesos s e p t i c o s
1oca1 e s ) ;
2)
en
s u s t a n c i a s de i n d o l e d i v e r s a
i n t r o d u c i d a s desde
el
exterinr:es
p o r ejemplb c l a s i c a l a a c c i o n . f e b r i l d e l c l o r h i d r a t o
de t e t r a - - h i d r o n a f t i l - a m i n a , d i s l que b a s t a i n y e c t a r un c e n t r i m e t r o
c u b i c n de una
s o l u c i o n acuosa a l "J% en un c o n e j o p a r a que
rapidamente se
e l e v e su t e m p e r a t u r a h a s t a 44$C.
Entre l a s
s u s t a n c i a s c o r r i e n t e s capaces de provocar f i e b r e e s t a e l c l o r u r o
de sodio ( f i e b r e por l a s a l ) .
HIPERTERMIA FEBRIL O ND FEBRIL.Pero no t o d a s l a s h i p s r t e r n i a % ( e %d f c i t - , nri todos los aumentos de
la t e m p e r a t u r a c o r p o r a l i n t e r i : por encima de l o norma1,que en e l
orgaiRffimo humanos se c o n s i d e r a de 37SC) se r e a l i z a n p o r
el
nervioso
central
de
l a
fiebre;cabe,por
lo
m u a n i0 0
tanto, d i f erenci ar :
- l a h i p e r t e r m i a de o r i g e n n e r v i o s o c e n t r a l o h i p e r t e r m i a f e b r i l o
fiebre:
es
a q u e l l a en l a que e l
aumento de l a . t e m p e r a t u r a
corporal
debe c o n s i d e r a r s e como un r e a j u s t e d e l
p u n t o de l a
t e r m o r r e g u l a c i o n a un n i v e l
termico-o
sea,
a un grado de
temperatura-mas
elevado que e l normal;
es l a consecuencia de un
e s t im u 1 o d i r e c t o de 1 0 5 c e n t r o s t e r m o r r e g u l adores c e r e b r a l es
h i p o t a l a m i c o s p o r c i e r t o s fasctores macanicos o quimicos;
-la
h i p e r t e r m i a de o r i g e n p e r i f e r i c o , h i p e r t e r m i a no, f e b r i l
o
hipertermia.
simp1 e:
es
a q u e l l a en
l a que
e l ' mecanismo
p a t o g e n e t i c o debe buscarse nso en el s i s t e m a n e r v i o s o c e n t r a l s i n o
en l a p e r i f e r i a j e n e s t e caso el aumento de l a temperatura
los
corporal
e s t a provocada p o r
f a c t o r e s que o b s t a c u l i z a n
procesos de t e r m o d i s p e r s i a n a t r a v e s de l a s u p e r f i c i e cutanea,con
e l c o n s i g u i e n t e acumulo en e l i n t e r i o r de n u e s t r o organismo de un
c a l o r que d e b e r i a e l i m i n a r s e en c o n d i c i o n e s normales.
El
ejemplo c l a s i c o
d e h i p e r t e r m i a no f e b r i l es el
Golpe de
c a l o r , e n e l c u a l e l aumento d e l a temperatura c o r p o r a l se produce
l a grave d i f i c u l t a d de l a d i s p e r s i b n t r a n s c u t a n e a d e l
calor
por
n r g a n i c n i n t e r n o a l ser e l ambiehte e x t e r n o muy c a l u r o s o ( s o b r e
t o d o cuando e x i s t e tambien 'humedad;en e f e c t o l a humedad e x c e s i v a
del
ambiente o b s t a c u l i z a e l fenomeno de l a sudoracibn y por
lo
t a n t o l a e l i m i n a c i o n p o r d i c h a v i a d e l c a l o r i n t e r n o ) . V e r t-fsf.de
t i p o s de f i e b r e y causas.
UN A R B ü " T 0 ESPECIAL EN HIPERTERMIA Y TERAPIA DE CCINCER.t o d o s sabemos el
cancer e s l a segunda causa de muerte
desesos
del
corazbn,de
hecho
unicamente
excedida
por
aproximadamente de cada c u a t r o personas una puede c o n t r a e r cancer
en a l g u n p u n t o d u r a n t e su v i d a . Y debido a l tremendo e s f u e r z o
c e r c a de l a m i t a d d e l
total
de los
dedicado a e s t a cura,
p a c i e n t e s s o b r e v i v e de l a s v a r i a s enfermedades c a t e g o r i z a d a s es
cancer.
Llna forma
de h i p e r t e r m i a de cancer
es que t i e n e
Como
14
I
c
F
i
r
i
recibimiento
y
r e s u r g i m i e n t o d e un
r e c i e n t e e s t u d i o en
los
u l t i m o s ahos es el u s o d e l c a l o r p a r a o r i g i n a r
temperaturas
e l e v a d a s en el
t u m o r e n el. r a n g o d e 4 2 - 4 5 X y q u e es l l a m a d o
h i p e r t e r m i a ( v e r ref . A ) .
En c i e r t o s e n t i d o , e s t o es un p r o b l e m a i n q i e n e r i l e n el d e s a r r o l l o
de
metodns
d e calentamiento,monitoreos
termai,tratamientos
planeados y
d e t e r m i n i a c i o n termal no son t r i v i a l e s p e r o n u n c a
tratables.
T o d o s l o s a s p e c t o s r e q u i e r e n d e la mas m o d e r n a
t e c n o l o g i a d i s p o n i b l e d e un r a n g o a m p l i o d e d i s c i p l i n a s f i s i c a s e
i n g i e n e ~ i l e s , e s ' t a m b i e n d e acceso i n t i m o p a r a p e r s p e c t i v a s
biologicas y
m e d i c a s p a r a g u i a r l o a en s u d e s a r r o l l o .
Hay
alrededor
de un n u m e r o d e sistemas c o m e r c i a l m e n t e d i s p o n i b l e s
b a s a d o s e n muy d i f e r e n t e s p r i n c i p i o s e l e c t r o m A g n e t i c o s , y
muchos
d e estos sistemas s o n o r i g i n a l e s y son i n v e s t i g a d o s y p r o b a d o s e n
u n i v e r s i d a d e s y c e n t r o s mediilos.
D e b i d o a l o s t r e m e n d o s e s f u e r z o s es l a o p i n i o n u n a n i m e d e este
editor
que
en
l a m a y o r i a de 105 casos c l i n i c 0 5
h a y Sistemd5
i n m o v i 1es y d i s p o n i b l e s q u e p u e d e n p r o d u c i r , o d a r
distribuidores
d e t e m p e r a t u r a ( o c o n t r o l a d o r ) , e n un r a n g o d e 42--45LCe n el t u m o r
s i n c a l e n t a r s e el t e j i d o n o r m a l .
Hay una
anecdota promisoria
interesante
d e l o s r e s ~ l t ~ a d o sd a t o s s o l i d o s q u e i n d i c a n un
beneficioso
positivo terapeutico de l a
hipertermia,y
son
u n i c a m e n t e o b t e n i d o s p o r p r i ~ e b a s . La e f i c a c i a d e l a h i p e r t e r m i a
es una moda.1idad c l i n i c a , b a s t a q u e e l c a l o r d e l sistema l l e g u e a
un g r a d o d e s o f i s t i c a c i d n qiue e s t a d a d a e n el d e s a r r o l l o c l i n i c 0
e n el c u a l p u e d e p r o d u c i r - una d i s t r i b u c i b n d e l a t e m p e r a t u r a e n
t u m o r e s e l c u a l es d e 42$C D mas.
En g r a n p a r t e , l o s sucesos o un
f r a c a s o dE: l a h i p e r t e r m i a p i i e d e . s e r una m o d a l i d a d d e cancer
en
r e p o s o en
l a s manos d e un i n g e n i e r o o f i s i c o , y s u h a b i l i d a d a
resolver ic15 p r o b l e m a s e x t r e m a d a m e n t e d i f i c i l e s d e l a e f e c t i v i d a d
d e 105 t u m o r e s p o r c a l e n t a m i e n t o e n un t i e m p o d e t e r m i n a d o e n el
t e j i d o normal.
Uno d e l o s p r o b l e m a s c r i t i c o 5 e n el campo d e la h i p e r t e r m i a es el
diseno,desarrollo
y p r ~ i e b a sd e m e j o r a r el e q u i p o y los sistemas
de hipertermia.
Los p r i m e r o s d o c u m e n t o r ( 3 ) , s o n
intentos para
p r o v e e r mas d e un c o n j u n t o b i o l o g i c 0 y d a r i m p o r t a n c i a a l
fluido
s a n g i t i n e o b a j o el
problema
de transferencia de calor,y
las
propiedades electricas d e l t e j i d o .
Hay v a r i o s sistemas y
que
s o n ; a m p l i f i c a d o r e s e l e c t r o m a g n e t i c o s s e g u i d o s p o r d o s sistemas d e
t i l t r a s o n i da, dosimetri a termal, los p r i m e r o s d o s conti e n e n
modelos
d e computadora y
105 d o s u l t i m o s e n sistemas d e m e d i c i o n
de
temper a t ura.
HIPERTERMIA PAR6 LA INBIMRIA: UN CORTO COMPRENDIO BIOLOCIC0.-
E l c o n c e p t o coman de el c e n t r a d e t r a t a m i ' e n t o d e cancer a l r e d e d o r
d e l a n e c e s i d a d p r e f e r e n t e m e n t e d e i r e l i m i n a n d o l a s celulas
malignas.
L.a h i p e r t e r m i a p u e d e o f r e c e r un m e d i o d e h e c h o s i , n o
por
que
el
m e d i o i i s i c o e n el c u a l muchas c e l u l a s d e los t u m o r e s
pueden
e n c o n t r a r s e e l l o s mismos y
son solidos.
La p r i v a c i b n
nutricional ,bajo
ph,
y
una h i p o x i a c r o n i c a c a r a c t e r i z a a l
interior
de muchos t u m o r e s y e s t a s c o n d i c i o n e s q u e e n t r e g a
tambien
l a s e n s i b i l i d a d d e l c a l o r en
las celulas.
El
calor
t a m b i e n e n g r a n d e c e l a e f e c t i v i d a d d e i r r a d i a c i o n X,
y agrandando
t-
g r a d o s ma5 a r r i b a ,
l a s c a l e n t u r a s t a m b i e n p u e d e n i n h i b i r y mas
d e s p a c i o y p o r o t r a p a r t e en l a m u l t i p l i c a c i o n d e a l g u n o s v i r u s .
Pero n o s 0 t . r - o s s i m p l e m e n t e n o es s e g u r o y a sea,
p o r q u e n o sea
c u a l q u i e r a d e e s a s e n c o n t r a r e m o s y que s o n r e a l m e n t e p a r a el
16
b
e s t e metodo l a emplean en el t r a b a j o de i p e r t e r m i a y t r a b a j a n par
atener
un minimo de algunos n i v e l e s de e n t e n d i m i e n t o de b i o l o g i a
termal.
I
.i
c
I
-
C
c
i
c
L
r
i
ir
c
b
P
L a i m p o r t a n c i a d e l e s t u d i o de l a s c e l u l a s ;
el
tratamiento
del
cancer comun se c o n c e n t r a en l a e l i m i n a c i b n de c e l u l a s malignas y
es p o s i b l e que un pequena p a r t e v i t a l d e l t e j i d o sea dahada.
La
c i r t q i a remueve l a s c e l u l a ' s cancerosas p o r
afeccibn cortante
h a c i a afuera
de l o s volumenes de t e j i d o ;
l a l i m i t a c i o n de l a
c i r á g i a es que p a r t e s no v i t a l e s de l a anatomia pueden s e r
removidas. Los t e r a p e u t a s de r a d i a c i b n matan c e l u l a s m a l i g n a s p o r
Aqui
el
e x p o s i c i o n p a r a l a s d o s i s de l e t a l e s de r a y o s X.
t r a t a m i e n t o , e5 l i m i t a d o p o r l a r e s p u e s t a de el t e j i d o normal
son
e l volumen d e l t r a t a m i e n t o ,
l a s drogas a n t i c a n c e r o s a s tambien en
el
a c t o e l i m i n a n l a s c e l u l a , ~malignas i n d i v i d u a l e s .
Por que l a
naturaleza sistemica del
t r a t a m i e n t o de l a droga e l
tejido
l i m i t a n t e e5
e l sistema c e l u l a r mas s e n s i t i v o p a r a una droga
p a r t i c u l a r usada,
l a i p e r t e r m i a tambien mata c e l u l a s y p a r a l a
calefaccibn
lwcalizamos
i en c o n t r a s t e p a r a el
calentamiento
e5 l a r e s p u e s t a d e l t e j i d o normal
s i n el
i n t e g r o d e l cuerpo),
volumen de c a l e n t a m i e n t o que d e c i d e l a d o s i s de c a l o r que puede
s e r aplicadw.
En mas s i t u a c i o n e s e s t a es r e l a t i v o p a r a matar l a s
c e l u l a s malignas y
e s p e c i f i c a s normal q u e suceda determina o
f a l l a de e l p r o t o c o l o d e l t r a t a m i e n t o .
Dosis
de c a l o r ;
Fundamental par-a una c u a n t i f i c a c i b n de un
fenomeno b i o l o g i c 0 es l a d o s i s en l a c u r v a de respuesta.
For
ejemplo en e l caso i r r a d i a c i b n X,
l a s r e s p u e s t a s r e l a t i v a s en l a
curva
l a
c a n t i d a d de e n e r g i d a b s o t i v a p o r
las
celulas
supervivientes.
Para l a h i p e r t e r m i a e s t o es fundamental que l a s
dos c a n t i d a d e s s e a n . d e impor-tancia i g u a l en l a d e t e r m i n a c i b n de
l a p r o b a b i l i d a d de s u p e r v i v e n c i a de algunas c e l u l a s ,
e s t a s son
t e m p e r a t u r a y t i e m p o ( @nl a t e m p e r a t u r a ) .
E s t a r e l a c i b n e n t r e s u p e r v i v e n c i a de c e l u l a s y esos parametros no
l i n e a l e s ( REF d e l
mismo f i g . l ) ,
y p o r eso no hay una s i m p l e
v a r i a b l e f i s i c a de combinacibn l i n e a l de v a r i a b l e s que pueda ser
i d e n t i f i c a d a que pueda d e f i n i r una d o s i s de c a l o r ,
rango,
un
r e g i s t r o d e tiempo y t e m p e r a t u r a que n e c e s i t a ser
provisto.
La
necesidad de una d e f i n i c i b n de d o s i s de c a l o r es una de 106
u r g e n t e s r e q u e r i m i e n t o s en l a h i p e r t e r m i a c l i n i c a ,
l a d o s i s de
r e s p u e s t a en l a f i g , e a mas complicada p o r el h a l l a r mas c e l u l a s
diferent.emente conducida a temperaturas a b a j o de 451C que es l a
t e m p e r a t u r a b a j a en l a f i g .
L O 5 parametros ;
en l a s c e l u l a s t i e n e n c o n d i c i o n e s estandares, y
son a b a s t e c i d a s con n u t r i m e n t o s de oxigeno,
t e m p e r a t u r a de 37SC y
un
PH d p t i m o excepto cuando aumenta l a temperatura
esas
c o n d i c i o n e s no p r e v a l e t e n en e l i n t e r i o r de muchos tumores.
Hay
n u t r i e n t e s y oxigeno e x i s t e n t e s unicamente l i m i t a d o s y PH menor
que en e l t e j i d o normal.
L.os experimentos muestran una b a j a de
n u t r i e n t e s , h i p o x i a c r o n i c a y b a j o PH, y t o d a s t i e n d e n a hacer
que l a s c e i u l a s Sean s e n s i t i v a s a l
calor.
Muchos e s t u d i o s
muestran que l a s c e l u l a s mas s e n s i t i v a s son l a s c e l u l a s normales
o similar-iis,
es verdad que p o r medios l a r g o s de tiempo l a s
c e i u l a s pueden ser e l i m i n a d a s y puede el p a c i e n t e ser curado.
17
O
1s
45
75
w
de c a l o r
multiple,
una p a r a d o j a ;
En l a s c l i n i c a l a
hipertermia
l o c a l i z a d a n o d a una dos15,
p e r o el tratamiento es
fraccionado
por t e r a p i s t a s (en c u r s o s d e r a d i a c i b n X.
Siempre el
t r a t a m i e n t o i n i c i a l empieza
t e m p e r a t u r a s mas b a j a s d e 4StC, l a s
c e l c i l a s muchas v e c e s son ma!% rtesistentes a l
calentamiento,
si
l a s c e l u l a s son t y r a t a d a s a 43C o mas se r e g r e s a a l incubador
de
37#C.
Esto es por
l a re!;puesta d e l a s c e l u l a s a m u l t i p l e s
tratamientos de c a l o r ,
aqui hay un c u r i o s o t r a t a m i e n t o ,
si
la6
c e l u l a s son t r a t a d a s a una temperatura d e 43tC o mas p o r un corto
tiempo de tratamiento,
si l a s c e l u l a s s u p e r v i v i e n t e s p a r a unos
POCOS
(menos d e 4 ) ,
son inas s e n s i t i v a s p a r a el t r a t a m i e n t o
subsecuente a b a j a temperatwra ( s t & p - d o w n ) .
E l c a l e n t a m i e n t o e x c e s i v o e n el comienzo d e el t r a t a m i e n t o cuando
por
p o c o s minutos p u e d e 5er t r a t a m i e n t o d e b a j a temperatura,
y
por
eso para una i n e s p a r a d a t o x i c i d a d a s o c i a d a por f a s e s e n l a
de
l a s celulas.
Mas,
importantemerite
el
sendo
mueryte
Calentamiento,
d u r a n t e q u e l e p a c i e n t e se a p r e s u r e .
Esto es
i m p o r t a n t e ya que el c a l e n t a m i e n t o e s r-apido,
y cuando n o es
p o s i b l e en que l a t e m p e r a t u r a d e d i s t r i b u c i b n e n tumores y t e j i d o
limite bien
definido,
la
normal
para
c o n t r o l a r con un
t e r m o t o l e r a n c i a puede ser c o n s i d e r a d a cuando l o s p r o t o c o l o s f i s i
camente d e s i g n a d o s p a r a el t r a t a m i e n t o f r a c c i o n a d o .
La h i p e r t e r m i a y l o s e f e c t o s d e r a y o s X y d e c i e r t a s drogas;
Un
r a t o d e t r a t a m i e n t o con c a l o r p o r que e l l o s mismos son d e U50
p a r a o t r o s tumores a c a s o l a yran a t r a c c i o n p a r a l a h i p e r t r m i a
es
ofrecer
uno que es mas e f e c t i v o y engrandece a muchos otros
a g e n t e s drat i c a n c e r o s o s .
Los ejemplos s e v e r o s e s t a n mostrados e n
la fig.
2, ( d e l mismo a r t i c u l o ) . Tal v e z el mas g r a n d e p o t e n c i a l
y c i e r t a m e n t e d e uso mas c o r r i e n t e ,
e5 el s i g e r g i s t a entre el
calor
y l o s r a y o s X.
La t e r a p i a d e r a d i a c i b n es el segundo mas
angular
usada como arma a n t i c a n c e r y un metodo p a r a h a c e r esto
ma5 e f e c t i v o puede ser t r a t a d o e n un r a n g o i n p r o v i s a d o p a r a
curacibn.
Eso se muestra e n l a f i g . 2 ,
el c y t o t b x i c o d e r a y o s X
apreciablemente
incrementando sus c e l u l a s son expuestos p a r a
elevar
l a temperatura a n t e s d e o t r a s i r r a d i a c i o n e s .
Despues d e
mil
rads,
d e rayos X
en cien,
sin c a l e n t a m i e n t o s o b r e v i v e n
c e l u l a s pero unicamente 1 e n 10,C)CiCi d e l a s c e l u l a s s o b r e v i v e a l
calentamiento.
Otro camino es observando 105 d a t o s e s t a n o t i c i a
hace que aproximadamente 30% menos d e l a d o s i s p a r a morir sea
s i m i l a r a 105 n i v e l e s d e s u p e r v i v e n c i a (0.001) cuando el c a l o r es
ahadidn p a r a l a r a d i a c i o n l a usual t e r m i n o l o g i a es p a r a d e c i r que
e f e c t o t i e n e una d o s i s d e f a c t o r m o d i f i c a d o d e 1.3,
l a celulas
qLie puede resistir
altamente l a
h i p o x i c a s s o n una muestra
r a d i a c i o n X.
Probabl emente mas tumores humanos c o n t i e n e n e n mas o menos
c e l u l a s h i . p o x i c a s y esto e5 a t r - a v e s y p u e d e 5er r e s p o n s a b l e d e
muchas f a l l a s e n r a d i t . e r a p i a ,
matar c e l u l a s h i p o x i c a s con el
calor
es el mas pequeilo y mas e f i c i e n t e y es el mejor o x i g e n a d o
d e l a 5 c e l ~ i l a s . De 1150 l o s t e r a p e u t a s pueden unicamente tomar
v e n t a j a d e eso5 b e n e f i c i o s incrementando a 5 i el
dano a 105
t e j i d o s normales y no acentuando i g u a l d a d .
E l camino mas f a c i l
para
acoplar
conceptualmente e5 l a v i a
de
calentamiento
preferencial
d e el volumen d e l tumor-, a s i nosotros r e g r e s a m o s a
la
p r e g u n t a d e que e q u i p o d i s e n a r .
El
c a l o r puede
ser
incrementado
p a r a ayudar a l a m u e r t e d e l a s c e l u l a s y muchas
Dosis
18
,...
BCNU Iicliiwe dosel
(b)
I
05101520
30
40
50
60
I
d r o g a s í f i g . 2b,c y d ) .
La q u i m i o t e r a p i a es usada primeramente p a r a a l g u n o s canceres esto
es cuando se e%pande a t r a v e s d e l cuerpo,
los b e n e f i c i o s d e
tratamientos
l o c a l e s no es o b v i o ,
el uso d e h i p e r t e r m i a f u e un
potencial
considerable.
En
un t r a t a m i e n t o
frecuentemente
encontraremos s i t u a c i o n e s en que una o mas l a r g a s
etapas
d o l o r o s a s e n l a misma v i d a di21 t r a t a m i e n t o p a r a e l i m i n a r l e s i o n e s
y no responde a l a quimioterapia.
Esto es l a combinacion d e un
t r a t a m i e n t o d e c a l o r y a l g u n o s tumores y una t e r a p i a s i s t e m a t i c a
d e d r o g a s p u e d e ser i n d u c i d a e n r e g r e s i o n e s d e e s a s lesiones,
la
aparencia e n
l a combinacion puede ser b e n e f i c o s o tambien e n l a
quimiaterapia
d e los tejido's.
Y a s e a o n o t o d o el c u e r p o puede
a c o p l a r s e por h i p e r t e r m i a y q u i m i o t e r a p i a y
algunos b e n e f i c i o s
pueden ser v i s t o s .
PRINCIPIOS DE MEDICINA F1CICA.-
Este
e s c r i t o describe l a terapeutica y aplicación de energid
f i s i c a e n medicina d e r e h a b i l i t a c i b n .
Esto i n c l u y e t e r m o t e r a p i a
( c a l o r y f r i o ) , r a y o s u1 t r a v i o l e t a ,
electroterapia,
masaje,
mani pul a c i cm d e a l argami e n t a y t r a c c i on.
CALOR;
Lor; p r o c e s o s b i o l o g i c o s p a r a g e n e r a l y son a f e c t a d a s por
e n e r g i a s f i s i c a s , una d e l a s c u a l e s es c a l o r .
Esto es comunmente mas usado e n l a modalidad d e medicina d e
r e h a b i l i t a c i b n y usualmente e5 a p l i c a d a ,
antes de e j e r c i c i o s d e
alargamient,~, O electroterapia.
Esto es empleado p a r a ambas
105
puntas y desordenes c r o n i c o s y los e f e c t o s f i s i o i b g i c o s y
mismos c u a l q u i e r a d e 105 r e c ~ i r s o s ,
v a r i a n d o unicamente la
profundidad d e penetracion.
FICICA; E l c a l o r es p a r t e d e el e s p e c t r o e l e c t r o m a g n e t i c o y es un
e s t a d o d e e c c i t a c i b n d e l a p a r t i c u l a ( e n t r b p i a ) . Todos 105 atom05
o m o l e c u l a s a b a j o d e c e r o g r a d o s K e l v i n tiene e x c i t a c i b n y es
capar
d e t r a n s m i t i r erihrgia p a r a o t r o t i p o d e p a r t i c u l a s por
La e n e r g i d d e t r a n s f e r e n c i a por
d i r e c t a c o l i s i o n o radiacion.
colision
E m s a l i d a s es conduccibn y e n l i q u i d o s o
gases
conveccion.
Esto ocurre unicamente cuando l a p a r t i c u l a e s t a
a b s o r v i e n d o y t i e n e b a j a e n t r b p i a ( t e m p e r a t u r a ) . P o r eso el c a l o r
puede unicamente ser t r a n s m i t i d o d e a l t a s t e m p e r a t u r a s a b a j a s
es l a emision d e f o t b r i e s
(cuantos
temperaturas.
La r a d i a c i b n
paquetes d e e n e r g i d ) ,
con l u g a r e s t r a n s v e r s a l e s y
puede ser
absorvido
(1)
aumenta l a s p a r t i c u l a s en e s t a d o e x c i t a d o ,
(2)
varia
esto en l a quimica,
y ( 3 ) e s t a r e e m i t i d a es c a l o r o luz
íf1uorecent:e y f o s f o r e c e n t e s ) .
La p i e l
es un buen r e f l e c t o r e q u i t a t i v o r a d i a d o r y p o b r e
conductor d e c a l o r .
El
c a l o r es a b s o r v i d o
inmediatamente se
encuentra l a a l t a concentracibn
d e m o l e c u l a s d e agua e n l a
subcutanea c a p i l a r y un l e c h o g r a s o s o ,
los c u a i e s s o n sujetos en
f i s i c a y reacciones f i s i o l o g i c a s .
El
calor
especifico,
l a ganancia d e c a l o r i a s o l a s p e r d i d a s
n e c e s a r i a s p a r a 1 0 5 cambios d e l a t e m p e r a t u r a d e un gramo d e una
substancia,
es por l o t a n t a , aproimadamente grande, p a r a agua que
esto e=. p a r a o t r a s m o l e c u l a s d e l t e j i d o .
El agua subcutanea a s i
v i e n e e n e c e l e n t e s r e e s r v a s almecenadas d e c a l o r o a i s l a d o y
contribuye significativamente
h a c i a el
mantenimiento d e
la
r e l a t i v a t e m p e r a t u r a del cuerpo.
E l c a l a r puede ser a b s o r v i d o e n
19
t e j i d o s potl a coriveccion d e ondas e l e c t r o m a g n e t i c a s
de a l t a
f r e c u e n c i a d e n t r o ( 1 ) d e una pequeha c o r r i e n t e ( o n d a s cortas -0
microondas,
( 2 ) esqui l e o , v i b r a c i o n a l f r i c c i o n a l o ondas mecanicas
d e comprension (U. C. )
Estan d e s c r i t a s e n D I A T E R M I A o "calor- profundo" en su modalidad y
puede
penetrar
al
musci.ilo.
Conductividad,convencional
o
penetracibn
d e c a l o r r a d i a n t e d e 1 a '3 mm.
y es l l a m a d o calor
superficial.
En resumen,
e:l c a l o r es e r i e r g i a e l e c t r o m a g n e t i c a ,
l a s cual
es a b s o r v i d a a vo'luntad ( 1 ) e l e v a r l a t e m p e r a t u r a , ( 2 )
producir
r e a c c i o n e s qriimicas, ( 3 ) t r a n s m i t i r e s a ei-iergia a o t r a
p a r t i c u l a a, ( 4 ) reemitir e n ,si mismaesa l u z y c a l o r .
.
,
EFECTOS FISIOLOGICOS DEL CALOR.L a s funciones f i s i o l o g i c a s son gobernadas por l a s m a n i p u l a c i o n e s
d e e n e r g i a d e m o l e c u l a s e s p e c i a l i z a d a s u s u a l m e n t e p r o t e i n a s en
las c e l u l a s , e s t a membrana y c o m p a r t i m i e n t o s e x t r a c e l u l a r e s . Esa6
m o l e c u l a s tiene mecanica i n l h e r e n t e ,
e l e c t r i c a y e n e r g i a quimica
que e s t a g e n e r a d o O t r a n s f i r i e n d o .
La suma d e e n e r g i a t e r m a l
en
los s i s t e m a s a v o l u n t a d pliiede acumularse en esos p r o c e s o s d e
t,ransduccion.
La e n e r g i d t e r m a l e n l a s m o l e c u l a s d e agua d e el
s o l e n t e acuoso actrra
como una .fi.ier-za d e conduccion d e esas
r e a c i o n e s y puede aumentar- e l moimiento d e o s c i l a m i e n t o cambios o
s e p a r ac i on
de
dipalos
o
producir
cambios
electricos.
Adicionalmente
105
e n l a c e s d e h i d r o g e n o pueden
ser hechos o
r o m p e r l o s y r e s u l t a e n cambios q u i m i c o s d e l a s a l t e r a c i o n e s e n
las
c o n f i g u r a c i n e s molecular
y
atomica.
Esos e f e c t o s son
metabolicos
D
cataliticos y
f u n c i o n e s en l a v i d a s o n los
r e q u e r i m i e n t o s d e s u b s t r a t o e n l a s ~ m l e c ~ i l a s . Nosotros con estos
postu1adDs dar
l a s i g ~ i i e n t e secuencia
d e resultados de
la
aplicacion de calor a l a s celulas:
1 ) aumenta 105 r e q u e r i m i e n t o s
c e l u l a r e s metabolicos y c a t a l i s i s ,
2 ) produccidn d e e n e r g i d d e
3) v a s o d i l a t a c i b n
mnleculas(~xigeno, proteinas y carbohidratos)
y
aumento e n
l a presion c a p i l a r con 4 )
tr-ansudoracidn y d e
a l t e r a c i o n e s d e l a c o n f i y u r - a c i o n d e l a membrana o dinamica 5) d e
bombeo i d n i c o d e e l e c t . r o l i t o s y f l u i d o s .
Continuando con l a s
aplicacionEs o r e d u c c i o n e s d e temperatura puede r e s u l t a r , en
(1)
d e g r a d a c i o n d e p r o t e i n a s c r e a t i n i n a , t i i s t i m i n a y s u b s t a n c i a s , (2)
1e u c o c i t o s y ( 3 ) concumi t a n t e i n f 1amator-i a o a n t i - i n f l a m a t o r i a
r e a c i o n f v r e ref pag.76 d e este mismo a r t i c u l o . )
,
EFECTOS CLINICOS DE EL CALOR.La r e a c i b r i
d e l a p i e l l o c a l m e n t e i n c l u y e sensores d e c a l o r ,
vasndilatacibn
(eritema),
reducidn
en l a sudoracion d e l a
r e s i s t e n c i a d e l a p i e l y aumento e n el metabolismo l o c a l d e l
tejido.
S i el c a l e n t a m i e n t o es c o n t i n u o mas a l l a d e 40 a 60 min,
l a temperat.ura d e l
corazdn p u e d e ser e l e v a d a y
l a respuesta
h o m e o s t a t i c a ,de v a s o d i l a t a c i b n . d i s t a l
ocurre.
U s u a l m e n t e la
temperatura, p u l s o y p r e s i o n sanguinea n o son a f e c t a d a s y s o n los
sistemas r e n a l y g a s t r o i n t e s t i n a l . La v e l b c i d a d d e conduccibn d e l
nervio y
p o t e n c i a l e s d e a c c i o n pueden aumentarse.
E l tono
muscular o t e n s i o n p u e d e a b l a n d a r s e P l a e l a s t i c i d a d aumenta. Los
ligamentos
y f i b r a s caps.1.11ares pueden
similarmente
Qanar
elasticidad,
y movimiento d e aumento d e u n i o n e s .
El
dolor
ocasionalmente a voluntad
puede ser
m i t i g a d o por- c a l o r ,
la
@ > : p l i c a c i o n es p o s i b l e m e n t e r e l a c i o n a d a e n un e j e aferente d e
s a l i d a gama pero aun esto n o es una e x p l i c a c i o n es p o s i b l e m e n t e
relacionada
satisfactoria.
La a c c i b n a n t i - i n f l a m a t o r i a d e c a l o r
incluye
leucocitos,
incremento e n l a prerion c a p i l a r y en loo
e f e c t o s d e l a 5 enzima5 humorales,toda a c c i o n h a c i a l a s u p r e s i b n
d e l a r e a c c i b n d e los t e j i d o s .
La c a n t i d a d , r a n g o y d i r e c c i o n d e
l a g a n a n c i a d e c a l o r e n t e j i . d o s D p e r d i d a es d e p e n d i e n t e d e i d s
siguientes
(1)
o r i g e n d e e s t a temperatura y d u r a c i o n e n
la
aplicacion,
(2) l a s propiedades o p t i c a s d e l a p i e l ,
(3)
el
g r a d i e n t e d e t e m p e r a t u r a e n r a z o n - p i e l , e l c u a l ; v a r i a d e 5$-10tC
dependiendo e n el s i t i o d e pri.teba,
l o s promedios d e t e m p e r a t u r a
d e l corazon
es. d e 37ta 408C!, y e r i l a p i e l d e 298 a 35tC, (4) l a
cantidad
d e agua y g r u e s o e n l a c a p i l a r i d a d subcutanea y capa
gruésa,
( 5 ) i n s c o n t r o l e s neuraies h i p o t a l a m i c o s y
piel,
los
c u a l e s mantienen constante!% l a s mecani5mos d e temperatura,
el
cual
es un r e f l e j o vasomotore e n l a s r e a c c i o n e s d i s t a l en a r e a s
t r a t a d a s , ( 6 ) IDS macariismo!% r e s p i r a t o r i o y
excretorio,
(7)
temperatura
ambiente y humedad y ( 8 ) edad( e n
io5 ancianos e
i n f a n t e s t o l e r a n el
c a l o r b a s t a n t a mal,
5 e x o,
n u t r i c i bin,
e j e r c i c i o , h i d r a t a c i b n , s e n s i b i l i d a d y enfermedad).
Indicaciones:
El
c a l o r e5 i n d i c a d o r d e esos e f e c t o s a n a l g e s i c o s
p r i meramente.
La
aplicacibn
usual
son
de
desordenes
munculoesqueleticos,
neuro,muscular
tales
como
neuralgias,
torceduras,
dislocacion
d i s p a r a d o r d e puntos y el a n f i t r i o n d e
p e r i o d o s que d e s c r i b e el prob1,ema vagamente d e el d o l o r muscular.
Simmons,; e n un e s t u d i o e;:hau5tivo r e v i s o el d o l o r muscular y los
sindromes E? i n t e n t a n d o d e f i n i r l o s los muchos terminos usados p a r a
el
problema y r e p o r t a r l a s c o n d i c i o n e s p a t o l o g i c a s
describir
dadas por una i n v e s t i g a c i b n d e b i l .
Contradicciones;
e l c a l o r todo 1 0 que este r e c u r s o , no puede ser
usado
e n i n f l a m a c i o n e s agudas O traumas u t i 1 e n l a r e a c c i b n
inicial
tiene s u b s i d i o ,
no e n o b s t r u c c i o n venosa
insuficiencia
arterial
o
isquemia,
h e m o r r a g i a s tesis,
O
defectos
de
ccagulacion,
e n l a a u s e n c i a d e c a s o s e s p e c i a l e s d e sensacion,
En
la
presencia
de
fallas
pueden
setexaminados.
cardiovasculares,
respirator-ios o r e n a l e s ,
el c a l o r puede ser
u s a d o con rnoderacion,
el
uso d e c a l o r e n t o d a s l a s a r e a s d e
m a l i g n i d a d s o l i d a es c o n t r a d i c t o r i a ,
a t r a v e s de l a p o s i b i l i d a d
d e o t r a s u p e r f i c i a l o c a l e n t a m i e n t o p r o f u n d o que a f e c t a n a los
tumores y puede ser c u e s t i o n a d o por temperatura.
RECURSOS.- La c o n d u c t i v i d a d por c a l e n t a m i e n t o es l l e v a d a a cabo
por el c o n t a c t o d i r e c t o con l a piel, e n l i q r n i d o s p a r a el c o n t r o l
d e l a t e m p e r a t u r a e n h i d r o t e r a p i a que puede ser r e d u c i d o a
temperaturas d e s e a b l e s D e l e v a r l a s .
CALOR
RADIANTE.- E l c a l o r r a d i a n t e es r a d i a c c i b n
infraroja,
la
cual
t i e n t i una l o n g u i t u d d e 770 a 12,OüOnm,
y
se acerca a l
e s p e c t r o v j , s i b l e (390 a 770rirn). E s t a p r o f u n d i d a d o p e n e t r a c i b n es
aproximadamente d e 10 a 1 mm, d e cei-ca(770 P 150ünm1, y d o 1 a
0.05mm d e l e j o s (i,SOO a lZ,000nm),
los fotones a 1 0 l a r g o a, 1a
l o n g u i t u d d e onda pueden t a n e r e n e r b i a menor anL.-.,
,de p e n e t r a r
lentamente
( t a b l a 3.1
del
a r t i r u l o b ..
ref.)
el
efecto
fisiologico
ric
1 3 r a d i a z i ? m - 50,'; i d e n t i c a s
a los
de
la
cntdctctivida.3 d e c a l o r ( v r e ref ,G, I y d i a g n o s t i c r a d i o l o g y ) .
ULTRCISEIJX30:l o s e f e c t o s f i s i o l o g i c o s d e c o n d u c t i v i d a d y calor-
,
21
>
i
radiante
, ondas cortasímic:roondas), u l t r a s o n i d o y d i d t a r m i d ,
esas i n d i c a c i o n e s y c o n t r a d i c c i o n e s son esncialmonte o1 mismo,
l a 5 c o n s e c u e n c i a s es que l a d i a t P r m i a y u l t r a s o n i d o producen
e f c t o s c l i n i c o s unicamente por produccibn d e c a l o r sin t e j i d o s ,
a t r i b u y e n d o l e s u n o o otrorj efectos,en e s a modalidad es comun
p r e s e n t e n o r e p o r a t a d o por e v i d e n c i a
l a 5 m o d i f i c a c i o n e s d e lo6
descubrimientos
de
esas
energids
por
pulso
o
optras
h i b r i d a c i o n e s , no e5 o t r a qui? esos a g e n t e s t e r m a l e s unicamente.
FRI0.-- l a r e d u c c i d n d e temperatura d e l c u e r p o o p i e l e5 usado
en
medicina d e r e h a b i l i t a c i b n p a r a ( 1 ) a n a l g e s i a l o c a l , ( 2 )
efectos
a n t i - i n f l a m a t o r i o s , 13) h i p o t e r m i a d e c o n t r o l o p i r e x i a o p o s i b l e
control
de plasticidad (ver ref
f isicas,
fisiologicas,
efectos
anti-inflamatorios,
analgesia,
e f e c t o a n t i p i r e t i c o y refE2).
,
HISTDRIA CLINICA
a
NOMBRE DEL PACIENTE
EDAD
DIA
DIAGNOSTICO CLINICO;
DIAGNOSTICO DESEADO;
FORMATO DE TRATAMIENTO;
FRECUENCIA DEL TRATAMIENTO Y DURACION;
ELECTRODO (TIFO U APARATO);
TIPO DE APL.ICACI0N;
INSTRUCCIONES ESPACIALEC;
MD
PRECAUCIONES;
.
REHABILITACION DE PhCIENTE5 CON ENFEREDAD VhsCUuIR PERIFERIAI
referida
e n e s t a d i s c u c i b n a b a r c a l a s enfermedades d e l a s
arterias,
venas y v a s o s l i n f a t i c o s e n l a s e x t r e m i d a d e s ( v e r r e f .
1).
Los p r o c e s o s
d e e s a s enfermedades i n c l u y e n o unicamente
condiciones patologicas s i n
l i m i t a r s e a esos v a s o s pero a s i
muchas c o n d i c i o n e s
i n i c i a l e s e n d i s t u r b i o s d e r e f l e j o e n esos
vasos secundarios e n simpatico, parasimpatico y i n f l u e n c i a s en l a
medttla
espinal.
El
e s t u d i o d e e a s a enfermedades p e r i f e r i a
vascular
r e q u i e r e e s e n c i a l m e n t e l a s mismas t e c n i c a s que uno
genera1ment.e e m p l e a e n l a medicina i n t e r n a : h i s t o r i a , examinacibn
fisica,
y t e c n i c a s d e e-valuacibn e s p e c i a l .
Hay ciertos a s p e c t o s
b a s i c o s en este grupo d e enfermedades que r e q u i e r e un e n f h s i s
especial
e n l a examinacibn y que puede ser o b t e n i d o ,
uno por
sondeo h i s t o r i c o .
Esto e s
p o r l o t a n t o mas i m p e r a t i v o que a
traves
de
un c o n o c i m i e n t o d e l a c i a s i f i c a c i b n
de
esas
enfermedades es mostrada.
Examinacidn;
La examinacidn f i s i c a e n l a s enfermedadss v a s c u l a r
p e r i f e r i c a p u e d e ser
a t r a v e s de,
un a r e a a f e c t a d a .
La
i m p o r t a n c i a d e o b t e n e r un h i s t o r i a a t r a v e s d e un m i n u c i o s o y
de
p r i o r i d a d general
e n un a r e a d e c o n c e n t r a c i o n como traumas,
Es
1
22
diabetes
‘y p r e v i a s t r o m b o c i t o s i s v e n o s a s
o
enfermadades
cardiacas,
es l a misma e v i d e n c i a . C i e r t a m e n t e el c o n o c i m i e n t o e n
una m a l i g n i d a d m e t a s t a s i s existe e n un p a c i e n t e con r e c u r r e n t e s
t r o m b o s i s v e n o s a s que n o responde a a n t i c o a g u l a n t e s es un f a c t o r
p o t ente
gobernante
de
otro
esfuerzo
terapeutico.
El
d e s c u b r i m i e n t o f i s i c o d e una l e s i o n v a s c u l a r m i t r a l a s o c i a d a con
una f i b r i l a c i a n
a u r i c u l a r e n un p a c i e n t e con e v i d e n c i a d e una
oclur;ion
a r t e r i a l aguda puede ser d e una i m p o r t a n c i a soberana e n
el e s t a b l e c i m i e n t o d e b a s e s e t i o l o g i c a s d e el p r e e s n t e sintoma.
For c o n s i g u i e n t e e l uso d e pruebas d e May’s p a r a l a c l a u d i c a c i o n
intermitente,
l e c t u r a s o s c i l o m e t r i c a s , lecturas d e t e m p e r a t u r a y
d e v a r i a s pruebas d e est.ab:i l i d a d vasomotora puede ser empleada
ciiando
indican.
Angi ogrikf i a
y
venograf i a
son
usadas
frecuentemente;
f o t a g r a f i a i n f r a r o j a , p l ei smograf i a y m e d i c i o n e s
d e . f l u j o d e u l t r a s o n i d o dopp:ler tambieri pueden ser usados.
E l ambit0 d e t r a t a m i e n t o s d e enfermedades v a s c u l a r
Trat.amiento;
perifericas
s i n l a d i s c i p l i n a d e l a medicina d e r e h a b i l i t a c i o n
p u e d e ser e l p e r f i l d e l a s s i g u i e n t e s ;
1)
termot er a p i a;
a ) h i per.terini a (
c a l e n t ami ento
directo
e
i n d i r e c t o ) , b)hipotermia y c ) a l t e r a c i o r l d e temperatur~as(contra5te
d e banos).
2 ) el e c t r o t er a p i a;
a ) est i mu1 ac i on d e l muscul o, b ) i ontof oresi 5.
3 ) mecanoterapia;
a l o c l u s i o n intermitente venosa, b ) p r e s i o n d e
s u c c i o n d e un tubo, c ) a l o j a m i e n t o d e o s c i l a c i o n e s , d ) compresion
vaso neumatica, e ) masaje s i n c a r d i a l y f ) masaje.
4) e j e r c i c i o s terapeuticos;
a ) e j e r c i c i o s B u e r g e r , b ) caminado6
t e r a p e u t i c05.
5 ) mediciones p r o f i l a c t i c a s ; a ) general y b ) calzado.
6 ) m e d i c i o n comprensiva d e r e h a b i l i t a c i o n ( v e r r e f . E2).
TERMITERAPI A.
-
Hipertermia;
El i n d u c i m i e n t o d e e p i s o d i o s r e p e t i d o s d e maxima
v a s o dilatacictin d e a l i v i o d e angiosespasmo y d e promocion d e
las
p a r a l e l i s m o es un o b j e t i v o e s t a b l e c i d o e n el t r a t a m i e n t o e n
enfermedades a r t e r i a l e s c r o n i c a s ,
y a s i d e a l g u n o s g r a d o s mas
a b a j o e n trombosis venosa.
La e f e c t i v i d a d d e 105 p r o c e s o s
siempre, depende d e el g r a d o d e descompensaci¿~nd e el
empleados,
f l u i d o sanguineo a r t e r i a l .
En t o d a l a e m b o l i z a c i a n a r t e r i a l y un
avance d e b i l
e n l a s enfermedades t r o m b o t i c a s ,
siempre,
esos
p r o c e s o s pueden n o ser a v i a b l e s ( v e r r e f . C ) .
Calor
directo;
E l c a l e n t a m i e n t o d i r e c t o d e miembros es el medio
l a temperatura mas
mas e f i c i e n t e d e v a s o d i l a t a c i o n e f e c t i v a ,
alta(opico)
de
los r e s u l t a d o s d e t e m p e r a t u r a l o c a l ,
e n un
i n c r e m e n t o d e a c t i v i d a d c e l u l a r con un aumento i n c i d e n t e en l a
concentracion
d e a c i d o s metabolicos e histamina
y
otras
substancias.
Esos a g e n t e s q u i m i c o s son potentes v a s o d i l a t a d o r e s ,
e n a d i c c i a n ( o suma) d e l p i c o d e l a s t e m p e r a t u r a s d e un
centro
medril armente
esti mu1 ado
por
sangre,
para
ejercer
una
vasodilatacion
refleja;
aumentando l a temperatura y f l u i d o
s a n g u i n e o e n un extremo por c a l e n t a m i e n t o d e alguna p a r t e remota
d e l c u e r p o y es basado e n e l p r i n c i p i o d e l a r e s p u e s t a r e f l e j a .
E l c a l o r d i r e c t o p u e d e ser a p l i c a d o por uso d e lamparae d e c a l o r
radiante,
c a l e n t a m i e n t o por conduccibn d e e l e c t r o d o s electrices,
b o t e l l a s d e a g u a c a l i e n t e y fomeritos,
c o n t r o l a d o r e s d e calor
termostaticamente y
l a c o n v e r s i o n d e calor
por
Diatermia y
Microondas.
E l e m p l e o s i e m p r e d e c a l o r l o c a l e n v u e l v e y asume 01
calcular
el p i c o ,
el c a l e n t a m i e n t o e f e c t i v o d e l a e x p o s i c i b n d e
t e j i d o s es e n t o d o el t i e m p o mas g r a n d e q u e el e f e c t o m e t a b o l i c o
asi
que,
sin
m o d e r a r n u n c a el c a l e n t a m i e n t o ,
esto es un gran
p e l i g r o d e quemadura,
manteniendose l a temperatura d e
1 i
s u p e r f i c i e b i e n con a p l i c a c i o n l o c a l d e c a l o r d e p e n d e d e l a
capacidad
absotiva
d e calor e n el
f l u i d o sanguine0
Sin
impedancia,
l a s enfermedades d e arterias o c l u i d a s e x c l u y e esta
funcibn
d e el
sistema vascular,
y l a
cantidad d e c a l o r
es
p e r m i t i d a p a r a a c u m u l a r s e en un p u n t o c r i t i c o e n l a d e s t r - u c c i b n
d e l o s t e j i d o s . En l a suma di2 una i n a d e c u a d a d i s p e r s i b n d e Calor,
el
concomi t a n t e d e
un
proceso metabolico local
puede
ser
deteriorado por
c o m p o s i c i o n d e los r e q u e r i m i e n t o s d e o x i g e n o
alrededor
d e los t e j i d o s anoxicos,
si b i e n es p o r
acumuldCibn
local d e productos y metabolitos .finales.
Calor Indirecto;
Esto es r e c i e n t e m e n t e l a h i p o t e r m i a g e n e r a l d e
el
cuerpo o “invernacion” a r t i f i c i a l ,
p u e d e g a n a r o b i e n merece
el
reconocimiento
en
este uso e n c i r a g i a c a r d i o v a s c u l a r
y
neurologica.
E s t e es l a mejor c o n d i c i o n d r a m a t i c a m e d i c a q u e n o
p u e d e ser e x p l o t a d a , e n una ,aguda o c l u s i o n a r t e r i a l l a a p l i c a c i b n
d e m e d i c i o n e s h i p o t e r m i c a s p u e d e ser l e i d a y
a p o y a d a en
las
ecuaciones basicas
d e 1 0 5 r e q u e r i m i e n t o s m e t a b o l i c o s d e io5
tejidos,
con
l a disminucib,n d e s a n g r e a d i c i o n a l
Practicamente
siempre,
e s t a c e r c a n i a t e : r a p e u t i c a n o p u e d e ser c l a r a m e n t e
d e f i n i d a y es d i g n o d e e s t u d i o mas . f u e r t e . E s t o es u n i v e r s a l m e n t e
mejor a c e p t a d a q u e l a a p l i c a c i d n de c a l o r e5 a n t i f i s i o l o g i c o y
p u e d e ser a d v e r t i v o .
1.a
r e f r i g e r a c i d n a c t u a l d e u n m i e m b r o p u e d e p r o v e e r y p u e d e ser
extremadamente usada
e n control d e s e g u r i d a d e n una s i t u a c i o n
d o n d e es i r r e v e r s i b l e y c a m b i o s i s q u m i c o s e x t e n s i v o s , p e r o
donde
otras
c o n s i d e r a c i o n e s m e d i c a 5 m i t i g a n otros
procedimientos
i n m e d i a t a m e n t e , el p a n o c a l i e n t e d e un m i e m b r o d i s t a l e n un p u n t o
d e a m p u t a c i b n c o n t e m p l a d a es u s u a l m e n t e s e g u i d a p o r i m p r o v i s a c i t m
r a p i d a d e el p a c i e n t e , s u b s e c u e n t e d e s i n t o m a s toxicos,
d e una
c a i d a d e t e m p e r a t u r a y a b a t i m i e n t o d e el d o l o r , el e n s a n c h a m i e n t o
distal
no e s t a a s o c i a d o c o n d i s t r i i r b i o s d e u n a h e r i d a b o r d e a d a d e
l a c a b e z a y p u e d e ser una i n f e r c i o n s e c u n d a r i a .
k..OS
e s t u d i o s d e h i p o t e r m i a e n el t r a t a m i e n t o d e t u m o r e s l o c a l e s
p u e d e e s t a b l e c e r q u e el f r i o . p u e d e ser e f e c t i v o e n l a d i s m i n u c i b n
d e un edema y e f u s s i o n y r e l i e v e con un pafio.
Estas r e s p u e s t a s
aparecen y
p u e d e n ser
u s a d a s e n el uso d e b o l s a 5 d e h i e l o
a p l i c a d o en
l a p a n t o r r i l l a y m u s l o p o r a l g u n o s f i s i c o s e n el
t r a t a m i e n t o d e p a c i e n t e s con t r o m b o f l e b i t i s y t r o m b o s i s venosa.
Inflamacidn,
indoracidn
(endurecimiento)
edema y a p a r e c e p a n o
que p u e d e ser c o n t r o l a d o r a p i d a m e n t e ,
a s i e l f r i o p a r e c e ser
mucho mas efecti.vo q u e los fomentos c a l i e n t e s ,
un
tratamiento
ocasional
e n p a c i e n t e s d en e s t a m a n e r a p u e d e 5er
el f r i o
intolerable asi
q u e su a p l i c a c i b n p u e d e ser t e r m i n a d a .
&si un
i n d i v i d u o s i e m p r e , e5 el u n i c o que m a n i f i e s t a 5u g r a d o i n u s u a l d e
v a s o e s p a s m o s e c u n d a r i o s q u e r e s p o n d e n mejor‘ a los b l o q u e s d e l
C. N S i mpat ic o
Temperaturas a l ternantes;
E l L L ~ Od e b a h o s d e a g u a c o n t r a s t a n t e s ,
e n el c u a l el p a c i e n t e es s u m e r g i d o a l t e r n a d a m e n t e si sus p i e s e n
,
.
.
24
el baho y agua f r i a ,
e s ahora empleado e n a v a n c e s pequeños d e en
el t r a t a m i e n t o d e enfermedades v a s c u l a r e s í v e r ref . A ) .
Con io5
problemas a r t e r i a l e s ,
por e-iemplo l a c o n s t r i c c i b n d e l a imersion
en
f r i o pesa mas que el supuesto e f e c t o b e n e f i c i o s o d e a l t e r a r
1 0 5 c a l i b r e s d e los vasos,
en los p a c i e n t e s a l e r q i c o s a l f r i o ,
siempre esto es a l g u n a s v e c e s b e n e f i c i o s o p a r a efectos g r a d u a l e s
d e s e n s i b i l i i a c i b n por t r a t a m i e n t o s d i a r i o s con imersion d e los
efectos e x t r emadamente d e n t r o d e l agua,
que es
progresivamente
enfriado(Ver
c a p i t u l o 29 y r e f ,
d e diagnostico radiologico).
CINALISIS
i
DE
TUMORES INTRACRANEALE6.-
Sumario.Un
analisis
de
145
tumores
,intracraneaieí
o b s e r v a d o s e n el
departamento d e p a t o l o g i a ,
Maulana MPdical
College y
a s o c i a d o con I r w i n g
ti.
R, H o s p i t a l . P a n t s fueron
sacados, . l a f r e c u e n c i a r e l a t i v a d e 1 0 5 d i f e r e n t e s tumores,
son
sitios,
l a edad y sexo d e 1135 p a c i e n t e s es r e p o r t a d a y comparada
con reportes p r e v i o s d e l a l i t e r a t u r a .
1 n t r o d u c c i o n . - Reportes ien el a n a l i s i s d e lesiones que ocupan
el e s p a c i o i n t r a c r a n i a l pueden ser d e s c r i t o s por d i f e r e n t e s
autores d e d,iferentes p a r t e r d e l a India.
En 1967 l a r e l a t i v a
i n c i d e n c i a d e l a s . l e s i o n e s que ocupan e l . e s p a c i o 11itraCranidl
fueron r e p o r t a d a s por R a t h c e t ,
a l l),
y Chandra
(et,al
2)
r e p o r t a n una r e l . a c i b n entre l a e d a d y sexo d e otros p a c i e n t e s y la
i n c i d e n c i a d e gliomas intracraneales.
En 1966 D a s t u r e I y e r ( 3 )
r e v i s a r o n 450 'lesiones qu'e ocupan, el
espacio lntracraniai.
Nosotr'oe
consideramos :un p r o f u n d o e s t u d i o d e
e n f er-medades
c l i n i c o p a t ~ d o g i c a sy lesiones n e o p l a s t i c a s . d e l c e r e b r o y r e p o r t a n
SLI p r e s e n c i a d e l a 5 d i f e r e n t e s p a r t e s d e l p a i s .
Material
y
Metodo.- E l m a t e r i a l comprendido d e especimenes
q u i r u r g i c o s r e c i b i d o s en el departamento d e p a t o l o g i a d e Maulana,
el estudio i n c l u y e 145 tumores i n t r a c r a n e a l e s c o l l e c i o n a d o s por
un p e r i o d o d e 5 ' a h o s d e
1970 a 1974,
los tumores fueron
c l a s i f i c a d o s d e a c o r d e a l a c l a s i f i c a c i o n d e Kernohan y Cagre.
R e s u l t a d o s . - E l numero t o t a l d e v a r i o s tumores i n t r a c r a n e a a l ~ s
y el r e l a t i v o p o r c e n t a j e e s dado en l a t a b l a 1 , l a edad y sexo d e
105
p a c i e n t e s y e l s i t i o d e esos ,tumores e s mostrado e n l a t a b l a
2,
i o 5 s u b t i p o s d e g l i o m a s , son una e v i d e n c i a r e l a t i v a y el X d e
edad d e l o s p a c i e n t e s es mostrado e n l a tab1.a 3.
Gliomas y
maningiomas c o n s t i t u y e n l a mayoria d e los tumores i n t r a c r a n e a l e s
( c e r c a d e l 77%).
A s t r o c i toma:
Constituye
78%
d e el
total
de
gliomas
intracraneales,
el p a c i e n t e mas j o v e n e n e s t a serie f u e d e cinco
ahos y m e d i o (hombre) y el mas v i e j o f u e d e 62 años (hombre),
la
mas a l t a i n c i d e n c i a o c u r r e e n p a c i e n t e s con edad e n t r e 30 y 40
ahos,
los hombres e n pr-oporcibn d e l a s mujeres f u e d e 1 . 6 : 1 ,
de
i o 5 62 tumores, 36 son d e g r a d o 1 y 2 y 26 son d e g r a d o 3 y 4.
Eperidi omas:
Constituye
el
12% d e t o d o s
105
gliomas
i n t r a c r a n e a l . e s , e l p a c i e n t e mas j o v e n f u e d e 3 ahos (hombre) y el
mas v i e j o Cue d e 35 años ( m u j e r ) .
E l 8% d e los p a c i e n t e s son d e
una edad entre 1 y 20 ahos, l a r e l a c i b n hombr-e-mujeres es d e 3 : 2 ,
ocho d e i o 5 d i e z tumores son i n f r a t e n t o r i a l e s y unicamente 2 son
supratentoriales,
microscopicamente 3 son e p i t e l i a l e s ,
uno u f e
p a p i l a r m e n t e y los r e s t a n t e s 6 son d e t i p o c e l u l a r .
Medulablastoma:
Estos son d o s c a s o s d e meduloblastoma en
25
. .
. .
,mujeres; u n o f u e d e 5 y o t r o d e 13 ahos,
ambos tumores fueron
l o c a l i z a d o s e n l a - . p a r t y e i z q u i e r d a d e l l b b u l o . d e el
cerebelo,
y
m i c r o s c o p i c a m e n t e son d e t i p o c l a s i c o .
Estos son d o s casos d e o l i g o n d e n d r o g l i a s
Oligodendrogliomas:.
(.3X d e l o s g l i o m a s i n t r a c r a n e a l e s ) , . ainbos p a c i e n t e s son hombres
d e , 22 y 36 ahos.Un tumor f u e l o c a l i z a d o e n el h e m i s f e r i o d e r e c h o
y
.ot,ro e n
el
lobulo
izquierdo
temporal,
cerebral
microscopicamnente, , una ant:imezcl'a d e a s t r o c i t o s n e o p l a s t i c 0 f u e
r e v e l a d a e n esa p a r t e .
.
Nerviogliomas:
Estos sori, d o s c a s o s d e n . e r v i o o p t i c o q 1 i o m a ; el
p a c i e n t e .fue d e 14 anos mujer y el 'otro f u e d e c i n c o afloe y medio
hombre,. Esto .fue , e n un taso d e el n e r v i o o l f a t o r i o g j i o m a en un
p a c ; i e n t e d e 2 ahok. homhre,
e n est.05 dog carjos l a p o s i b i l i d a d d e
a c t r o c i t o m a . . f u e c o n s i d p r a d a cm una examinacion m i c r o s c o p i c a .
Meni n g i &ma':
Forma el seyundo grupo mas g r a n d e de. neop1,asmas
intracraniaIek.,
c o n s t t . i t u y e n ..23.%d e el t o t a l . La edad r a n g o f u e
d e 9 a 65 amos,
l a ma5 a l ' t a i n c i d e n c i a o c u r r e , e n p a c i e n t e s d e
Microscopicamente,
4 son ~ 1 a s i f i ~ a d o s
edad entre 2 0 ' 9 . 3 0 aftos.
como f . i b r o c i t o s ,
5 como anyliomas,
4' d e esos muestr-an a r e a s d e
calci$i,cacibn.Esos
son
4 casos con s i g n o s c i t o l o g i c o s
do
m a l i g n i d a d y e v i d e n c i a d e i n , f i l t r a c i , b n e n el hueso.
Neuroma acusto:
Esos soin seix casos los cuales
(4%), todos
e s t á n v e l a c i o n a d a s con el oct.avo n e r v i o ,
el r a n g o d e edad f u e d e
24 a 45 aha's.
Desarrol1.0 d e tumoyes:
¡En este gritpo esta;' d o s cordomas,
un
cranifarygioma;
un c y s t e p i d e r m a l
y
3 colesteatomas.
Ambas
cordomns t i e n e n e v t e n s i b n supras.@lar, u'no o c u r - r i b e n un hombre d e .
45' a k o s . y el o t r o e n una mujer d e 50 ahos.
La c r a n > o f r a r y q i o m a
fue v i s t a
e n un h o m b r e d e 13 ahos;
esto f u e un tumor con. masa
c y s t i c . a a m a r i l l e n s e ( n i ' & a p e s c a d o ) s u p r a s e i a r , , e n l a c u a l f u e en
un a r e a d e c a l c . i f i c a c i ' b r t .
Esos 3 c o i e s t e a t o m a s fueron v i s t o s en
hombres entre 2 C i a 40 ahos ( p r o m e d i o d e 28 ahos) y t o d a s l a s
lesinnes supratentoriales.
Sarcoma:
Estos fueron 4 casos de.sarcoma,, u n o f u e e n r e t i c u l o
celular
mostrando. e v i d , e n c i a de. - e r o s i b n en el h u e s o ,
uno f u e un
f i b r o s a r c o m a , y l o s r e s t a n t e s . 2 fueron no c l a s i f i c a d o s .
Tumores F i t , u i t a r . i o s : Estos, fueron 5 adenomas p i t u i t a r i o s ( 3 % ) ,
m i c r o s c o p i c a m e n t e . 3 fueron adenomas cromofobe,
y
2 fueron
adenomas a c i d o f o l i c o c'on e v i d e n c i a d e acromegalia..
El
paciente
mas. j o v e n e n e s t a serie , f u e de 25..ahos y el ma5 v i e j o d e 38 ahos.
.Tumores M e t a s t . a t i c o s :
Eston son 6 casos,
en 2 d e esos el
tumor p r i m a r i o gue en 105 p u l m o n e s ,
en 2 e n l a b r a s t y 1 en el
estomago.
En i.1.n. caso fue mi.croscopicamente un adenocarcinoma, el
. s i t i o d e el tumor p r i m a r i o n o puede ser a c e r t a d o .
T ~ i m o r e sV a s o f o r m a t i v o s : , Estos son 5 casos,
2 d e los c u a l e s
son,hemangi ob1 astnmas .y 3 hemangiomas.
Discucibn;
En or-as series,
l a i n c i d e . n c i a d e g1,iomas f u e mas
a l t a que e n l 0 5 . o t r O s tumores i n t r a c k a n e a i e s .
~ s t o sf i n e s f u e r o n
tambien r e p o r t a d o s por o t r a s a u t o r e s ;
Grant ( 5 ) fundo d e ellos
que. 'el
48% d e l a 5 l'esiones qLie ocupan un e s p a c i o i n t r a c r a n e a l ,
s i n ' g r a n u l o m a s . En l a s e r i e . C h a n d r a , los g l i o m a s forman el 36% d e
t o d a s l a s lesiones que ocupan e s p a c i o i n t r a c r - a n e a l . La i n c i d e n c i a
es más b a j a que otros p o r que' n o i n c l u i m o s granulomas.
Zulch (6)
da un 45% d e tumores..i.ntracraneales, a s t r o c i t o m a f u e el m a comun
d e todos 1 0 c . g l i o m a s .
E l pc.r-centaje d e edad d e los p a c i e n t e s con
'
;. .
c
I
c
c
c
e
c
,
26
a s t r o c i t o m a e n o t r a s series .Fue d e 32 ahos.
En otras series f u e
s i e m p r e s i m i l a r a l a d e Dastur,
el ependiomas c o n s t i t u y e 12% d e
l o s g l i o m a s i n t r a c r a n e a l e s eri o t r a s series, como e5 comparada con
10% e n l a s e r i e d e Chandra. E 1 p o r c e n t a j e d e edad d e p a c i e n t e s en
otras s e r i e -fue d e 14 anos,
m i e n t r a s que e n l a serie Dastur
fue
un p o c o ma a l t a d e 18 anos.
Estos son 12 hombres y 7 mujeres en
otras
series
l a r a z o n 1:ue d e
1.7:l.
Meduloblastoma
y
oligondedrogloma
forman un pequeho p o r c e n t a j e d e c a s o s e n otras
series.
Meningiomas son l i s segunda mas f r e c u e n t e neoplasma
i n t r a c r a n e a l (23%), C h a k r a b a r t i , r-eporat como i n c i d e n c i a d e 14% y
Dastur d e 13% d e esos tumore!s e n lesiones i n t r a c r a n e a l e s e x c l u y e n
granulomas.
O l i v e r c r o n a da una i n c i d e n c i a que puede 5er 20%. L a s
l e c t u r a s e s t a t i c a s l a fr-ecurmcia con l a cual
o c u r r e meningioma
E:l promedio d e edad d e esto f u e d e 37
varia
considerablemente.
ahos.
En l a s e r i e Dastur fue d e 26 hombres y 18 m u j e r e s , p e r o e n
o t r a s ,fueron mas mujeres que hombres.
Neumonas
acusticos
( n e u r i l e m o n a s ) o c u r r e n en 4% d e l o s c a s o s e n o t r a s series. E l % d e
n e u r i l e m a s r e p o r t a d o por
I?ath(l)
y
D a s t u r ( 3 y B)
es a l t o 10 y 8% r e s p e c t i , ~ a m e n t e ) . Zimmerman(l0) r e p o r t a una
variacriar; i n c i d e n t e d e 27%, mientr-as Katsura funda que puede ser
como un 1 2 % .
Una comparable i n c i d e n c i a d e 5% fue r e p o r t a d a por
Grant
( 5 ) . E l promedio d e 'edad f u e d e 32 akos,
comparable con
üastur
f i g u r a d e 33 akos.
Tumores p i t u i t a r i o s ,
o c u r r e e n 3% d e
otros ca50.5, mientr-as en D a s t u r l a i n c i d e n c i a fue d e 8.7% y e n
C o u r v i l l e fue d e 3.4%.
E l promedio d e edad e n o t r a s series es d e
-7
4.2% m i e n t r a s que 105 p a c i e n t e s e n l a serie Dastur f u e a l t a
(38
akos.
D e s a r r o l l o d e tumores,
o c u r r e e n 5% d e otros casos,
como
comparacion
con un r e p o r t e i n c i d e n t e d e l a l i t e r a t u r a con
variacibn
d e 3% ( o l i v e r c r o n a 9) a
10% K a t s u r a í l l ) .
'Tumores
vasoformativos,
o c u r r e en 3% d e o t r o s c a s o s ;
el
promedio d e
e d a d e s d e otros p a c i e n t e s f u e d e 26 anos. Z u l c h ( 6 ) funda en e l l o
el
I % d e c a s o s y Dastur e n 5% e x c l u y e n d o c a s o s d e granulomas.
Sarcoma f u e l a mas b a j a i n c i d e n c i a en l a s series p r e s e n t a d a s
(3%);
fulch
(6)
r e p o r t a una i n c i d e n c i a de 3% y
Dastur
0.13%.
Tumores M e t , a s t a c i c o s , o c u r r e n e n 41.4% d e o t r a caso. E l i n c i d e n t e
reporte es 4% por Cushing (13), 4% por Z u l c h
í6),
4.1% por
n l i v e r c r o m a í9), 4.3% por t:atsur-a í l l ) ,
y 5.2% por Dastur
(B),
i n c l u y e n d o granulomas.
En o t r o e s t u d i o d e g l i o m a s , .,donde s i e m p r e
los tumores comunes y ,
s i e m p r e con menimgiomas,
c o n s t i t u y e n un
77% d e el numero t o t a l d e tumores i n t r a c r a n e a n o s ,
cuando mas
comunmente es el s i t u a d o s u p r a t e n t o r i a l m e n t e .
Los mas a f e c t a d o s
son los hombres despues que l a s m u j e r e s l a e x e p c i b n a l a r e g l a
dada e n casos d e meningioma y adenoma p i t u i t a r i o .
La i n c i d e n ' c i a
mas a l t a de lesiones m e t a b o l i c a s en mujeres no es s i g n i f i c a t i v a .
Como recordamos,
l a edad e n t r e 20 y 30 ahos es l a mar
afectada
c omun men t e.
~
27
P
33
23
4
3
3
4
wooma
e
3
3
TOTAL
ZOO
&4)
.2
2
3
L
c
c
c
-r
33
AI margen de la práctica
da%
El láser -un nuevo medio terapéutico
Nuevos experimentos y p r o g r e s o s
W.Schweisheirner
.. .
nEl láser en realidad se halla solamente al comienzo de la investipción clínica practica d e sus
posibilidades de empleo dentro de la medicina.))
Estas palabras optimistas proceden de L . Goldman.
director del Laser iabordtorium de la Universidad
de Cincinnati. y de R . J. Rockwell. fisico jefe de este
centro de investigación. Desde el descubrimiento de
la acción del laser. este instituto figura a la cabeza
en el c a m p de la aplicación práctica del láser en la
medicina. De vez en cuando se elevan voces en conma
de la aplicación de w e método de tratamiento. concretamente en la cirugia. Es d i p i i de consider;ir I:I
respuesta de estos dos investigadores al respecto:
((la verdadera labor de investigación del efecto liser
no
deniro de la cirugía se halla en sus coniienzos
está temiinando)).
Sus campos d e a p l i c a c i ó n en la m e d i c i n a
,
Por ahora el campo principal de la aplicación
práctica del laser en la medicina lo constituye la fijación de la retina desprendida dentro del ojo. Pero en
muchos otros campos de la terapeutica se experimenta
su efectividad, parcialmente con éxito: en la piel, en
los órganos interiores. en el cerebro. en la lucha
contra tumores malignos. Muchos puntos están en
estudio e incluso descubrimientos positivos requieren
niás confirmación clinica antes de poder contar
con ellos.
U íralutiiiwm
i ~ o t rIu.wr
a2 las Iwiiorrugias gasiricus
~
Las hemorragias de la mucosa gastnca pueden
detenerse en un intervalo de segundos con el trataniientn con un.gastroscopio laser. Tal es el resultado
de experimentos con animales, llevados a cabo por
P r o p i e d a d e s del láser
R. Goodale y otros en la Universidad de Minnesota.
El laser es un sucesor técnico del máser. El amó- 4 de los que informo en la asamblea de la (Central
niiiio LÁSER se ha formado de las leuas iniciales
Surgical Association» en Detroit. Este método actúa
de «Light Amplification hy Stimulated Emission o1
64 veces más deprisa que el restañamiento por elecR:idi:ition» (amplificación de la luz por estimulo de irocoa~ulación.y la perdida de sangre es mas reduI:] ciiiisión de radiacióiii. L a palxhra VÁSER es.
cida. Los experimentos se llevaron a caho en perros
ion
;i\iniirmo. u n acróninio dc «hlicr«uave Arnplific, I’
iinrcoti7:ddos. a los cuales se habn administrado
h! Stimulated Emission of Radiationn ~aiiiplific:iei6n hcparina para inhibir la coagulación sanguinea. En
dc las microondas por estimulo de la emisióri de un grupo de perros (A) se produjeron Úlceras gástncas
r:idiacíón).
prnfundas y profundamente sangrantes, de unos 3 cm
El Maser fue descubierto simultáneiimriitc eii lii- de diámetro. En otro grupo (B)se provocaron unihnr:itorios norteamericanos y TUSOL El primer miser camentc lesiones ligeras y superficiales de la mucosii.
norteamericano lo construyeron en 1954 los f i w o s
En los perros del grupo (A) pudo detenerse la h e m e ,
Gordon. Zeiger y Tounes. de la uniwrsidad neoyorrragia cinco segundos después de la aplicacion del
kina de Columbia. Unos seis años después. la Hushes laser. La pérdida de sangre se redujo a los dos minutos
Aircraft Company hahia Ilewdo a su plena aplica8:ión
del iratamicmo en el 84 :O. mientras con la electre
pi ictica el primer « m a w óptico». SI I k r .
coagulaci6n la pérdida de sangre sólo habia dismiLa tcnipera1ur.i cii el punto S i u l del rii)n de l a w nuido al who del mismo tiempo en el 54:‘:. En los
\c niidc en milhmes de Fados. Su cricrgi;: c’i cicii rxrros del grupo (B). con lesiones ligeras y supefiniillones de wcei mayor que la enerpi de I:I luz en cialt? de la mucosa gástrica. se logro asimismo mcla wpcrficie del sol. Para lograr xrnejante conden- diante el rayo del laser al cabo de cinco segundos
u c i d n de lucrza. w pro’rcta 1;1 luz de un I á m coil- la dcicnción de la sangre. Mediante la electrocoapu\ c . i i c i i > n a l a tritvcs de una serie dc Iciites. concentrini;iciUn Y* requieren unos cuatro minutos.
&de cii unii 5uperlicir dr un di;imetr,>dc media micrzi
De siete a diez días después del tratamiento w n
:.
Schweisheimer,
94
láser se mató a los perros y se investigó la mucosa
gastrica. En todos los casos se demostraron procesos de curación. Las exploraciones microscópicas
revelaron que el tratamiento con láser no habia producido lesiones en otros tejidos.
Estos resultados se corresponden con expenmentos anteriores de Goodale y Mullins. en los que se
logró, mediante el rayo laser una rápida detención
de la hemorragia despuk de una extirpación parcial
del higado o por una lesión hepática.
Lo uplicurión del /user m
oftulniulogiu
Ch. J. Campbell del College o f Physicians and
Surgeons de la Universidad de Columbia es u n o de
los primeros médicm que ha empleado el laser en
oftalmología. concretamente en los desprendimientos
de retina. fisuras retinales, angiomas y otros tumores. El y sus colaboradores. al cab0 de unos años
llegaron a la conclusión de que «la fotocoagulación
con láser promete convertirse en un valioso mét.odo
terapéutico. La técnica clinica correspondiente a este
método es sumamente sencilla y la reacción de los
pacientes excelente. Se han observado relativamente
pocas complicac~ones y, en general, no ban podido
comprobarse daños duraderos como consecuencia de
su aplicación)).
Campbell posee una experiencia especialmente
amplia en el campo del empleo del láser en la oftalmologia. Valora este método con gran confianza.
concretamente en lo que atanie al tratamiento del desprendimiento de retina. En el retinoblastoma considera indicada la fotocoagulación profilactica. Según
el. este método es aplicable también de un modo
satisfactorio en la periferia del ojo.
El tratamiento con un laser de rub¡ durante un
tiempo brevisimo (500 microsegundos) y a 6.943 Anpstrom en los pacientes Únicamente ha ocasionado dclores o sensaciones desagradables de poca importancia. No fue necesaria la aplicación de anestesia. En
el tratamiento del ojo con laser no puede mocerse
Io cabeza. Por io regular. el paciente se halla en decúbito sacro supino plano y el médico lo traía desde
arriba. Los pacientes con trastornos perifiricos del
ojo pueden recibir un tratamiento ambulatorio y. en
la mayoria de los casos. regresan a su l u p r de trabajo ai cabo de pocos dias.
Otra valiosa roma de aplicación del láser la constituye el tratamiento de la retinopatia diabética. incluyendo concretamente las hemorragias retinales
dentro de un cuadro de diabetes. L'Esperance. del
Centro Médico Presbiteriano de Columbia. en Nueva York. ha informado del tratamiento con Iásar de
250 pacientes. la mitad de los cuales padecia de retinopatia diabética. El tratamiento con láser procura
la obturación de los diminutos aneurismas que se
desarrollan en los vasos de la retina en la diabetes
;i\arvada: de este modo se intentan impedir las hemorragias de la retina.
*
El
Iuser
L'Esperance utiliza en su tratamiento el denominado láser verde y no el laser de rubí o el arco de
xenón. Considera importantes en este punto dos particularidades técnicas. Por un lado, gran pane del
rayo rojo del laser de ruhi es reflejado por los vasos
saiipineos de la retina, ya que éstos contienen la
roja oxihemoglobina. En cambio, el láser verde de
ar_eón Iopra la absorción del 75 de su luz verde.
de una longitud de onda de unos 5000 Angstrom.
por parte de los pequeños vasos sanguineos retinales.
Ademas, con el laser de argon es posible una punieria especialniente precisa y su reducido número de
vatios ocasiona una quemadura de menor consideración.
En el tratamiento con el laser verde, además de
las retinopatias diabéticas. se han incluido también
tumores superiiciales. coroiditis y lesiones en el ojo
anterior. y está previsto el tratamiento con láser de
la fibroplasia retrolental.
En los dos últimos años, en Boston se han tratado
329 pacientes de retinopatia diabética de distintogrado
con la fotocoagulación con rubi (Escuela Médica de
HarGard. Joslin Diabetes Foundation y el Hospital
de Diaconisas de Nueva Inglaterra). Los autores
Beetham, h e l l o , Balodimos y Koncz (Arch. Ophthal.
marzo 1970) califican sus experiencias con la laseroterapia en estos casos como «estimulantes y efectivas).
En estos pacientes habia una retinopatia diabética igual en ambos ojos. Sólo se trató uno de ellos.
sirviendo de control el otro ojo. El 80 % de los ojos
tratados con láser presentaron una mejoria clara, y
desaparsieron totalmente los fenóm&os retinopiticos en el 54 "4. En cambio. todos los ojos no tratados siguieron igual o empeoraron durante el periodo
de exploración.
Camphell aconseja iniciar el tratamiento con pequeñas dosis de láser y aumentarlas si es necesario
paulatinamente. Para lograr el nivel de láser adecuado se consideran necesarias. por io general, dos correcciones del ajuste inicial.
- El
lusm
et1
el
rruruniimto
del &mer
L. Goldman. precursor en el campo de la investigación biomédica con el láser, ha investiga& criticamente el tratamiento con láser practicado hasta
ahora en los tumores malignos. Considera que o h cen perspectivas favorables aquellos casos en que el
tumor es de fácil acceso y no responde a un trata- '
miento con los medios convencionales. €3tratamiento
quirúrgico de las enfermedades cancerosas ha llegado.
según el, a una «meseta», y el cirujano vuelve sus
ojos en busca de ayuda hacia el ingeniero y el fisico.
para lograr nuevos avances.
Aunque no se dispone de material suliciente para
una valoración definitiva. el tratamiento del cáncer
y de otros tumores malignos, con láser prosigue
con interés y muchas esperanzas. 'P. E. McGuíí.
director de la Fundacion para la Investigación Mi-
,
Schnrislieimer.
El
/&ur
~
Efecto del láser sobre bs vasos sanguíneos
dica con láser en Boston; Massachusetts; observó un
.
~erecto favorable en el traiamiento-de-mefanumas~onYahr. Strully y Hunvitt, del hospital neoyorkino
láser. Llegó a la conclusión de que «el láser conlitituye
de.Montefiore, investigaron el efecto del-láser en las
~.
una forma de enefgia-ünican: -En oíros informes
arterias de perros en los que habian provocado preMcGuii fue más reservado y critico. Solamente conviamente alteracionq~arleri~oscl-eroti-s,___.,_~
~. .
.
sidera logrado el éxito de una terapéutica de #cáncer
Se emplean diferentes técnicas quirúrgicas para
cuando se ha destruido la última célula cancerosa y
anastonmar 10s~vasos.sanguíneos. E n r o d i i s e l l a s s e .
_~
la enfermedad no resuige con-los aiibs. Es iodavia
~produce. por lo menos. U M corta interrupción &h.
demasiado pronto para pronunciar un juicio definido
circulación sanguinea ; esta interrupción podría ocasobre la terapéutica con láser.
de los .. ..sionar. en ciertas circunstancias,~~una~~amenaza
Son interesantes los experimentos del neurociruórganos de importancia vital.
j a n 0 neoyorkino Stanley en el iratamiento de tumoEl nuevo metodo con láser evita una interrupción
res cerebrales con el laser de ácido carbónico. Halló
de ese tipo. Los experimentos se efectuaron con un
que el rayo continuo de este tipo de láser evita el
láser de neodimio en la arteria carótida. Para ello
efecto del shock. que se ha descrito con la aplicase prccede en cuatro etapas:
ción de los láser de rubi «pulsados». La acción del
I . ” Debajo del punto del vaso en que se encuenláser de ácido carbónico vaporiza y desintegra iotaltran
las inclusiones anerioscleróticas. es decir. en el’.. V:
mente el tejido canceroso. De este modo se reduce
lugar en que está proyectada la anastomosis, se deconsiderablemente la transmisión de células canceroposita una gota de sulfato de cobre. Mediante l a
sas del tumor tratado al tejido sano circundante.
absorción de esta.solución se influyen favorablemente
Según Stellar. el tratamiento con láser constituye el
las propiedades del tejido a la acción del láser.
mejor metodo para la extirpación de tumores de di2.” La arteria que debe servir para derivar la re
ficil acceso que se sustraen al tratamienio por sucgión arteriosclerótica convertida en intransitable dención o congelación.
tro de la arteria receptora, se ((pegan con un adhesivo
El ra?o laser conw «bivruri de luz» quirúrgico
quirúrgico al punto coloreado de la arteria enferma.
L a s dos arterias tienen entonces una pared común.
Una investigación en perros acerca del efecto de
3.” Se dirige el laser de neodimio contra el punla irradiación infrarroja con laser (c~ontinuouswave)).
to
coloreado
de la pared arterial. Con ello se produCWI de la piel. musculatura. cráneo. cerebro, higado
ce un agujero liso en l a pared común.
e intestino delgado. la realizo J.L.Fox. del Depar4.” L a consecuencia es que tras la formación de
tamento de Neurocirugia del Veierans Administrala
anastomosis.
la sangre de la arteria donante fluye
tion Hospital de Washington. Una fuerza eléctrica
libremente hacia la parte distal de la arteria receptora.
de unos 30 vatios, dirigida a un punto de la piel de
2 mm de diámetro. corta fácilmente la piel y la muscu- sin que haya que interrumpir la circulación sanguínea.
Los autores insisten en que sólo podrán sacarse
latura sin’ ocasionar una hemorragia considerable.
conclusiones
definitivas del resultado de -te metoCuando se produjeron hemorragias de mayor irnpordo
cuando
se
disponga de muchos más experimentos
tancia. impidieron la penetración del rayo de láser
Confian
que
este
método sea practicable también
~ en
~
... . ~ .
a través del cerebro y el higado. La energia del laser
el
hombre
y
están
convencidos
de
que
puede
llevarse
era absorbida en estos casos por la sangre y no fue
a la práctica.
posible una penetración más profunda.
__
~
~~
~~
~
~
~~
L a curación de las heridas cuianeas abdominales
tras irradiación con laser se retrasó en un principio.
pero iuvo un curso rapid0 después del décimo dia.
Experimentos comyiarativos entre heridas quirúrgic i s de bisturi y heridas producidas por láser no permitieron comprobar (ni aún con la microscopiii) diferencia alguna de consideración.
En el empleo del «exalpelo de IUD) Fox pudo
comprobar dos dificultades. I _‘I. cuando un ayudante.
inioluntariamente. tropezaba con.el brazo del cirujano. se alteraba la dirección del rayo de láser y se
produck un efecto imprevisto sobre el animal operirdo. el cirujano o sus ayudantes; 2.”. no podia haber
~rapiismetálicas u otros instrumentos quirúrgic<w en
el campo de operdción. porque reflejan la energia
1á5n contra el cirujano o sus ayudantes. Fox se
qucmd IJ mano dos \erns de este modo. Sin embargo.
la\ qiiem~iduras Silnilron r5pidamente
sin complic.+iiimt>>.
El rraruniieriro con laser de la piel
Se han tratado con laser una serie de trastornos
cutáneos de naturaleza no maligna. Los autores que
han informado de ello han visto éxitos en general
y opinan que este tratamiento debena practicarse en
mayor escala.
Este tipo de tratamiento ha demostrado ser muy’
electivo para eliminar tatuajes de la piel. Esto se relaciona con la acción especifica del láser sobre los
componentes pigmentarios de la piel. La piel normal
no resulu dañada con este metodo. Se han tratado
de un modo favorable alteraciones cutáneas de coloración intensa (nevus vasculares) y angiomas superficiales. Tambikn ha dado ya buenos resultados
esta terapéutica en las alteraciones pigmenurias menores. En el tratamiento de estus casos con Iáscr no
se requiere ni narcosis general ni anestzsia liral.
Schweishnmer. El lúwi
Se ha dudado de si el tratamiento con láser estará
indicado en alteraciones cutáneas de esle tipo. Frente
a estas dudas, Goldman y Rockwell. con su gran
experiencia, abogan por dicho método. Dicen: <<¿Qué
puede hacerse para tratar esos nevus vasculares incperables. incurables. deformadores. que alcanzan incluso a los párpados? A muchos pacientes les ha ayudado considerablemente el tratamiento con láser y no
hay que olvidar que el instrumental láser de que se
dispone hasta ahora es aún bastanie primitivo. Y
esto se refiere muy especialmente a los pacientes con
alteraciones dérmicas como los nevus \,asculara,.
Traraiviento con laser de los órgmos ittrerrlos
Existen numerosos estudios acerca del efecto del
láser en los órganos internos de animales, concretamente en el hígado. Pero el tratamiento con IRser
de los órganos internos del hombre se halla aún en
experimentación. Una rama de esta investigacior, st
dedica a ver cómo puede llevarse a cabo la extirpación de partes de órganos internos mediante la acción del Iáser. También se investiga la posibilidad
de emplear el láser en las operaciones de trasplante
de órganos.
La irradiación con láser de partes del cerebro es
de una efectividad especial cuando se ha levantado
la cubierta del cráneo de modo que el laser pueda
actuar directamente sobre el cerebro. Las experiencias clinicas obtenidas hasia ahora en este campo sc
considera n «esperanzad oras». Jus tiiican la organizi
cion de un programa intensivo para desarrollar las
técnicas más idóneas.
~
Medidas de prscauciOn en el tratamiento
con láser
Es coniprensible que una fuente de energia tan
«indómita» como los láser deba dominarse muy concretamente para que no Ocurran desgracias. La preocupación principal reside en que la exposición de los
ojos sin las correspondientes medidas de precaución
--aun cuando se trate únicamente de fracciones de
segundo- puede provocar la ceguera y quemaduras
irreversibles de la retina o de la lente u-ular.
Para proteger a las personas que trabajan con
láser se requieren sistemas de seguridad que den señales de alcirrna cuando se hace un uso excesivo del
aparato. Se recomiendan unas gafas de un espesos
de 4.3 cm. con un vidrio eslándar verdeazulado )
una densidad óptica del 10. Pero por si solas no bastan. En varios estados de Norieamérica. la legislacion ordena ya el registro y regulación de todos los
sistemas de láser.
Es especialmente p n d e el peligro cuando los
dectos del laser tienen lugar ai aire libre. En rela-
ción con investigaciones
llevadas a cab0 por el ejército de los EE.UU.. ha afirmado M.E. Lasser: «Un
observador que mirase directamente el rayo de nuestro «telémetro». correría peligro de sufrir quemaduras de la retina. aunque la distancia entre él y el laser
luese hasta de 18 kmw.
De un informe de la Western Electric Co. en BufFalo. N.Y.. EE.UU. se deduce que la aplicación de
láser. observando las prescripciones de seguridad.
puede llevarse a cabo sin daño para la salud. Emplean
allí los láser para tratar brillantes. de cuatro a cinco
horas al dia. No se ha observado ningitn daño en
materia de salud. Es cierto que el operador no trabaja
en la habitación en que se ejerce el efecto, del láser
sino fuera de ella y con ayuda de una pantalla de
\
televisión.
Conferencia Anual de Seguridad de
los Laser
E1año pasado tuvo lugar por tercera vez la asam-
blea anual de la «International Laser Safety Confe-
rence». que debe su existencia esencialmente a Goldman. En la asamblea de 1970 se comprobó el siguiente
e importante hecho: «Las deliberaciones acerca del
trabajo con laser han confirmado la idea de que el
peligro principal de lesión por acción de los laser
amenaza a los ojos. Cuando la fuerza de las radiaciones se mantiene por debajo de los limites que pueden constituir un peligro para la vista. se hallan fuera
de peligro los demas tejidos y órganos del cuerpo)).
En estas asambleas de seguridad se comentan y
discuten los factores de seguridad generales y especiales. encargados de proteger de lesiones tanto a los
pacientes como a las personas que utilizan el laser. Se
trata de u n asunto de importancia primord?al,
Probablemente no carece de justificación el que
un repíesentante de la Sociedad Médica de Nueva
York exteriorice sus dudas acerca de la extrema peligrosidad del efecto láser. Añade que: «Los verdaderos daños de tipo sanitario producidos por el láser
pueden ser mucho menorm de lo que hacen suponer
las advertencias de una serie de médicos. Pero. sea
como sea. no podemos dejar que siga adelante este
asunto, mientras no tengamos conocimientos sólidos
acercx de su efecto y de sus daños».
La Medicina curativa así como la preventiva lievan el camino de lograr estos conocimientos sólidos.
Hay que crear una nueva ierapéutica. Existe la esperanza de lograr con su ayuda éxitos terapéuticos
inaccesibles hasta ahora a la Medicina.
a
O
c
O
c
c
i
O
5
E'
5
F
F
o
cI
h
n
blood f l o w s
t
A A
M,=12.4
&
r-
M.iO.12
48.
T.
head
E" = 0.8*9%
33.37%
U
trunk
_*
basal: i m = 35 Vhr, is=12 I/hr
Fig. 19.4.
Diagram giving for all compartmcnt~resting sfrtc vulues of mrlabolic h i i i production (,W<,hheat-transfer ~oelticicnlsbetween <Om-
PPrtmmU (~csilionbetween units in the right hall of the ñgurei hsai-transfer co6Hicisnls bciwcen skin scyisntr and snvironmenl la1 lempsi'iure
TALand iníenriblc svrporative heat l o s ( E v ,marked by outward arrows) Mel~bolic
heat productionand evaporatiYS h a t Imarc in kcitlihr. transfer
sufficicnu in kcal/hr
Perentap listed together with bod E,, is the fraction. assigned to thc pnisvlar skin portion, of the 1Qal additional E,
brought into action when exheat must te lost by evaporation of sweat. The ien half of the figurn shorn the distribution ofblwd Rows. The brain
is p u l 4 81 40, the COR of the trunk at 210 litcr/hr. AU otha Rows may change according to demand. Their fractions of m u d e (1.) and skin blood
'a.
$
Row(i,).wcsruumcdta t e c o n ~ t a n u a n d a ~ l i ~ t c d ~ ~ t i n g v n l u ~ o f i , a n d i . . a r c g i v e n . T h e l i i i k a r r o i r j l o t h s c o r rhead.thcmuaslaofths
olihe
trunk, and the core ofthe exlremitis indicae that extra heat inpus wcur in shivering and in exercise. Furthermore. in SICIC~Y, it is assumed that 584
dtbtotal heat originatesin ikcorrolthscarcniitiaaFd38./in ibcmus~laofthctrunk.(Cl.eqs.19.~l9.13.)Thssiorapeapcilyofthccomprtmmu cin easily bc ~omputedfrom their ma(y.Fig. 19.3) rind C,, (d.
4. 19.11. After Sioiwijk and Hardy 119.11.
,,,,.
.
.. .
- .,-...,...,..,,
.. -,..,”.,.
----.,...
c
4
910.
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,
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s x
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.--
CHAPTER 3
PRINCIPLES OF PHYSICAL MEDICINE
m This chapter describes the therapeutic and
diagnostic application of physical energies in
rehabilitation medicine. I t includes thermotherapy (heat and cold), ultraviolefi rays,
electrotherapy,
massage,
manipulation,
stretching, and traction.
HEAT
Biologic processes generate and arc affected
by physical energies, one of which is heat.
It is the most commonly wed modality in
rehabilitation medicine and usually is applied
before exercises, stretching, or electrotherapy.
It is employed for both acute and chronic
disorders, and the physiologic effects are the
same whatever the source, varying only in
the depth of penetration.
Physics'
Heat is a part of the electromagnetic spectrum and is a state of particle excitation (entropy). Every atom or molecule above zero
degrees Kelvin has excitation and is capable
of transmitting energy to another particle
either by direct collision or radiation. Energy
transfer by collision in solids is conduction
and in liquids or gases convection. It only occurs when the absorbing particle has lower
entropy (temperature). Heat can therefore
only he transmitted from higher temperature
to lower temperature. Radiarion is the emission of photons (quanta or packets of energy'. which cross space and when absorbed
ran ( i ) increase the particle's excitation
state, (2) alter its chemistry, or ( 3 ) be reemitted as heat or light (fluoresrence. phosphorescence ' .
The skin is a g o d reflector. fair radiator,
and poor ronductor of heat. The absorbed
heat immediately encounters tlie high con-
.
centration of water molecules in the subcutaneous capillary and fat beds, which are
subject to physical and physiologic reactions.
The specific heat, the calories gain or loss
needed to change the temperature of a ,Tam
of a substance, is approximately threefold
greater for water than it is for other tissue
molecules. The subcutaneous water thus beromes an excellent heat storage reservoir or
insulator and significantly contributes toward
maintenance of relatively constant body
temperature.
Heat can also be produced in tissue by converting high-frequency electromagnetic waves
into (1) microcurrents (short wave or microwave) or (2) shearing, vibrational, frictional.
or compressive mechanical waves ( C . S . ) .
These are described as diathermy or "deep
heat" modalities and may penetrate to
muscle. Condurtive. ronwrtive or radiant
heat penetrates 1 to 5 mm and is rallrd
"superiicial" heat.
In summary, heat is electromagnetic energy, which is absorbed by a particle having a
lower temperature than a source. The absorbed energy will ( I ) raise temperature,
( 2 ) produce chemical reactions, (3) transmit
its energy to another particle, or (4) reemit
itself as light or heat.
The skin may reflect or absorb the energy,
and this last is achieved to the greatest extent
by water in the subcutaneous fat and rapillary beds.
Physiologic effects of heat'.'
Physiologic functions are governed by the
eneri? manipulations of spPrialiied niolerules. usually protein. in the reil, its iiiembranes. and extrarellular roinpartiiients.
These inolrcules have inherent mechaniral.
75
76
Rekabilitation
medicine
electrical, and chemical energy that they generate and trarkfer. Adding thermal energy LU
this system will increase these transduction
processes. Thermal energy in the water molecules of the aqueous solvent acts as a driving
force for these reactions and may increaie
oscillating motion, charges or dipole separation, or produce electrical changes. Additionally, hydrogen bonds may be made or broken,
and chemical ihanges result from alterations
in atomic and molecular configurations.
These effects are metabolic or catalytic and
function in life as the required substrate
molecules are available.
We may then @astulate the following .9cquence resulting írom the application of heat
to cells: ( 1) incrvase cellular catalysis-metabolism requiring ( 2 ) energy molecules (O2,
proteins, carbohydrates) producing (3) vasodilation and increased capillary pressures with
( 4 ) transudation and from alteration of
membrane configuration or dynamics (5)
ionic "pumping" of electrolytes and íiuids.
Continuing application or reduction of
temperature may result in ( I ) protein degradation creating histamine-like substances.
( 2 ' leukocytosis, and ( 3 ) concomitant inflammatory or anti-inflammatory reactions.
The molecular and structural characteristics of proteins such as connective tissue collagen are temperature dependent and elongate with temperature elevation.s- The
chemical energy of dephosphorylization of
A T P to ADP, with accompanying mechanical
work of shortening muscle fibers, generates
heat that may produce changes in the helical
configuration of fiber proteins, possibly on the
mechanical characteristics of the sliding filaments. Protein fractions such as histamina or
antigens (cryoplobulins) may be released
with temperature alterations. Membrane dynamics fluids and electrolyte are temperature
dependent, particularly those of excitable tissues such as nerve. Theoretically, these are
conformational changes in the membranes
that pervert thr seleitive ionic movement
(pumps). The niechanisms of impulse transmission including ionir. electriral, thermal,
and light enerpies are correlated. Infrared
emissions from live crab nerves have been de-
scribed.' The configuratio ):i of protei
molecules in end-organ mwnbranes, r 1,:
by environmental temper.!ture chani;
secretions such as synoviil fluids: I I
with tempaature elevatioil
In summary, thermal mergy atfe:.
structural and chemical characteri! t i
molecules, enzyme activity. degradatio:i
ucts, and membrane funcilon dong .
at the end-plate and seci ,.tory surfa:.(
I
I
' ,
' :'I5
,
i
.!
Clinical eñects of heat
Skin reaction locally d u d e s sei:
warmth, vasodilation (ery!huna), SWI:
reduction in skin mistanc.,, and incns.
l a a l tissue metabolism. It heating i r
tinued beymd 40 to 60 n.in, core t e r n
tun may be elevated and homeosta:i,
sponses of distal vaaodilatiiin occur.
Usually temperature, p l s q and t
pressure are unaffected, as are the ren 31
gastrointestinal systems. h'erve cond ti'
velocities and action potentials may ini.r
Muscle tone or tension m.iy soften, 1 1 1
elastiiity increase. Ligameiit and ca:r I
fibers may similarly gain ei;tsticity, ami
tion of joints increase. P a i n will occasiii ,
be relieved by heat. The exlilanation is 11
bly related to spindle gamm.i afferent rvIi
hut as yet this is not a satisfactory exld
tion. The anti-inflammatory action of
inclwdes leukocytosis, increased cay il
pressure, and humoral enzyme effects,
acting toward suppmion of the tissue 11 ,
tion.
The amount, rate, and direction of
heat gain or loss is dependent on the fcll
ing:
1. Source, its temperature artd duration < , I
p I i c at i o
2. The optical properties of the skin
3. Con-skin tempeiaturc grslicnt, which i a
from 5' to IO" C depending on the I
tested: Core temperature a\erager 37' t.,
C : skin 29" to 35' C
4. The amount of water ml far in the 5
cutaneous capillary and {al beds
5. Hypothalmic and skin ncuial ~ o n t r o l ~
, r .i
prui-id? mechanisms mniiitaining COISI
temperature, such u retie>: vasomotor re
"
, .
lions d i d to treated areas
6. Respiratory i n d excretor) mechanism i
~
:
I
I:
I:
~
I
.
.
I
Principles of physical medicine
7. Ambient temperature and humidity
(aged and infants tolerntc h u t pooriy),
B. Age
sex,
nutrition, exercise, hydration, sensitivity,
and diseq.
Indications
Heat is indicated for its ondgeric effect
primarily. The usual applications are for
musculoskeletal, neuromuscular disorden
such as neuralgias, sprains, strains, articular
problems, muscle spasms, trigger points, and
the host of terms that attempt to describe the
vague problem of muscle pain. Simons’ in an
exhaustive review of muscle pain syndromes
attempted to define the many tums used to
describe the problem and reported the pathologic conditions found by a few investigators. There does not appear to be a clear
description of the etiology, pathology, or
treatment, but heat and cold are recommended among many other modalities. The
cause of pain is obscure in the absence of any
defined pain end-organs in muscle. The antiinflammatory effects of heat were described
above.
Spasm of muscle is an indication for heat
treatment. The nature of this condition is included in Simons’ discussion but escapes definition. That it is benefitted by heat is often
noted subjectively and objectively.
I f possible, however, a diagnosis should be
made and aspirin or other anti-inflammatory
analgesic prexribed, with rest or splinting,
before embarking on a program of themotherapy. i
Heat before exercises, stretching, traction,
or mani$ulation, often enhances the effects
and benetits of these measures.
The use of heat in obliterative arterial or
in arteriolar disease is empinc and should
be employed with the greatest d e g m of caution.
Wounds and ulcen may be benefitted by
topical heat. Cellulitis and abscesses may be
ripened to the point of drainage with hot wet
rompresses. Open wounds. as heat may have
an evaporative drying and vasodilating effect.
niay be bmefitted.
Tlie soporitic effect of heat is achnowledged clinically. Its explanation is obscure,
hut empirically it provides benefit to many
’
77
patients. Providing this support in a department of rehabilitation medicine should be
done cautiously to avoid possible dependency.
The simplest modality that may be used at
home is often as effective as “sophisticated”
apparatus and has the advantage of being
easily employed by the patient or his family.
Contraindications
Heat, whatever its source, should not be
u d in acute inflammation or trauma until
the initial reaction has subsided, nor in venous obstruction, arterial insufficiency or
ischemia, hemorrhagic diathesis, or coagulation defects. In the absence of sensation
special care must be exercised.
In the presence of cardiovascular, respiratory, or renal failure heat should be used
sparingly, if at all. Active inflammatory arthritis particularly with joint swelling, may be
worsened subjectively and objectively with
the application of heat.
T h e use of heat over areas of solid malignanc) is contraindicated, although the possibility of either superficial or deep heat’s affecting a tumor‘s temperature may be questioned.
Sources
Conductive heating’
Conductive heating is achieved by direct
contact with the skin. T h e sources may be
( I ) solids-electric pad, hot water bottle,
sand peloids (muds), and poultices; (2)
liquids-water, paraffin wax, or compresses;
( 3 ) gases-dry or moist air.
The choice is one of convenience and
should include accessibility of the part, need
for movement, availability of the agent, and
the patient’s and physician’s preference. The
agents most commonly used in rehabilitation
are water, hot packs, paraffin, and moist air.
Hot water bottle, heating pad, moist packs,
and tub baths are available at home, making
these a preferred heat source.
Liquids.” Its accessibility, buoyancy, and
ease of temperature control make hydrotherapy a readily employed heat source. Normal heat loss with ,hydrotherapy niay be re-
70 Rehabiiit,ation medidin.
i
duced and u~~desirable
te@peraturc e k t h
.
&chr The tub, p o l ,
OCN.
'p,
.
w#th adeqwate hydration. Patients with diffuse musculoskeletal pain may be cmdidaies
for this treatment, but a hot tub or shower
at home would be equally effective.
and whirhi01
are used for palliation (yhulpod), a
r
u
C
e
,
or debndcment (wounds, uicen) .soapq, M6Radiant heot"
scptics, and deterguru & be added to the
RadiPnt heat is infrared radiation, which
water as appropriate buq often am unnccshas
a wavelength of.7X) to 12,000 nm and is
--safy=-~ul~body immersi& in tubs or tanks
above
the visible spectrum (390 to :'70 nm).
for reant widespread sJrface burns is us&
Its depth of penetration is approxiniateiy i o
in many centers. The a@dition of camman
.to 1 mm b r near (770 to 1500 n m ) , and I
salt at the ratio of 0.7 pounds per 10 gallons
to 0.05 mn for far (1500 to 12,000 nm).
of water bring.l the bath, to isotonic Oonanphotons at longer wavckngth have less entration, and maintcnancd of the tcmpCntUte
ergy, thedore. leu penetrability (Table 3-1).
with that of the blood b mommendcd.
The phriologic effects of radiant heat are
Pool t-mpraturc for exereire thm"
identical m those of conductive heat.
should be approximately '32O C (90' m 106"
Sources of radiant h u t are (1) luminous
F). Therapy prior to UJcrciSeS or stntchiag
or visible .infrared bulbs, which emit near
soft tissue injuries or woQnds should k da¡&,
infrared, and (2) noniuminous :-adiators,
starting at 10 to 15 mid and increasing Up
+ch
are metallic coih or wire cov~mdwith
to 20 to 30 rnin and on alternate days fbr
mfractory materials, which emit far infrared.
elderly or debilitated patients at appmxiThere may be some visible light in the coils,
matcly the same temperaturn.
and usuaiiy so with bulbs. Bulbs lor home
Compmc~a.These r n i y be turkish towYI,
iue are available, but caution must be exerstrips of felt or wool blhkets, or the si1ic;yte
c
i s 4 against the possibility of bums or Fm.
gel pack (Hydrocollator). The latter mains
heat longer when heat4 to 150° F and iras
OlATHERmY AND ULSRASOUND"
a temperature of 122O F 30 min after yPhysics
plication. Patients and fimilies can easily be
High-frequency currents are generated by
taught to UK packs at home.
m
oscillator that in addition to íi current
Panfñn wax. Paraffin. m i n a liqukl after
melting at a temperahin; of 120° F, and 4- source r q u i i a a capacitor-or condmscr and
an inductance coil. Modifications iipon this
ing mineral oil lowcn +e melting tanpesature. It i
rapplied dvecqy to the skin, and:& bksic circuit can produce electrcmagnctic
(radio) waves that have frequcncia deoften prescribed for arthritis of the hand or
fmt. The adherent oil ;Ind wax after its n- scribed as short and ultrashort (microwave)
compared to long radio waver. The lame
moval makes subsequent massage and ttretchbasic generator coupled to a piemelecmic
ing easier. I t s eñectiveness in acute swollen
crystal (transducer) is used in ultrasound
joint is questionable. E l q r i c heaters or d a i therapy.
hle boilers are available for home w.PaThe radio wave, when emitted from the
tients using this at home should have a thernioineier available to ensure proper tanpenaTable 3-1. Various ranges of the
tures.
electromagnetic spectrum
Heoting cobinets. Heating cabinets deliver
dry or moist heat and have varying acceptRange of
ance. Their siee. cost. and maintenance limit
Trpr of rodidon
wauclrngihr (nm)
their use. Exlming larga surface areas to an
Lons-wivc infrared
1?,000-1,500
environmental temperatjre higher than that
1,500. 770
Short-wave infnrcd
of the body and adding fnoisture to eliminan
Visible
770. 390
Ncl. uloivioici
3 9 0 290
evaporation will raia M y temperature. PmFar ultrrviolct
290. 180
found sweating should be compensated €or
mr-illatc3 .'I
a "Iield' t ' ,
the i:ou:~If'
ancc coil.
A. piiiio'
pacitor p l ~
and c o ~ ~ t r i
q c l e.
F'lacii g
tor plat 5
indJctaiici:
roiled c r
7 . 5 1 uevel
13.56. z7.1
'8
\v3<;e5a re
of 2450 cp
3Iicniw;i
scribed 8s Y
diainetcrs
inches, a r f
are coiinei
to [lie osci
The :eii
mii.mcr IT,:
bui similai
a \diirie
inilwda ic'?
im
fields
Diutheimy
The cui
field vary
tamce let1
the pla ;a,
plied. Un[
rcdUce<l, I
rent withi
KO ins:ru
current. h
t l w ''re io11
qriirrator
ill!: fiP1 is
durtan<.e
h l !
eIri:c1
3 t
ai
1:inip. ,in,:
'1-lie heat
rii;itely
\r;ives"
di1crt"'S
tliry
heat.
r
i
i
!
i
!
I
Princifirs of phy&al medicine 79
o~illator's antennii, seis up +uoeurrents in
a "field'' that dewdopr b e 4 n the plates Of
the coupled capacitor or within an inductance coil.
A pieroei&uic crystal pia+ between .a+tor
plates will subject it to expansions
and contractions with each oscillating half
cycle.
Placing a patient between coupled capaaitor plates will produce capachor heating, or
inductance heating where a ;wire is either
coiled or laid .on a part. T h e short (22, I I ,
7.5) wavelengths are k e d b i the F.C.C.at
13.56, 27.12, aiid 40.68 megicydrj. Micruwaves an 12.2cm long &d hilye a frequency
of 2450 cps.
Microwavcs are generated off directors doscribed as A, B c he mi spherical^ and 6 inch
diameters) and C and D ( d i w r a i 4.5 by 5
inches, and 5 by 21 indies).'The directos
are connected and coupled bx coaxial cabk
to the oscillator as is the U.S.transducer.
The term diothctmy is a mhnomer as the
microcurrents do not go thrMgh the bcdy
but similar to any current will tnove through
a volume conductor along the: lines oí least
impedance (resistance in nigh-frequency
fields) or across iq surface.
Diaihemy"
!
i
.
The curnnts generated inside a capacitor
field vary according to the cap-itor size, distance between the plates, mattrial between
the plates, and the voltage and {rcquency a p
plied. Undcntandably, these vahables c a n be
reduced. but the quantificatiod of the currmt within the field or-body il an avcrage.
No instrument can accurately :measure this
current. Meters on the apparatils only define
the "resonance" or tuning of the patient and
;:enerator circuits. The patterns: of the heatirix fields arc different for rondmser pad. iniductance coil. and microwave directors. but
11ie eRect is that they develop +at approxiiriately 3 cm belmv die skin's suirace. Micro-waves" are applied in a similar manner to a
Ilmp, and much oí the energy is reflected.
The heating patterns v a n w+h different
iiirertors hut essenti;illy diñer in the area
1 hey heat.
Wtrosnund"
is meck~nical oscillating
w aSound
r n ' ($00,
to i , ~ , a o Ocps and 0.15
qn) that produce vibration, shearing, corn" pressjei, and frictional force above the audible range (17,O cps) . The energy is generated by particlt collisions, each with different mws and energy state. With diflerent
pSrtKlss collidiag a higher energy is generated
tban ir c o n t a i d by each partick, and an
n(t&a&e reaction is produced. As the waves
ah muller than many particles, they will be
r(ftecte43. nKse energy reactions are mechani d an@ predominandy thermal.
Coupling or linking uitnaaund to the body
,nuface
transmission of the energy. A
'?gam ot gap ofi air will diuipate the energy
udd void ita dldct. Oil, j e i l i i , and water are
u s d as couplingi agents. The energy absorbed
by the tissues id tranunitted by conduction.
M e d i c implants, except those close to the
B k h , are good conductors, and their presence.
khcrefore. is not a contraindication to ultraiomd therapy, as they rapidly transmit the
h+t and do not reach toxic, temperatures.
NontHermal 4ffech. The primary energy
is thermal, but alteration oí mem@ucqi
brane configuraiion or pwible membrane
üeitruction can occur. Trapped gas molecules
W y exppnda~d.,coaiesceand with the interQoc reaction .contribute to membrane mpW e . T h e . oD&prarive-nnfaction phenamdnon cFtater. cavitations, which may also
Ilt¿r mmbranc or cellular functions.
dquip(neni a@ dosage. The generator
pduceai high-fri(quency alternating current
to dectrudes on &e piezaispric ciprtai. The
later may be quartz or barium titanate,
which is in the trAnsducer or treatment head.
ThP inttnsity is expressed as watts/cm-,
\di%h describer tite field of energy under the
ttansducer. It is derived by dividing the
rnarimal total wattage output by the sinc of
the applicator's radiating surfare in cm'.
ThJs a machine with 30 w m s total output
aid' a radiating surface oí 10 cm- has an
areage intensity of 3 watts/cm*. The sound
head must br raupled to the area undv
trtaiment and moved slowly to avoid local
buildup ol thermal reactions, which patienta
80
A'eiabilituiim
nic
'&ins
yili usu;rlly describe iis i.'iarp pain. Thetdosalpe
shoiild ' x at imzLkimxl icilerable leveb. This
will change along t t e ;¡ne of moveinent of
the tmriaducer ;ind cai be corrected by conwmittantly modifyini: tic wattage. TcJerancc
will inc:aasc durihg the! course of tre+tmeni,
and gmater in tansitiis may be apliiiid. Sessions up to 15 I O 20 n in may be givtn, and
several it day. 1:)aily o r .tmenrrof hvo WUons
often rrsolve a problei,i within 3 ti3 5 days.
Conirai ndicaiions
1 . The previrnisly m<:ntioncdcontraindicetions for heat tliei.apy apply to diathermy, microitienn, tnd ultrauund.
2. M..crothenn will lsuild up higtc timpcrat u i r concentratioi, in edema or on adhesive tape, wet dressing, and over body
prominencei
3. The precaution c<mnrerning deep heat to
a inalignaiit area is similar to ttwt PRvicusly noted.
4. Vltrasound will w t generate high ternperature in sur~iizlmetallic in>planta.
I.ehman'<' repoiti.d that any tfhipentuir elevation w.is quickly coiiductad
auay with no tcix :levels resultiilg. The
presence oi metal near the skin's surface
will cause ;i burn.
5. Bryan et al." reliorted electrorriagnctic
radiation ipterfe rence with cardiac
pacemakers in t h i , microthemi ftequencies. He noied thik effect for ovens, and
this precaution sh,>uld be obwnbd with
mimcrothemi diath8,'rmy.
Surnmaiy
The physiologic efiei,ts of conductive and
radiant heat, short-w.:ive. microwave, and
ultrasound are thermd. Their indications
and contraindications are essentially the
same.
The consensus is tha. diathermy and ultrasound produce their c'.nical effect solely b>.
heat production uittiir tissue. Ascribing an!other eflects to these n odalities is at present
not supported bv evidence. Modifying the
delivery of these. cnerg:i?s by pdws. Of other
hybridizations. does not alter their being
essentially thernial axcats.
COLI>". 19
Reduction of skin or body temperature is
usad i n rehabilitation medicine for (1) local
anal[:esia, (2) anti-inflammatory sñect, (3)
hypothermia for control of pyrexb, or (4)
posible control of spasticity.
'
Phisics
The physics of hypothermia is identical to
that described for heat with the patient and
the part treated acting as the heat source
and the applied object or the ambient tcmpetature absorbing the calories. The degne
oí temperature difference distinguidha hypothermia from cryotherapy. The former lowers body temperatun for extended pcriods
of rime (several hours). The l a n a uses extremely low temperarum (near or below
zero degrees Celsius) for a short time (reconds to several minuta). The tnnsmirrion
away of body t i m e temperature is by conduction, convection, or radiation, depending
on the calorie-absorbing object or material
and the method of its application.
Physiology
Reduction in metabolism with lowering of
entropy will reduce the mechanical, chemical, and electrical energy of molecules. Undestandably, intracellular and extracellular
dynamics will decrease as will that of membranes along their axis or at their endorgans.
Details of the specific physiologic reactions
can be found ih any textbook on these subjecls,".?*These are affected by the rate, extent, duration, and degree of temperature
d u c t i o n . The technic may be to the bady
surface or internally by cooling enemas.
The reaction to lower temperature ioully
is immediate vasoconstriction. and if the
temperature difference is signifirant (10'
to 150 c lower),
degradation or
cvoalobulin
precipitation
,,.ith
hv. . .
peieniiama). follow,
Systemic effects of hypothermia are direcied to,vard (1) wnse,,,ing
errrgy and
later ( 2 ) creating calories as they may elevate a lowered core temperaturr.
The ronservation mechanisms of the
I~
Prinkpie,
.
skin ase vasoconstriction and reduced
sweating. The cnrdiopulmonary mech+nmis
are bradycdia, hypocapn&, and hypoknsion.
The energy-creating respdnses are notably
shivering, where ATP-ADP exothermal reaction creates calories. The inability of infants to shiver contributes ib their poor hypothermic tolerance. Inmeabed fat metaboI i m OCCUR in the liver, t$e greatest k a t
generator in the core ana. ¡Fifty percent of
basal oxygen consumption 3 in the viscaa,
ñski*os
and 25% of this is by the
have hepatomegaly and prefer highdat
diets.
The subcutaneous fat actslas an insulator,
and when it is absent or deficient, as. in infants or debilitated patients,\intolerance b r
hypothermia occurs.
Neuromuscular activity is qodified by lowered action potentials and dqayed velocitits.
A l o C drop in temperatjre w
i
l
l reduce
conduction velocity by 2.5 t o 4 m/m. Muscle tension is increased and b y be due to
incrraaed spindle excitability, as well as 10s.ered viscoelastic properties of /theñber mokcules.
Analgesia is due to depreQed activity m
both endergan and fiber codduction. partsis or paraiyris m a y occur When myoneural
transmission is weakened, which occurs at
50 c.
The cerebral reactions maf include lethargy, narcosis, and dcpnssiw of neulohumoral activities.
Transudation is decreased p that edema
formation is reduced, a reaqion to h p
thermia that is employed in fireating acutc
soft tiuue injuries.
The toxic effects of hypothirmia or q w
therapy may be tissue da@. Fkfom this
occurs, ventricular fibrillatiop and shock
as a consequence of hypoten@ion may de.
velop.
When frostbite or severe hypothermia orcum, slow rewarming with s#temic fluids.
anticoagulants, and antibiotics ¡is the appropriate pmcedurc. Using ternperkturn slightly
higher than skin or core tirnpdrature is recommended for rewarming.
of pit )!rica[
rnrclicinc
01
Indiwiionr
As described, cold i:: employecl for ( I )
anti-inflammatory, (2: ;inalgesic, (3) antipyretic, and (4) antii;i>siticity ei'iects.
Anti-inflammatory effects. T h e application of any object COO'CI than an inflammtd
arca will draw off calo:ies and modify the
~prcgmsof the tiuuc reaction. This applies
to ( I ) acute reactions íiom trauma (sprains
or strains of soft tis.;ue muscles, tendons,
j o i n g ligaments); pliyiical agents, acute
burns (first or second degree), 0 1 infections
and (2) chronic c a p i l a r and soft tissue inBanamation.
An$-inflammatory eliei:ts of cold whether
for aüute or chronic diiorders include depresrieg of d physiologic tissue mechanisms.
V-nstrictirm,
edema, synovial tissue activity, leukocytosis, pr,molytic eruyme ac6vity, and other local 0 1 systemic reactions
are cadiiced as is pair. Bleeding IMY also
be rrdticed. Tmpcratu-e is lowered in acute
Ant- ind superficial ui:oiid-degret burns by
the iqmediatc applicaiion of ice and may
d u c e the degree of tisrue damage. The use
d a cold or a tepid wet compress to a moderately, swollen sprain will often prove very
hilpful,
Ana[geria. Cooiinp tit:?ar with vapor or
ice will reduce pUn úi rridiculopathies, soft
tissues, and johts. The niechanism for this
edect loas b w t ~ d p u i b t d . I t can often be
applied by the patient at home.
:An)i'l)ymtic &oct. Tlie antipyretic effect
of cooling, using either enemas or cooling
mBttmsws or blankets, particularly for rei r w t q tempennur elevation, is often an
~ffective adjuntt. The quadriplegic and
paraplegic may pnsent this problem, and
coding the patient by conduction will augmrnt aqtibiotic UKi'other medical measures.
D e failure of the autonorriic mechanisms to
provide adequate tem,xrature radiation
places limitations on this technique. The pa(ieht's skin may be incaliable of adequately
conducting the temperatiire. and slight gradients should be applied. The patients may
Oot have shaking chills or shivering. which
ir accounted for h i their altered autonomic
sympa-atic mecbanisrns.
82
Reha' iiotion medicine
This 11, I ,-ic of slow, g r d . i d &jing is
equivalen:
that dexribed by Simh Ba50
nirh in I:¡. Epiiome of H>drotheru&'
years agcs : the treatment of sun [htat:i
stroke. €ic :scribed it as the "St. Vifidnt's
Hospital" I ' , itment and covered the patient
with wei I 1 sheets. Other :Iimadd*g the
I
supportive ' ieasures for poshible circ&etory
failure, tiii~ is essentially what ir p r w t l y
ncornmei: J,
,j.
Spariiciiy Lowering muscle empáature
to 32' C: : I I affect the sensorimotor.ppthways. Gal--:xia fiber potentials, \<hi& initially ma', :e increased (shivhingl, arc
slowed aft?, 20 minutes coolint wi6 ice.
Neuromus:,. i.r transmission is iilOwe( and
ked.*' When niusck tc4ptrature appri:,? ':es 200 to 120 c:, spsticik will
be reduce11 : eliminated for s e v a a l h&rsZ'
Applying I.: I for acute "muscle spun!' pmsumes a pt iioiogic terning or "spas*" of
murle. Tli< benefits this niay &o&
are
more likel., . iialgesic as the path@logiq mndition is far i'om certain.
<\
Contmindi :oiions
1. Vasciil. ' : Ischemia, with inadequate
trans~ii~::
of metabolites to and fmm
tissue. ".ay become necrotic when mid
is apph d to areas with oblikmtife arterial t > . impaired venous Ohuk~ai.
2. Anestlis .¡a of an area may alovv lbnger
more o:ic e x p u r e to be t d h t e d
with I t ilting tissue damage.
3. Cold s. .tsitivity or intolerance: The
inabili:, of patients w,ith v;UCuli(is as
seen . I scleroderma, systemic lupus.
diabett!. and Kaynaud's p l r n 4 n o n
incluch both vascular and imidunologic f ton that rontraindicate the
use 01 ,old. The aged. infants, and
ratliei ,
debilitated individuals 'cannot t o ' . rate cooling. Brief ciituinscribed ryotherapy m a y be tolemtsd.
~
mactions with urtiqaria,
. Constii I I lona1
purpura .and possibly coliapsC m a y occur.
4. Indolciii wounds will be further aomproinirir by thc vasomnstrirtive &ect
of c o d i , and healing further delayed.
i
~
.,
Sourcbr
other <'
haring I
tuni oí I
w its I
Va$or-coolmt or evaporation techriique
uses ahyl chloride or fluorimethane sprayed
on t h t ama to be treated. Opinions v a n
to whether a f r e t should be allowed. A'
modes frost accmnplished by holding the
sprayT.TmP2 leet fmm the a n a after a 15to 2oaCc spray wñl be tolerated. Repea!.iiig
this two or three times at IO-soc inteavals is
an adrquate treatment. This should produce
analpeia and permit stretching and deep tissue massage, as it may relieve pain in "trigger" points or muscle spasm.
k c (packs, bags, or compreasu) cdn he
applied to an area for 10 to 15 min, takw
off, and reapplied after a 5- to l C 4 n interval. Repeating this t h m or four .times
will ohen be effective in acute sprains and
equiltior.
Planck's
t i m a tli
r n t that
ir severi
light or
peiiCtrat8
dennis.
qu3ntun
iral) ch.
produces
tropy).
As thi
Stninr
Imncnion of a limb in ice water may be
tolerated for only 1 min. If repeated with
intervals similar io the technique noted for
"solids:' it may be equally effective.
Cooling pads or blankets are attached to
pumps of cooling liquid (saline, alcohol:.
The period of application varies with the patient, aystemic tolerance, and pathology being treated; it may be several hours.
,.
SUMMhRY THERMOTHERAPY
The :physiologic effects of superficial heat
are subcutai~a>usvasodilation with elevation
of mctlboliun
or tempenrun in cellular and
i
I
extracellular compartments. "Deep heat"
may elevate muscle temperature with transient metabolic and vascular reaction. The
analgesic. spasmolytic, anti-inflammatory,
and soporific effects of heat remain the predominant indications for its use.
Cold is anti-inflammatory, analgesic, and
I
capable of producing varying degres of '
maesthtsia. It depresses metabolic activity,
produces vasoconstriction, and may r d u c e
spasticity. It is often used in acute soft tissue injuries.
ULTRAVIOLET RADIATION',
Biophysics
Is
Lhaviolet rays range from 180 to 390
nni. Their optical properties are similar to
I
lengths
disrribec
wavcleng
is accom
rractiom
.Asorbin{
a photos
r i i t e cal
nf other
.qroitnd s
drugs. or
ir the tra
rereptors
neurouid
mitten f
pituitary,
areas deF
melatonic
fluid. Th
artivity 2
in the OK
alands.
Physiolog
Pimetra
o.I
nlnl.
iiriiip.
,
'l'lir ab
proirins 4
rhcrniral
iannitig, I
-idal cWet
' 6 , ri~uro
Pri*cipZes of
other electromagnetic wavca but d a t a
having photons of greater + n e w , The @antu”, of energy of a photon] ¡a direcdy related
to its frequency and is kxprcued by the
equation € = hn or ene
in ergs equala
Planck’s constant h (6.62 x IO-*’ U ~ . S C C )
times the frequency per W n d . I t is apparent that the energy of the h a v i o l e t photon
is several fold greater th+ that of vüible
light or infrared. Ultraviolet rays will only
penetrate to the capill+
bed of the
dermis. The magnitude of the ultraviolet
quantum will cause chem$al (photodrmical) changes compared td i n f r a d , which
p d u c a essentially moleculir excitation (entropy).
As this energy vanes wid) different wavelengths and molecules, aciion spectra M
described that indicate the rnmt ef6cknt
wavelength for specific bioi c effactr. T b
is accomplished by either rect or indiect
reactions. Direct reactions becur when the
absorbing molecule change( chemifally or
a photosensitizer is raised t o / a h i g h enegy
state capable of catalyzing the oxidation
of other compounds bdo* returning to
ground state. Photosensitized may be foods,
drugs, or disease toxins. Th¿ indirect efftct
is the transduction of light &e%/ in photoreceptors (retina) into n c ’ r a l signals to
n e u r c e n d d n e pathways i d neurotransmitters .in the hypothalamiir, spinal c o d ,
pituitary, and pineal body. ;These effector
areas depkss the synthesis ahd secretion of
melatonin in the blood and cerebrospinal
fluid. This results in elevatien of pituitary
activity and consequent hohonal activity
in the ovaries, adrenais. and other endocrine
,<lands.
$I
8”
Physiologic effecfs”
Penetration of ultraviokt is iapproximately
0.1 mm. varying with skin thidknss and coloring.
The absorbing substances in the skin a*
proteins 0 1 nucleic acid, and the photo,chemical reactions are ( I ) drythema, ( 2 )
,!;inning, ( 3 ) epithelializa~on,‘(4i bactenoI-ida1 effects, (5) vitamin D, kyntheris, and
6) neiimhurnoral effect.
:
physical
medicine (it
Erythema is noted within several h o w
after expos*
and is maximal at 24 hours
I t is d w p -direct or therm& effects on
capillaria ahd the possible release of toxins such as histamine, serotonin, and
bradykinin. This mpons( is used for. dMaga
control; the minimal eryrhemal dose (MED)
being the minimal time of exposure to
give the faintest reddening effect 24 hours
later.
Tanning is the increase of melanin granules in the prickle cell layer, which contains
keratinmyta: One or two days after photooxidation, mlanocytes divide and secrete
melanosome bodies, which contain the melanin granule8 and depasit them into the
,keratinocyte layer. The action spectrum is
:between 253 and 296 nm. After 2 to 3 days
‘the tan f a d a as the kcratinocytec dough
off. Tanning may provide some protection
against ultra*olet radiation.
€pitheii<rliz~tion,or carnification, results
from accekMed cell division of the epidermis. This may, with excessive exposure,
80 on to desqwamation. The thickened skin
with modification of sensory transducer activity may itch less or be less sensitive to pressure and thus be of benefit to orthotic or
prosthetic wearers.
Bacteriocidal effects of ultraviolet rays ocour in the 260 nm range. The energy slten
mitosis or m y produce lethal mutations.
‘ h i s effe.ct can be beneficid in treating Qpen
skin wounds or infections.
Tllaniiti D, (cholecalciferol) in the skin
and subcutaneous tissue is formed when
7~dehyocliolestcrolabsorbs ultraviolet tight.
Wunrnan’ describes the better ability of an
erperimental gtoup of men in a soldiers’
heme to absorb calcium alter daily ultraviolet irradiation. Csing total body irradiation to modify orleotnalacirr is endoned by
odier studirs described in his article. Its
use in geriatrir practice should be encournged.
The ncurohunioral action of ultraviolet
li&t has been described above.
The toxic reactions to overexposure to
ulimv/olet light are bum, usually from wavek%thi of 520 nm. This is either deliberate
RrhPbilitatioh rnrdicitu
84
or inadvertent. thq hitter due tcWns#tiitiond
Overcast clouds q d tr? mfkCt& fr4.1 sand,
:ommon ccinplihtion
in
.~
reaction iC conji(dtivitb
~
tivity
to
uitravioidt light arc
n)
~
foil^:
I. Pain
2. Edmn
9. Bulb formati+
4. Fcvn, chills, + a h
5. Conjunctivitis j and/or photofihthdbb
6. Desquamation
7. Infutim
8. Shock, puibld death
Chmnic overc&surc
lowing:
can l a d td &e fol-
Gmcn m p
Mcthylcnc Mue
Coal tar
Tetracyclinei
RitnRavin
Methotrexate
Quinine
Sullonamide
Phenylbutazone
Chlorpromsnne
Barbiturates.
Heavy metah: V I
I
I
Sources
The
I
of I1
cury arc lamps whe: I 1: r
sten cathode iimize c, :!
new, or mercury VI 11
diñkrent wavekngth ) I
cenvation in t l r ult-. i It
either under b w : I s - . I
where the electroii :I ,I
thah the mercury viii , ' i'
pressure-hot Tart:'. A I ,
Rating the pmurii
I!
1Cd atmospheres will I . ii
without affecting thi: ) :
in the low-pressure : 3 $:
and require high \ ! I i I'
low voltage.
The enveiopa ma. , ! I
hipti silirate, or (::I ' i r
Some m a y be eoateil ' I 1
staks, silicates, bot: ! !!
mapesiwn, u k i u i n
i '
Thtse reernit (fluores ' ) :I
lengths of mercury 1 z , ;<
additional broader I n ' k
cluding visible rays , ', g i I
Rector directs and I: : :I I
)ligh-prerrurr h c ! I II
broadband spcctrui. i
3
cidal effects.. e#vthei
.
,
I
.
cooling jacket of :..
(Kromayer lamps) :
tion to the skih.
Cold quartz m c v
radiation from the9.e
253.7 nm (bacterh
w k n . air stdimti.:
oxide glass (Wood';
WAUICa
Di**U,S
Endocrine
Insulin
Thyroxin
Epinephrine
-
RtuiPin
Meuboñc
Pellagra
Eythropoictk pmtoporphvh
Porphyria
V.xUlitis
Scleroderma
Lupus-iyriemic, divoid
Polyartrriti. hoioia
Polyvinyl chlbride
In/rrrio"r
Herpes
Tuberculosis
Cardiorcnil /oilup
Dtrmaiologic dirtnicr
E m i
Urticaria sola+
Hereditary xerbdcma
Vitiüjo albinijn
Epidcrniolysir bullcua
Drqs
hain
Perfumes
,
.I
'
~
Photosensitizers bf ultmvioleb hhb
I
~
I
!
, I ,
.
I
..,
I
.
,
!
I
~.
.I
jl
I.
I
.
I
Y
'I
, .
:;
I
i
,
I
.I
~,
.
,.
'
i
~
~
18
IC
i!
I
,
,
'.
i:
)
,
,
,. , .
sure cold quartz lanip t&+
rays of 570
to 380 nm, which i-~usehair F e t e d with
ringworm to fluore~~:e
a bright(-.
proferraond modclr are iarget, take higher
power, and can cover greater
Lamps
used for general irradiation; have tuber
wound inta coils, and for oridciai or sinus
tract irradiation, straight tubes,
Suníompr, which are silica glass tubes
coated with phosphors, arc u + l l y several
bulbs racked in P refkctor and /are available
for home or solaria use.
spectrum of 280 to 350
erythema and mild
b.
indications1'
The applition and employnlmt of ultraviokt therapy in rehabilitatiod medicine is
for ( 1 ) bicteriaidai effect, (2) epithelia&
zation, and (3) cakium me")1'sm.
Using ultraviolet therapy ad nctively for
routine wound c a n will
rolving refractory or indolent
cubitus or vanfow ulcers
After deansing the areas with
c a d whiripooi, applying i d ultraviolet
four to five times (MED)dail will d u c e
bacterial infection and encoura& epithelialization. As the wound
theraw should be
wound to avoid ovcrexpmun ar& bunting of
6.
intact skin IS neccstary.
The exfoliative, epithelializati+, and bacteriocidal effect of ultraviolet ys, particularly to an inflamed stump, may improve the
resolution of skin reactions such qs folliculitir.
Depression of sensation and i n d e a d mkrance for prwure of brace ba&s has been
dixusud.
The use of general body ina ation to enhance calcium metabolism, pa
I ticuiarly in
elderly, infirm, confined patiend should be
encouraged. It is a relatively +y, inexpensive technic and may help seduqe the problem of osteomalacia, although !the role of
vitamin D, per M is not the tow1 answer.
The recent developments in dare for the
1
Qo~traln#ictation~
The described toxic ph,>t<5-: i I 7 :I
diseases, or drug. d i i h
i4dkations for udng ultra%i I(
of {wd,
\
F?*btrlpt¡on
14 dequires descetion 0 1 tit: .: I! ii .
qfsehcy ol the trtatmnts. TI :ii ti " :
tqe aource must dways bt
¡{the apparatus has powe. r t i i l i s ::I.¡!
I
8
a$v(ys be the same. The <ditii.
a'ic
I
tion of the source to'the p iit 1 Iii :
i&&sit)-.' The inwrse sql:ai ,! I;_I :i I!
ifthe di$tance fmm the I in1 I:) ti
slrfiice is decread by one [.ill 'IC !i
of the radiation ir quadriiip ed,
hmbert's cosine law stí te
I th '
:
e l l u g y sttiking the skin .lit z ,
1 it i
i :
805; at an angle <if;I)'' I N * 1
The application of SIX :!fit
li I
a q r ' dressings should br r,cl t !IC
pmtription.
( :
~
a".
~
I
86
RehabiZitniion medicine
.
Ssummary
Ultraviolet light provides photochemic.al
r4ractions in and on the skin, which in r e habilitation medicine are employed lo:
bacteriocidal and epithelialization eñects and
vitamin D, production.
The application of ultraviolet light in tlir
case of psoriasis and hyperbili&binemia 01
childhood suggests possibilities for a wideriing application in clinical medicine.
ELECTROTHERAPY
The clinical applications of electrotherapy
pi~sentlyare for ( I ) motor disturbanccq (2)
pain, ( 3 ) pacemakers, (4) splinting, (511
spasticity, (6) biofeedback, (7) electrophoresis or phonophoresis, and (8) diagnosis
(see p. 3 2 ) . New developments and techniques in medical and surgical management
of peripheral neuropathies have impmvcd the
prognosis for many patients with lesions previously considered incapable of any benefit.
Motor disturbance^.'^^ " Denervated muscle demonstrates histologic changes analogous
to atrophy of disuse such as ( I ) decrease in
fiber diameter, (2) proliferation of sarcolemmic nuclei, ( 3 ) loss of striation patterns (late
in atrophy), ( 4 ) thickening of intraniuscular
arteries, and venous stasis, (5) increax in
connective tissue (late in atrophy), and after
3 yean, (6) possible dissolution of muscle
fibers, with (7) residual fat, blood vessels,
and connective tissue in the area.
i f reenervation occurs within the f i s t year,
a fairly good functional recovery may be
achieved. The prognosis, particularly after 2
or 3 years, is bleak. If the atrophy can be retarded in some way, the degree of recovery
may be increased.
Electrical stimulation of muscle is used to
retard these changes. Because they occur
rapidly, stimulation should be started at the
earliest opportunity and given several times
daily if possible. Studies both in the laborat o n and clinically indicate significant retardatioii of atrophy i n treated peripheral nene
lesions. In addition to modifying the noted
histologic changes. chemical and enzymatic
rliariges are also retarded. Extensibility of the
muscle is better. 3s is its vascular dpxamics.
Principler
or incontinerice control have been successful.
These technics are limited by the tissue tolerance for the electrodes and the problems of
power source.
Electrophysiologic splinting. A stimulator
to activate the tibialis anticus and foot dorsiflexors at swing-phase to modify foot drop
has been used. Similar technics to activate
muscles of the upper extremity in quadriparesis are reported. T h e tolerance of t.he
skin and patient for these devices is limited
and not widely accepted.
Sparíiciiy. Tetanizing current for the control of spasticity by attempting to fatigue a
muscle U unwarranted. Alternative measures
are more effective and less painful.
Biofeedback."~ Biofeedback is the term
applied to a training technic that attempts
to modify autonomic functions, pain, and
motor disturbances by acquired volitional
control. Using monitors for such activities as
EEG. ECG, or sweating and demonstrating
the physiologic. activity on a screen or with
audioamplification can help the patient acquire an ability to lower his blood pressure
or slow his pulse rate, respiration, spasticity,
or autonomic functions. That every patient
cannot succeed in these endeavors and that
some of these functions are beyond conscious
control limits the use of this technic. It is a
means of expediting "behavior modification"
to achieve tolerance or elimination of undesired syndromes. coupling the patient to
an electromyograph and having the sight and
sound of action potentials presented and
using these .stimuli to restore or control
motor function is a variation of biofeedback.
It is essentially a reinforcement of muscle reeducation when used in treating hysterical
paralysis or for paresis following varied
neuromuscu~ar-musculoskel~~l
disorders.
The staff, equipment, and time required
for providing this training restricts this procedure to programs designed and equipped
for this purpose.
Electrophoresis or phonophorerir",
Iq
Electrophoresir or phonophoresis drives
molecules into the skin by ion-transfer with
direct currrnt. or by ultrasound mechanically.
of
physical medicine
87
The necessity, effectiveness, or value of these
technics is questionable.
MASSAGEU-']
Massage intelligently applied is an effective modality. Fuller explanations and descriptions of technics are available in many
sources.
Connective tissue massage". " is a stroking move along "reflex zones" to achieve
metabolic or vasomotor reactions in the area.
T h e evidence that these reactions actually
occur remains to be documented satisfactorily.
Physical principles
The physical principles of massage are to
stroke, press, knead, rub, pound, or rhythmically beat the skin and underlying tissue.
These movements can be augmented with
hand-attached machines, or by machines
alone. The pressure can be vaned as can the
force of each of the movements.
T h e physiologic effects are as follows:'5
1. Skin: Reactions oí hyperemia due to
irritative effects.
?. Senmiion-pain: Analgesic and soporific
effects are quite often noted. The analgesic
effect of stroking or pressure on muscle cannot be explained by modification of an intramuscular pain fiber as none has been described. For the present, reduction of &in
pain fibers firing must be considered the
explanation for analgesia.
3. Muscle: Reaction to pressure is related
to the effect on the vascular and lymphatic
systems. Compression will produce an intravascular ischemia and extravascular fluid
movement. Whether kneading or deep pressure breaks up "fibrositic nodules" is questionable. The existence of these tender spots
is acknowledged and their alteration oí size,
sensitivity. arid occasional elimination by
massage is noted clinically. What exactly
they are and what is happening is unclear as
is why they come bark. Light stroking, fingertip massage over a sprained tendon or
ligament is often effective but similarly unexplained.
4. I'arrularr The effect on vascular and
88 Rehabilifafion medicine
lymphatic disorders is essentially transient
and if desired should be accompanied by
supportive pressures from elastic coverings,
compressive apparatus, or positions favoring
drainage when edema is present. Reflex
vasomotor reactions following connective tissue massage are described, but this cannot
always be achieved. T h e use of connective
tissue massage” in these conditions should
be restricted to selected patients who after
an apparently successful trial are given a
course of treatments.“. *’
5. Prychologic: The relaxing, soporific effects of massage are widely recognized. This
may be better than sedatives and often will
be the most effective measure in relieving
muscle spasm, tightness, or “tension.” T h e
explanation of this eñect remains empiric.
Suffice it to say it works. Unfortunately,
economics force us to w tranquilizers, reiaxants, soporifics, analgesics, or narcotics where
massage might be as effective as any of these
drugs.
lndicaiionr
stmtching of muscles fcKi , i
pressures above and bel.:>;\
Prior heat, massage, aii8:i
effectiveness.
A review of the t c i .
I
exactly what is orcurn:ii: i ,,
vague and cannot be i m ( i
many instances. The clirii , ! ,
manipulation in refracti.,,: ; , ,
and back pain cannot I> ‘1s
procedure coirectly ern; ,I, , , (I
selected and prepared !I
prove its value.
Specific descriptions of
I(
found in references 42 i t u
,
.
. ,.’
’:
,
I
,,.,
:
I.
11,
,
I
1
~
.
’
c,.
# I !
v. , , I I
I.,
I
!
, ,
I),
.v.
i
,
I
,,a,,.
STRETCHING
S t r e t c h i n p 30 atternpi,.
articular snft tissues, teriil.
muscles by either m r i i i ;
means. Its application in i t ’ ,
problems where motion is i
effective.
The contraindications a-,
tion, sprains or strains, ! I
painful musculoskeletal,
.
,
’
r
I
‘!I ‘11
i
.)I.
,
, I
, (I,,:
,
:I>
.:,
.<I
I ,
‘ I ’
:.
.x’!1
I
,
1 1 % I.
:,
I,;
Soft tissue injuries with pain, “stiffness,”
and “spasms,” are the classic pathologic conditions for which massage is ordered. Psychologic muscle tension is equally benefitted.
Articular pain, with or without swelling, can
also be helped, as can arterial or venous i n sufficiency (not when inflamed). Scars may
be loosened and capsular “stiffness” (after
immobilization) reduced. Massage after exercise, stretching, or vigorous activities is also
effective.
The technic is the app:li,i
ing movement using courlie : , .
tiefit’s body movement. K
i
anatomy of the tight stnu t
tendon, or joint capsule ui ;
sired movement. Preceding
massage and an analgesic (
hance its effectiveness and
.:
and duydtion of any afier F ,
Contraindicoiionr
TRACTION5’
Soft tissue infection, hemorrhugic or clotting disorders, or inflammatory disease of
muscle should not have massage.
: si>!,
A counterforce of up to ií
.!
to the ne&, or 100 pounclr
used to stretch perianicu1,;ir
purpose is to distract verteti;.; 1 1 I
. ‘I I r ing neural foramina or pow\ ’ I j
I
:s,:
herniations. Pain in the
1
111
the diagnosis “whiplash” 01 ‘ , ,
.
may be benefitted with t r , a : ~ ’
: I Y i:
be manual or mechanical. t1.t
:. 3 .
spinal muscle tension or pau
,> I e!
ficiai.
, I , ; <:’
The.indications and coni!: I I i
MANIPULATION MANEUVERS
Manipulation maneuven include gentle
stretching of periarticular tissues and is
achieved bv the application of manual pressure and then counterpressure, and sometimes a “click” ir noted. What this sound is
remains obscure. It differs from stretching
and traction as it is the brief tensing or
<li.~
>
1
eases.
I
,I,.
1
/,:I.
11 ,
:
t.
I’,’~:II~
18il
1
~
8;.
‘ I
,
Principles of
s.milar to those for "stretching" ;u is .th
.y-eparation of the patient.
ItiJLES TO APPLY WHEN ORDERING
I>HYSICALTHERAPYw
1. D o not use physical therapy if medie
I
{
tion, surgery, or psychiatry can be mera
effective.
2. Select the simplest, safest, lust corn@cated modality, rquiring the rninintal
involvement of personnel.
?. Use a device that allows easy observetion of the treated part.
4. Use home therapy whenever posible.
5. Have specific goals.
'
6. Limit the number of treatments, and
if no benefits are noted consider the
following:
a. Repeat the series.
b. Review the procedure to ensum that
it conforms to your order.
c. Change the dosage or frequency
(two or three times daily, 5 or mom
days a week).
d. Discontinue the treatment.
PRECAUTIONS TO BE TAKEN BEFORE
THERAPY
icd
p
in i~tbpoksand man
a!
1
medicin,, 1!
Referral
rrg ' t e i d therapist is I , :ommended.
ski1 and training of re; , <redphysical
VA:
I
Ti t
i.nii
patianal therapisYa _ I I'ensqe that ht!
pat ' nt will get optima' , nd efficient ciln..
The r role as instruqto. nd supervkir c '
thei. py *des, family, ai !I patiuit is i n m U..
able and; when M 4re i(.i, can save t i t 1
and reduce the costs of I i:atment.l". **
occ
OiIAGNOSTIC TESTS
Tile mwitoring of ene. L:' transductiori I' :.
quir" a scnwr that tar ruansdua the
IKI.
a visible mni. "1i3 u ~ % y
may I e
dhmlly r(C0rded from ' ! I S body's surba<e
Y iii thmcgraphy or &Ittmohmmetly ( r
Ruor.-ccnac Y in the u.i~.viokteffect 0 1
the 18' ions of ringworm.
1a;'osing an energy s
onto -he body surface 1
$OB ~"nagriphy where tf .. knrities of di !
Oaue trari6mit different i , t ' nsities of sow(
wave: to a sensor that ci ! ~ e r t sthese -ir¡
atoni to visual records
Oh-rved reactions to r..,t or cold suct
as bli' d prssure change Aanges in thc
acdon potentials in myutl I ia gravis, or in
newo. sgic findings in mu I i le sdemis are
vabaal e diagnostic aids.
Bint..ly the reaction of
to tleí 'rica&stimuli of var !r ;strength a i d
duratia ln can be used to tscl I. I sh the strength
duratii,:~
CUM with the: d , : c : 1 e
valwa. s4
The: nogroph scans the 1' in nnd wan+
duces :.IC emitted i n f r w d
tia in" light, which is re( )r,led on a filni.
The di,iails of the technic 8, '; deWribcd i.n
denens ': 55. The merits o1 ii:k tshnic are
( I ) its dety-the patieat : : ot exposed to
any ioi .zing radiation, (2) i s lack of ail
intrusivr component, and ( , the v i d l a .
tion it ,tllowa of vascular a d inflammatoq:
technic5 An obliterative lesi' 811 can te cad!,
reacúor not easily acc&blf 11 radiognphic
identifie' without any coot1 ,st requed.
Derm hmmetrysa is an e (N lid art of
skid resi :ancewhere the cor~:ii.bivityof the
skin is 4 e c k d by the &i,:ipe in N m n t
Aow wit! any autonomic or -,eiipheral neu:O
I
I
i
I. Sensdion: Anesthesia is not a cmtraindication but n q u i m a careful monitoring.
2. Comprehension: Ensure that the pati nt understands what the. usatplent,
ikolves and how to signal k any dUcsmfon develop.
3. Equipment: Ensure &at all \run, huting elements, bulbs, switches, dials, and
timers are in working order and in the
off or zero position when treatmeat is
started and ended. Apparatus should be
unplugged when not in we. Only use
"underwriter approved" equipment.
4. Dueare: Caution as to the dosage for
debilitated patients, these with sensitivities, vascular disease (Raynaud's), or
edema.
...
A description of the technic and application of each modality díscuwd can be found
i
~
'8
!
*j
;dying two +res
xant voltagd 2")
cold skin will )\.uaEe 1 m q o h d @d moist
warm skin 1 4 2000 ohms Daklfrom an
u
t
e to
Lnaffected a 9 or foii&ing w
heat will p.d,le comparadve @$es I,t is
painless, r s y to perform, and thej 4uipnient
thenia gravis c1icii.s a decremtiit o( . I '
$on potentials after tlie third :o i5fti.i i i 'I.
Ius. The pomtials ai? restond tn 1::s :1
the muale and decreased with N: '1.1 c.
mggcsting that quanta of transmit-.i . I:dance may be stored with cmlirig ','
Lorn uait testing:'", This ttxhni,: ' ! ' < ' .is
+e strength-ánd duration of stini.ii
it
dicit a minimal twitch of a mrget I I \ I ' ?.
The stimuli are applied to eitner i h t 3 1 , .,e
or in denervation. to the muscle bel:
Recording 'the values on a graph 1) ' 3 . <:E
a c w e for each tissue that is difi'e < : i i , til
hlues. The details of the method
I rforming the test are available in r e t ~ i e ':e
61. The test is relatively simple to ]:>I ,+lo11,
qmderately uncomfortable, moderai.i1) itprcduci%le, and nminvasive. It has f i '11
into the +adow of electromyographic ! 111 I ,
but there am occasions when it may :e I Iployed. Using this technic in the first k. i ii
uuks after birth may provide sidequa I : c: :i
in pediatric patients with fac.ial pal ', . d
not require needle insertions.
T-
;
, !.
',
i
1 1 '
however to pr+:oke a sus
RFElENCES
I . Momwitz, H.J.: Physics of ticit. In It, 1peutk heat, Baltimore, 1963, ti. Liiht I I I I t:.
Licht, Wavcrly Prerr, Inc., pp. 1-23
2. Fucher, E., and Solomon, S.: Phys+Ih+ 11
mpomes to heat and cold. 'In Thir: i 1,.
heat, &)timOrr, 1965, S. Lichi and E 1.i t,
Wiverly &as, Inc., pp. 126-169.
9. Green, D.:E: A framework of princi 114s ir
the diagnosis i.f ringworm has been #dethe unibqtion of b i a n c r @ u ; the r v , 11scribed.
i n i p of energy tnndvctiorr in hi iIv8 ;i1
Applying he+: to a patient 4ith ne~+msystem, Ann. N. Y. Acad. SE¡. 2: 1 ti í,
murular dised-e produces' alt&qtions of
1974.
4. Stillwell, C. K.: Therapeutic heat. I n €I; .I.
book oí physical medicine and rchilii i i i i t ~ 11.
Philadelphia, 1966, W. B. Sinnders C ) , , 1:
notable sensiti4.y to heat apmu&,,and this
235-243.
fact is used in /')any clinics b a +r¿vwtivc
5. Castor, C. W.: Connective tir.sue PCI 1.2 I I:
test, where thá patient is e$poaeH to Mist
the cñecu of temperature studied ni ii '11,
irily sufficient t0,rjiSe Wy
Arch. Phyr. Med. Rchsbil. 57::s-1I, I I 7 i
.
Irquently, tCmp<ltaly e&
6. Genten, J. W.: Eñcct of ultrasound on r n ,ri
geration of
U p s as visual aguity or reeitcnritiility, J. Phyr. Mcd. 94:?6?-XiI, ! '1.
7. \Yurtman, R. J.: The effects of light 1 ~ ~ 111:
apprarance of
previously noted sisn $at
human body. Sci. Am. pp. 69.2. Jui), ! 'i,
may have subsi ied will OTCUT. It ris felt that
8. Sinmns, D. G.: Muscle pain sb-ndronii !, , .).
these reactions .ire almost qxclu$iw to paJ. Phys. Med. 54(6):289-308, 1975; .i!41
::
tients w i t h d e 4 elinating distase of'the otn-15.45, 1976.
tral nervous sy6i.m.
B. Millard, J. B.: Conductive hcntirir ri
The rcpetiti\lb stimulation t a t ip 'pyasTherapeutic heat, Baltimore, 1965, S :, !I:
ii:
sues
1:
I
4,a,
Ud E. Licht, Wavcrlj PITS, inc.! pp. 2x)251.
IO. Zidu, J. ñA.: Hydn>th/npy. In HanU><nkpf
p h p i c d niedieine and rchabilitntbn, Phi@.
delphin, 1966, W. B. Qiundcn Co., pp. 3 : s
339.
I I . Lowman, C. L., and R+n, S. G.: Thcapcu/c
u* of pool and tmkk, Philadelphi3 l9:%?,
W. B. Sarinder. Co.
12. Stoner, E. K.:Luninot$ and infrared heatii?g.
In Therapeutic heat,; Baltimore, 1965, 6.
Licht and E. Licht, Waverly Pms, Ibc., i'p.
256-265.
13. Lehnun, J. F.: Diath*my.
In Hindbook bf
physical medicine andl rehabilitation, Phibdelphia, 1966, W. B. Savndnr Co.
14. Scott, B. O.:Short w& diathermy. In The*pcutie h u t , Baltimore,;1965, S. Licht and $.
Licht, Wrverly Prc5, Dic.
15. Mmr, F. B.: Microwav( diathermy. In The*peuaic heat, Baltimon,iI965, S. Licht and t.
Licht, Wnvcrly P m r , jnc., pp. 310-320.
16. Lehmin, J. F.: Ultruo>)nd therapy. In The+
putic heat, Baltimore, i1965, S. Licht and E.
Licht, Wnvcrly Press, Gc., pp. 3?1-386.
17. Bryan, P., Fuman, S.,' nd Escher, D. J.: laput signals to pacema en in r h m p h l C.vironment, Ann. Pi. Y. Acad. Sci. 167S23-
c
824, 1969.
..
Iar. pp. 502-537.
i
20. Nigbtingte, A.: PhysiIs rnd electmain
- i
, , phy*ul medicim,
Y&, 1959, Tt@
2
.- ..
.
Mianillan
.? '21.~ Scott,
co.
P. M.:
dall k Cox.
j
I
!
1.
390423, 1959.
23. Baruch, S.:¡ An epito e d hydmthenpy,
Philidelphlli, 1920, W.fB. S.unden CC.
'4. Chitfieid, P. O.:Hypo+ennia and ir< &eca
on the sensory and pc herd motor system5
Ann. S . Y. Acad. Sci.
:+45-44ñ1 1958.
2.5. Stillwell. G. K.:Cltravi,let therapy. In Hind.
book nf physiral rncdicibe and rehabilitation,
Philadrlphui. 1966, W. $. Siundrrr Cc., p p
340-352.
!
26. Fircher, F., *nd S < + m q , S.: Physiol»g¡c el.
f c c u of ultraviolri radidtiun. In Tkr-tic
clcctricity and ultrarialet radiation, Balti.
T
mom, 1967, $ i . ~ t h tani I! Liihi N a v i . ,
Pres, Inc., pp :!--7-$:'
?7. Scott, B. O. <:Iiiiciil ui.w o í ultravi(di.t rat1 I
tiun. ht 1 . 1 i i i i i i i i t i ~V
. I ctricity i ~ w l 111:1 ,
violet radiatiimr:. S. Licht and E. I. cht, 'I\ I
rerly Res.,I n r i . pi>. 3:!5 17H.
28. Pnrrirh, J. A,. l'!izp:itni, :. R.,? a i . n ,
L., an4 Pa I t a h , hl. A. Photc<h<,ri
pu>iar$ with < . a i d rii.tho d i : n a>,d Ir,ngw.i.,
ultraviolet 1iF:hi. Y. Ens1 J. Mei.. l!ll:lC!:
1974.
29. Crcmcr, R . K... f'errynai, P. W . . ; n i R i : , ,
a d s , P. U.: T h e iirAw m of hgl-t on . I
hyprbrlirubiiiaciiia of nfintr, I. u m t
I!l94-16397, 195F.
30, Guttmn, E.: Hirtol>li>gy< I depencr;~t.ona i I:
repeneation. In Elcarodi bsnol;i .mi elect. .
rnyogrsphy, %A
H;<mn. Cain.. l!l6l, .
L i c h t . n d E. Licht Publii ley, pp. 1'2-133
31, Stillwell, G. K.:Cliniial e , x t i c a l stimulstii,
In Therapeutic: electrici y and I ltraviol I
ndintiw, Balti,iom, 196 , S. Lich.. and
Licht, Haverly :'ress. Iric pp. 1Oi.'55.
32. Pain sympnsiu.x: Sitrg. PIeuml i:61-111973.
33. Sweet, W. H..arid Wcpsic J.: Contri I of pziii
by focal electri<;il stimuh ion for auppresii<,
Tram. Am. Sciirol. Asso< 93:103-10i, 19ti
31. Taub, A.: Elrctri,A atirnL ation fcr ,.he relibl
of pain: two le\rons iri te< inologi<al u:alati.r
Perspectives Bicl. M d . l ! ' ( l ) : l 2 5 . l5,
~ 197:
1976.
:M. Mrlznck, R., aiii \Vdl, 1
.D.: Pkii mcch;
nirmr: a n e w theorv. Si erice 130 91i-9;!s,
1965.
36. Jacobs, A., and I'<:lton,C. S.: Visual ftedba:l.
of myo+tric
itpur tci I acilitatr n-u:,cle
lnxatiom in nomal perron and n;s.titnu w i t . ,
acct i~]urks. Ateh.~Phyl.Mcd. Rchkil., p1
34-39. fan., 19(i9.
37. Shapimi D.,and Schw,irtz G. E.: Iliofccdba.:i
and v i r e d learning: c1,nic.l app i'atioi,
Scmin. Psychiatry. 4(:?):l 1-184, 19ri.
38. Harris, R.:Iont<>phora:iis:1 icrapeui:ir electri<
ity and ultn?:iolrt radiatia 1, Bdtir>o.e 196;.
S. Licht and E L.icht, \%avcrly ,?nI!, Ini
pp. 156.17ü.
39. Stillwell, G. Ii.: Elwtric,:l stimulation arm
iontophoresis. In Handboo>. of physical medi.
cine and mtirbi:itatim. I hiladelphi;., 1965,
\V.B. Seunden IZO., pp. Z j3-359.
40. Cyriar, J. H.:Clinical app cation <,I n.irsap.:
massage, nianipiilatior, a: d t r r i c i I, New
Haven, Conn., 1960. S. L chi am1 ::. Licli
Putilirhcr, pp. 1:!2.144.
il. Fnnrun. F.: C:.:iissical ",assage tc,.hniqu,i
m a s i p e , rminipvlntion P I d trnciio:,, Ne.&
Haven. Conn.. I!J60, S. L rht and E . Licht
Publisher. pp. i 4 . K
<I
43. B i d o f . 1.. S.4 and Elmintime m u u q In Uun&e,rn
traction, New! Hawn, h n . ,
and E. Licht. PublLher.
44. Ebner. M.: C)nmctim tulus m a
Hunt
ingron, N. Y.,j1976, R. E.
45. Wakim. K. GI: P h y r i d o g i d efft{u;of wugc. In Mu&,
iri.Npu¡atbn a g frac:¡?
New Haven, b n n . , 1960, $. Li< D aad E.
e,
Kkk+~fI?ubli rhcr.
cupatioii therapy. 1.n Hmtlbmk : :I.
medicini and rt~h~biliution, P i ,I I I
l%6, W.E, Saviulen Co.
53. Downer, A. H.: Phpicil therap! 8 . 5 1 I , '
Springñeld, Ill., 1974, Charles I
1.1 I I
Publisher.
54- R o d , J. C., and Reine?, S.: 1
IF i l ,
-tic
ippiirrtus. In Elecimdiagn~s~.I I t l .
tmmyosiapby, ed. 2, New Hsv, I I I
1961, S. Licht and E. Licht Publi i :
55.. Barnes, 11. B.: Thermography a n i
1 ti
application, Ann. N. Y.A u d . Sc;. I I: I ,
'I.
~
l%4.
pp. 204-232.
51. Harris, R.: Tjction. In
~
52. Martin, G. M.i Racribiig ph+#
bpipula-
M o+
,:I
,;
!
:.
.,
31
I.
56. Licht, S.: !&ctrical skin r e & ~ n c < I I :,i
trodiignmii and c l c c t m y o ~ ;1'~ ~ ':# >
Haven, COM., 1961, S. Licht aii i . i c I
Putdirhr, pp. 412422.
57. Roa, A. S., Ellison, C. W., Mer, i i L V
and Tourtdloite, W. W.: Critrr: . ' > I ' '!
clinical du@wair ai multiple rcleto' i:i I h r
A d . Nruml. 28:(8):21, 1976.
58. Duwdt. J. E., and BommtM, E.: P.%! i
of myurhe& gravis by n e w ai:n I! s. ~ 1 8
N. Y. Arad. Sci. 274:174-188, 1973.
59. GilhtI, R. W.: Nenr conduction: >i: 1 i
I I
smw.0~. In Elcctrodiignoli and ck, :':E,I >
nphy. New Haven, Conn., 1961, !
i:: I
and E. Licht Pubkhiher, pp. 385-411
60. h i a c e , R. E., and Mcyerr, S I. I ? - '
conduction and synaptic t r m s m S E in 1 I
Downey, J. A., and Darling, R. C , :d < I :
Phyiblo~icalheir ai rehabilitation r .i i 1
Phillddphk, 1971, W. B. Siunde- (1 D
61. Goodgdd, J., and Ehenitein, A . : ! "I ! I
duntion curve. In Electrodiagnosis 11 I, I.,
muscular distases, Baltimore, 1972, 1' ( I \ i
I ¡ ¡ B Wilkins Co., pp. 28-30.
I.
CHAPTER 29
Th
a.
b.
REHABILITATION OF PATIENT WITH
PERIPHERAL VASCULAR DISEASE
c.
2. Eli
a.
3.
b.
hí
a.
b.
c.
d.
e.
The term peripheral vascular dixases, as
refund to in this discussion, will encompass
diseases of the arteries, veins, and lymph vessels in the extremities. The d i m e processes
include not only pathologic conditions within
the confines of these vnrels but also many
conditions due to reflex disturbances in these
vessels secondary to sympathetic, parasympathetic, and spinal cord influences. It should
be emphasized that this section is not so complete as it might be but will include those
diseases in which rehabilitation technics have
been or are still employed by some physicians.
I t is quite apparent that the'entire complexion of care of obliterative arterial diseases has been radically altered by the success of direct definitive surgical treatment,
somewhat eclipsing medical and physical
measures.
The study of peripheral vascular disease
requires essentially the same technics that
one generally employs in internal medicine:
history, physical examination, and special
evaluation technics. There are, however, certain basic aspects of this group of dixases
that require special emphasis in the examination and that ma>- be elicited only by a
sound history. It is therefore most imperative
that a thorough knowledge of the classification of these diseases be known.
EXAMINATION
The physical examination in peripheral
vascular disease must be thorough and general prior to concentration on the affected
area. The importance of obtaining a history
of trauma, diabetes, and previous venous
thrombotic or ca?diac diseases is self-evident.
594
Certainly the knowledge that a malignancy
with metasiases exists in a patient with recurrent venous thrombosis that does not respond to anticoagulants is a potent factor
governing further therapeutic endeavor. The
physical findings of a mitral valvular lesion
associated with auricular fibrillation in a patient with evidence of acute arterial occlusion may be of paramount importance in
establishing the etiologic basis of the presenting symptoms.
Much information may be gained for the
specific diagnosis of peripheral vascular disease and for the clinical evaluation of the
condition by means of tests designed to measure some physiologic function or physiologic
capacity. In addition, specific measurements
will enable one to evaluate objectively the
response to therapy. Accordingly the use of
Mays' test for intermittent claudication, oscillometric readings, temperature recordings,
and various tests for vasomotor stability
should be employed when indicated. Angiography and venography are frequently used;
infrared photography, plethysmography, and
the Doppler ultrasound flowmeter may also
be used.
The treatment of peripheral vascular disease extends far beyond the confines of rehabilitation medicine, but care for these disorders may be aided with the use of certain
technics.
TREATMENT
The scope of treatnient of peripheral vascular disorders within the discipline of rehabilitation medicine may be outlined as follows:
4.
f.
TI
a.
b.
5. Pr
a.
b.
6.
C<
Therm'
HYP~
peated
for re1
of col1
tive of
and, t<
thromt
dures
degree
blood
bolizat
disease
of noa
Due
most e
tion. 'I
an inc
dent i
tabolit
rliemii
additic
blood
about
tempe
by he:
is base
Diri
ant h
dectri
tically contmlled heat cra#les,
rsion beat of diathermy !and
chployment Of local heat alwayq inof a cakulated risk. me
)ñective beating of &e tissues urlporni 5 at
1times +ter
than the mcubolic eñeq so
t, witb even moderate heating, then U
?e
V0i.a~z+umption
lyreat dajger of bur+
Maintenance of +afe
M a n tgnprature with application of i + d
the heat-absorbing cap&ity
b l & l Row. Occhuive apeIdes!
this function of b e
jrcullrr +tun, and Lht quantity of h u t ic
to accumu+e to &e critical pibt
tisuC (kruuction. !In addition to t h h n .
dilcquate fhiptionof heat, the mneolnitwt
of
meUbOl¡c@procnram y be dqe*ow by! compouadimg the oxygen req+
den@ of ;Llrcady M O ~ C tissue, as well astby
i+ng:the
10cll accumulation oí marWlic end products.
! Indkcdbat Appli(ltion of indirect hehtevokd a gcnernliH refkx vasodilatiqn,
e extentiof which is.dcpcndent on the deof +onstr¡ctidn
and artepial b l a
decarbpensption. An application of the
be exdmplified by use of. a
the awomen for 20 to 50
d a i m w 3 0 finduction of vasp
the 11utremi&aS. T$e
Thormothwapy
Hypoithormla.
puted epiaodler
for relief of
tive of treatmefit in
thrombosis. lht
I.
most efficient mepos of
ccting vam+iad
.'&bmbotic idisuu.
tion. The local Ne of te perature resiilts io
yp.fhojrnio. It is ohiy retcntly that gedan increase of cchiar ac ivity with an inch
body @pothernia or "anfñeial hibemaof conccnt ation of acid m i
dent inctiop" has gained w e l l i d m w d rroognitim
tabolites and himmine-li substanm. b a s
in :its use h c a r d i o v a + w
nauroiaglc
chemical agents are pote t vlrodiiatow. Iq
s
v Its buc in les dhmatic medical cow
addition the rise of the
pcrature d thq
dit, ns has pot as p t barn fully exploited.
blood stimulates medullap ynters M, brin4
In acute *erial occlúsion the applicatioa
about d e x vdilaeiony t n c m e of thq
of trypoth&ic
measuq can be readily s u p
temperature and blood fi+ in an wttrimity
po+ed on tbe theoretic basis of equating tis.
heating of some remot pan of the &XI
!-metaboflc requiremqnts with the dimin.
sücj
is based on this principle f mtkx rrspchse.
b k d Euppl. Praciically, however. this
Direct heat may be app ed by uy of nidipcutic epproach Ras not been carefully
ant heat lamp, conduc on heating with, d*d
a n d b daerving. of further study. It
electric pads, hot-water bottles and fomtnuis at least udwmlly acctpied that the appli-
i
.
I
596 Rehabililniion medicine
cation of heat is unphysiologic and most ill
advised.
Actual refrigeration of a limb has proved
to be extremely useful in securing control of
a situation wherein irreversible and extensive
ischemic changes dictate ablation but where
some other medical consideration mitigates
against proceeding immediately. Packing of
the limb distal to the point of contemptaied
amputation is usually followed by rapid improvement of the patient, subsidence of toxic
symptoms, drop of temperature, and abatement of pain. Distal icing is not associated
with disturbance of wound-edge healing and
secondary wound infection.
Hypothermic studies in the treatment of
local tumors have established that cold is
effective in diminishing edema and effusion
and in relieving pain. These responses appear
to be operative in the use of ice bags applied
to the calf and thigh by some physicians in
the treatment of patients with thrombophlebitis and venous thrombosis. Inñammation, induration, edema, and pain appear to
be rapidly controlled, so that cold appears
to be much efficacious than hot fomentations. An occasional patient treated in this
manner may find the cold intolerable so that
its application must be terminated. Such an
individual, however. is the one who manifests
unusual degrees of secondary vasospasm that
responds best to paravertebral sympathetic
nervounystem blocks.
Allernaling lemperalures. The use of
contrast water baths, in which the patient
alternately submerges his feet in warm and
cold water. is now employed to little advantage in the treatment of vascular disorders.
With arterial problems, for example, the
constrictor of the immersion into cold far
outweighs the supposed beneficial effects of
alternating the raliber of the vessels.
In the patient allergic to cold, however' it
is sometimes beneficial to effect gradual desensitization by daily treatments with immersion of the nfferted extremity into water that
is progressively rooled.
Electrotheropy
Muscle siimulolion. Stimulation of muscle
with electric current finds no place in the
treatment of vascular disorden. Some year3
ago, however, an electrostimulator designecl
to prevent venous thrombosis following sur.
gery had been introduced. In this approach
the calves and thighs of patients on th,:
operating table were subjected to rhythmic:
contractions in an attempt to improve venou:j
blood flow and prevent the static influences
favoring venous thrombosis. The apparatus
has not found \r-idespreadapplication.
Iontophoresis. Ion transfer with histaminit
and methacholine (Mecholyl), when carried
out with due precautions, is a safe, effective
means of obtaining local vasodilatation in
both arterial and venous disease. Ulcerations,
indolent to other forms of treatment, may
exhibit remarkable response to direct ionto.
phoresis with methacholine. This type of
treatment appears to be particularly helpful
in the care of patients with vasospastic disorden, such as Raynaud's disease, with ulcerations of the distal ends of the digits.
Mechanotherapy
In general, mechanical modalities have
proved of little value in the treatment of peripheral vascular diseases. Briefly they may
be reviewed as foll0u.s.
lniermiileni venous occlusion. In this
procedure occluding cuffs are applied to the
extremity under a specific pressure for a fixed
interval; the pressure is then released for a
short relaxation period. The physiologic basis
of the treatment U considered to be an application of the observation that venous occlusion is followed by a priod of reactive
hyperemia. Several instruments am available
in which alternating periods of venous congestion and relaxation are intermittently produced and for which sometimes excessive
claims of beneficial results in treatment of
ischemic arterial disease have been made. In
general. however, observed results are not
impressive and have not withstood careful
scrutiny of blood flow changes with plethysmographic methods. The recommended
rourse of therapy is lengthy, and the g o d
clinical results reported do not take cognizance of the natural forces bidding up collateral channels.
Pressure-suciion boot. The pa\.ex boot,
anotha
cise, P
suctio
ity, w
.
ber.
tempe
ulcera
with
no re
poses
antiqi
Os1
the o!
vice
exerci
the p
peutii
fit in
oscill;
seem
helps
seen
maini
deper
from
surfa0
the ri
Va
ratus
fourti
iiiflat
fashi,
wave
erall)
Cuff
trolle
in cei
insufl
the t
ing f
view
to th
ment
chr01
SY.
ployr
inect
cular
dure
cardi
plied
*
another example of passive mechanical exer.
cise, employs the application of intermittent
suction and pressure to the involved extremity, which is enclosed in a treatment chamber. Although early reports noted rise in
temperature and beneficial effects on the
ulcerations and ischemic neuritis of patients
with occlusive disorders, this procedure has
no real proved value and for practical purposes has been relegated to therapeutic
antiquity.
Oscilloiing bed. For practical purposes
the oscillating bed may be described as a device that passively administers Buerger's
exercises to the recumbent patient. Again,
the procedure is far from proved in thcrapeutic value but appears to be of some benefit in relieving ischemic pain. The continuous
oscillating movement of the bed does at least
Seem to have some sedative effect and also
helps control the severe edema frequently
seen in patients with arterial disease who
maintain the limb in a constant position of
dependency in an attempt to obtain relief
from discomfort. Reports concerning rise of
surface temperature of the limb after use of
the rocking bed have been at great variance.
Vosopneumaiic compression. The apparatus for this procedure consists of a series of
fourteen rubber cuffs that are progressively
inflated in either centrifugal or centripetal
fashion in an attempt to effect a pressure
wave traveling toward the heart or periph..erally
.
toward the distal end of the extremity.
Cuff pressure and compression rate are con,t$led.
The apparatus has been employed
in centrifugal fashion in patients with arterial
~i
i&ufficiency and in a centripetal direction in
the treatment of patients with edema resulting from chronic venous insufficiency. A review of results neported lends some support
to the emplo:.ment of the apparatus in treatment designed to reduce edema secondary to
chronic ilmphatic and venous obstruction.
3yncardial morsoge. The instrument employed in this procedure represents another
mechanical device for the treatment of varcular disorders. I n application oí the procedure the ventricular complex of the electrocardiogram is detected from electrodes applied to both arms. From the involved ex-
-
~
treinity, to which an inflatable CURhas been
applied, an arterial pressure curve is picked
up. I n an attempt to augment peripheral
flow,' a cuff, complete with a n electronic delay, is assembled on the patient. The time at
which the cuff inflates is related to the ventricular complex, as well as the descending
limb of the arterial pulse curve, Although
several investigators who used such objective
means as pressure study in vessels distal to
the site of cuff application and plethysmography have reported little physiologic effect,
other investigators in the United States and
Europe have rendered enthusiastic empirical
reports.
Massage. Massage is of little or no value
in arterial disease, although light stroking or
d a t i v e massage brings about a reflex vasodilatation and increased cutaneous blood
flow. Heavier massage maneuvers should not
be employed, since they may represent a form
of repeated small trauma of sufficient additive magnitude to precipitate destructive skin
changes. It may be noted that employment
of vibrator). devices falls into the same category, even though thermometric and radioactive sodium clearance increases have been
demonstrated in the local area of application.
Recause of the danger of dislodgment of
loosely adherent thrombi, with secondary
embolic complications, massage is strictly interdicted in patients with acute venous
thrombosis. However, the late complications
of this disease (indolent edema, induration,
eczema, and ulceration) may be benefited
by the judicious application of massage as
part of an overall plan to combat the effects
of venous insufficiency. In 1939 Disgaard of
Denmark introduced an ambulatory treatment for patients with indurated legs, which
combines a program of elevation, massage,
bandaging. and exercise. Results reported in
the United Stales and in Britain lend support to the efficacy of the program and indicate the desirability of more extensive application.
Therapeutic exercises
Buerger's exercises. I n these postural erercises the limbs are elevated until blanched
598
Rehobilitation medicine
and then placed in a dependent positioii until beginning rubor. An interval of rest follows. This alternating filling and emptying of
the vessels theoretically increases the arterial
blood flow. The procedure is widely employed but is of highly questionable value,
especially in the dubious light cast by carefully controlled studies on clearance of radioactive sodium from the calves of patients performing this exercise.
Theropeufic wolking. Therapeutic exercises in the form of controlled walking represent a most physiologic approach to treatment of arterial occlusive discase, provided
that trophic lesions are not present. The latter qualification itself may eventually have
to be altered in the light of some recent
favorable reports on the use of exercise as a
means of promoting collateral circulation in
patients with limited gangrenous lesions.
Walking places a physiologic demand on the
muscles of the extremities that can be accommodated only by the appearance of collateral blood channels. The patient with
intermittent claudication should be encouraged to walk at a slower but regular cadence,
up to the point of pain. It does not appear
feasible to force walking beyond this point.
since the vasoconstriction incident to increased pain is a detrimental factor. Rather
the patient should be instructed to accept
the rest period required for subsidence oí discomfort and then to resume ambulation. Collateral studies of radioactive sodium clearance from the calf musculature, referred to
in regard to Buerger's exercises, were also carried out following periods of active use of
the limb. The preponderance of evidence
points to greater clearance and. therefore,
greater blood flow following anibulation and
active exercise.
Piophylactic maasurer
General. The prophylactic measures related to the care of patients with arterial diseases should be considered carefully. since
approximately 307; of patients reporting to
the department with potentially serious conditions have self-inflicted lesions caused by
improper shoring. misapplication of medica-
tions, injudicious podiatric rare, and generally poor hygienic measures. Enumeration of
the precautions to be observed by such patients may be found iri one form or another
in the various texts on vascular disease, but
because of their importance, they bear repetition. Prophylactic measures advised at the
Institute of Rehabilitation Medicine are given
in Chart 22. Because of the high incidence
of trophic lesions initiated by the use of improper footgear, it is pertinent to discuss this
measure in somewhat greater detail.
Footgear. Footgear, by definition, includes
all coverings of the foot, both hose and shoes.
Hose. T h e arteriosclerotic patient should
use lisle hose, fitted two or three sizes larger
than the shoe and manufactured without
constricting elastic tops. Lisle is porous and
absorbent. Hose manufactured with squaredoff toes are most desirable, to avoid constriction of the terminal portion of the digits and
to avoid the tendency toward ingrown nail
growth. Stretch hose and nylon do not meet
these criteria and should not be worn.
Shoes. There is no compromise for comfort, so that shoes must fit properly immediately; esthetics are secondary. Shoe size is
determined by a fit that permits enough
room beyond the toes (approximately i inch
beyond the great toe) on both sides to allow
for spread on weight bearing and rmm over
the dorsum to avoid injury by pressure and
abrasion. It seems most practical to fit shoes
in the early evening to allow for the even
slight edema that most vascular patients
exhibit. The sole of the shoe should be made
of leather rather than rubber or a composition material. since the latter materials are
poor heat conducton and increase perspiring.
New shoes should not be worn for more
than from 1 to 3 hours a day for the first
week. The preferable style is an oxford
manufactured from either kangaroo or Vici
kid leathers. both of which are supple and
poroiis. permitting ventilation and avoidance
of hyperhidrosis. Patients with hallux valgus
should be fittrd with bunion-last shoes that
are designed with a specific pocket to accommodate the deformity of the toes.
The repair of shoes of these patients is
.
Rehabilitution
o/
patient with peripheral uarcular disease
mer-
?d
. . -8n
of
.??
,
CHART 22
such par n"7ther
1 p ~ ! but
:=r repeti-
PERIPHERAL VASCULAR SERVICE
,*.
a
the
2ri :¡\-en
INSTITUTE
O F R E H A B I L I T A T I O N MEDICINE
New Y& Univmity uedierl Ccnta
IiiiOUence
:<? of im,.XL
,
..
this
CARE OF THE FEET AND GENERAL INSTRUCTIONS
includes
:id "-m.
-,~.
ould
.,-
larger
dhout
i:oi
and
qYiared.-qf-tricand
-\un nail
.es
-90
:lot meet
*.-
iom*_
:mmedi+e is
7:
>ugh
'Tinch
o-~llon
~.31 over
~ 2 %and
ñt
shoes
:n even
.-ients
:xmade
:rrrposi): : !
i arc
1. Wash feet u& night with fiesoap and w u m water; dry gently by patting
with clean wft cloth
2. Apply XI percent rubbing alcohol and allow feet to dry thoroughly; then
apply liberal amount of petml.tum, toilet i a d i n , or coconut oil and gently
m-e
skin oí feet
S. Airar, keep f a t mmi; wear wookn sock or wd-lincd hin winter and
cotton socks in warm weather; wear clean pair of sock each day
4. Wur bsst-iittiugbcdiodo at nighht; a y hot-water bottle or electric pad to
abdomen; never put either d thac d i m t y to feet az lega
'p'
5. Wear shm of aoft luther without box t a r ; bc particuhrly careful not too
tight
6. Cut toenail atnight acmn and only when in very good light and only after
feet hive been clealucd thoroughly
7. Do not cut corns or callura; ye podiatrist
8. Do not wear circular garten
.
I
--~..spiring.
L .
:'r,more
first
ii
~
vníord
or Vici
: :Y" and
. ..
,. ance
1-
': valgus
I>--
that
rom-
..:::iLnts
..
.I
is
9.
D o dot sit with lqp crosxd
10. Ov&pping
t o a and cxcarivc penpiration of toes should be corrected by
inserting lamb's wod between than
11. Never uac tincture of iodine, Lytol, cresol, carbolic acid, or other strong antiseptic drugx on feet
12. Call doctor's attention to appearance of troublcorn, ingrowing toenail,
bunionr, or ullusa; a b wra, m h o , or blisten n feet or legs
13. f i t plenty of green vegetables and fruits in a well-balanced diet, unless ordered
to follow a special diet
14. D o not m u tohacco in any form
599
600
Rehabilitation medicine
also quite important, since reconstruction
may alter the fit. Resoling, for example, ordinarily results in narrowing of the shoe because the leather is drawn in when the new
sole is stitched on. Ideal conditions exist
when the shoe is returned to the factory and
repaired on the original last.
Comprehensive rehabilifafion measures
The principies of rehabilitation of the patient with vascular disease vary only in
minutiae from the general concept of care oí
patients with disabilities.
Arteriosclerotic patients with compensated
arterial blood supplies usually are able to
pursue a normal occupation limited in major
aspect to avoidance of exposure to conditions
precipitating intermittent claudication or
trophic disturbance. For example, a patient
employed as a waiter in a bury restaurant
required vocational reexploration and counseling because of continuous o w t of intermittent claudication. A young police officer
with thromboangiitis obliterans required
transfer to an indoor assignment when it was
noted that he suffered onset of extreme vasoconstrictor phenomena when exposed to
inclement weather. This type of patient, as
well as one with chronic venous insufficiency
and vasospastic diseases, represents primarily
vocational problems so that normal gainful
employment may be m;.iritained or restored
within the restrictions o1 i.he physical defect.
The amputee, however, has a special problem that has been discussed previously. ?he
psychologic and social adjustment of the latter patient to mutilatirg surgery and the
fitting and adaptation tu the use of a prosthesis are at least as important in rchabilitation care as arc vocation.4 considerations.
CHI
-.
Rl
W
REFERENCES
Allen, E. V., Barker, N. W., and Himr, E. A,:
Periphenl vascular direasis, Philadclphin, 1955,
W. B. Saunden Ca.
Fay, T., and Smith, L. W. Temperature facton
in cincer and embryonal cell growth, J.A.M.A.
119:653, 1939.
Freeman, N. E.: Influence
tcmprature on the
development of gangrene in peripheral vascular
diseases, Arch. Surg. 40326, 1940.
Lewis, T.: Vascular dilordcn of the limbs, New
York. 1936, The Macmilhm Co.
Knmer, D. W . : Pcripherxl vascular di-,
Philadelphia, 1948, F. A. Davis Co.
Smuelr, S.: Diagnorir and ireatment of vascular
disorders, Biltimarr, 195ri, T h e Williams &
Wilkins Co.
Wnkim, K. C., and othcn: The influtnct of
ryncirdiil musage on thc: p n p h c n l circulation, Arch. Phyr. Med. Rehabil. 97538, 1956.
Wisham, L. H., Abnmron, ,i. A,, and Ebel, A,:
Value of exercise in periplieral artend diseare,
J.A.M.A. 159:10, 1953.
Wright, I. S.: Vascular diseases in clinical practice,
Chicago, 1952, Year B w k Publishers, Inc.
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g r d o ae f i e x i m i d d a a ,
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en materlaLes rlo*ogicos.
y d e aesilie...o
&
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c60rifw0
ai
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p r o y e c t o corista u e dos p a r t e s ;
eb
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para r a s t r a e o t r a T ~ un
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p r o ~ r a m a o r QB temperatura en
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para yenerar una r e f e r e n o i a grana
poteiiciomatroe
ae temper-tu-.
C i r c u i t w i a ~ e c t r o . A i c 8& .
L. a i s & f o o m j e t i v o a e er c i r c u i t o B e ControA e s & a si&:
a ) proauclr una
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forma de una ramp& & i n e a ~OQU un rango proijrambLe d e r i m y caida
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ñ&Y&:XdNNCIA 'I m''
A p l i c a c i o n e s de l a s Imagenes de NMR en Hipertermia: Una Evaluación
de e l P a t e n c i a l de L o c a l i z a c i ó n de T e J i d o s C a l i e n t e s en N o n i t o r e o
de Temperatura N o i n v a s i v a .
Sumari o.
-
La A p l i c a c i ó n de l a Besonancia Magnética N u c l e a r
(NMR) en
t r e s Dimensiones.
Para monitoreo de temperatura n o i v a s i v a como también e l calentamieri
t o de t e j i d o son d i c u t i d o s . Aunque e l d e l i b e r a d o uso de c a l o r conv e n c i o n a l en imagenes de NMR e s i n s i g n i f i c a n t e , l o s hases f i s i c o s
para transferir c a , l o r son r e v i s a d o s y e l p o t e n c i a l de incremento e s
mostrado para depender en ambos, e l campo esta.ticomagnetico y e l
tiempo de r e l a j a m i e n t o l o n g i t u d i n a l , ( T I 1.
De l a d i s c u c i ó n de l a s bases f1sica.s de l a tendencia. de temperat u r a d e l l o n g i t u d i n a l (1'1) y t r a n s v e r s a l (T2) en l o s tiempos de rel a j a m i e n t o , e s t o e s que T I puede s e r un i n d i c a d o r mas s e n s i t i v o que
T2. L o s experimentos p r e l i m i n a d e s en e l á r e a de monitoreo r e g i o n a l
de temperatura en sangre y agua, son ejemplos que i n d i c a n que l o s
cnmbios cte temperatura puecen s e r monitoreados. A1 comercio a. t r a v e s d e l e s p a c i o y la r e s o l u c i ó n temporal, a s i t a n b i é n la. e x a c t i t u d
y l a p r e s i c i ó n de d i c h a s m e d i c i o n e s i l i s t a c l a r o que muchas p r o b l e m a s de t e c n i c a s pueden s e r superadms con e l NMR y pueden s e r usados
p a r a monitoreo de temperatura en h i p e r t e r m i a .
-
.~
.
-.
.
.
...,
,
i n t r o au c c i 5' ,.
biempre que la. n a t u r a l e z a de l a resonancia magmetica n u c l e a r
(NMX), pueue s e r usada y a t e n d i d a en e l e s t u u i o ae l a . e s t r u c t u r a
e l e m e n t a l y m o l e c u l a r de decadas (173), uno en l o s 10 años f u e at e n d i d o para s e r usado con 1Ul~lH para c u a n t i f i c a r l a d i s t r i b u c i ó n
e s p a c i a l (4,t>). Porque l o s mecanismos ae r e l a j a c i ó n ae l o s mornent o s magnéticos n u c l e a r e s en campos m a g n é t i c i s e s t a t i c o s envuelven
i n t e r a , c c i o n e s t e r m a l e s con e l suso dicho ambiente, e s t o e s de espsc i a 1 importancia para determinar e l p o t e n c i a l d e a p l i c a c i ó n de l a s
imagenes de NMH para h i p e r t e r m i a . Donde l a primera. propuesta. d e est e p a p e l e:> para r e v i s a r y d i s c u t i r e l p o t e n c i a l de a.plicaciÓn de
ims.genes de NUX n o i n v a s i v a s , monitoreo ue temperaturp, l o c a l i z a . d a ,
algunos comentprios i n i c i a l e s pueden s e r hechos c o n c e r n i e n t e s a l
p o t e n c i a l ue l o s d a t o s usados- en NMR Pars? hipertermia,. S i e p r e que
e s mostmdo que los paremetros f i s i c o s meuiaoü con NMR son independ i e n t e s de la temperatura, e s t o e s n e s e s a r i o para determinar s í 'uno
de e s o s parametros pueae s e r medido con s u f i c i e n t e agudez y p r e c i
siÓn para iliediciones de temperatura, n o i v a s i v a s . Algunos r e s u l t a d o s
p r e e l i m i n a r e s en mediciones ue temperatura n o i v a s i v a son usados(ó).
-
Conclusiones; &s e v i d e n t e que de e s t a s d i s c u c i o n e s , que l a l o c a , i i z a c i ó n de c a l e n t a m i e n t o con NKH no e s p r á c t i c a , usando mediciones
ae temperatura r e g i o n a l con Óptimo seguimiento de imagenes de KMR,
l a c u a l como e s une. siiiiple t é c n i c a s e n s i t i v a de punto, puede no s e r
muy p r á c t i c a .
Porque be usos r e l a t i v o s a cambios de agua extra-e i n t r a c e l u l a r , y
porque T2 en e l agua d e l t e j i d o e s cercano a un oráen de magnitud
mas c o r t o que TL, e s t o e s e x p e c t a t i v o y a que TI puede s e r un i n d i c a d o r de temperatura mas s e n s i t i v a que T2.
Porque l a complegidad del, aparpto de imagenes de NMR y su uso r e l a ciona.do con l a s e ñ a l independiente de v a s e l i n e e x i s t e n t e . E s t o i m p l i c a que l a r e l a c i ó n sefia.3. r u i d o y e l s e n s i t i v o r e s u l t a d o de tem
peratura. pueda v a r i a r en ur.a p r o p o r c i ó n d i r e c t a de l a poderasa s e ñ a l
La s e n s i t i v a . temperatura puede m e j o r a r con e l aumento de l a fuerza.
en e l campo, l a meciición de volumenes grandes y v a l o r a r l a s multip l e s mediciones.
S e v e r a s preguntas pueden no s e r c o n t e s t a d a s y pueden s e r d i r e c c i g
nadas p w ~ l. a termometría no i n v a s i v a usando NMH puede s e r una ap l i c a c i ó n p r á c t i c a . La v a r i a b i l i d a d en l a tempieratura s e n s i t i v a de
10s v a r i o s t e j i d o s en d i f e r e n t e s i n a i v i d u o s puede s e r mostrada.
Los e f e c t o s de tiempo de r e l a j w i ó n en l a s r e s p u e s t a s f i s i o l o g i o a s
p a r a calentsuniento (como el. incremento de f l u i d o sanguíneo), e s t o
e s e v i d e n t e en algunos e f e c t o s f i s i o 1 Ó g i c o s : ' p u e d e n o c u r r i r en v i v o
y puede s e r e s t u d i a d o en v i v o . La p o s i b i l i d a d de anomalias c e r c a
nas a l a s temperaturas en h i p e r t e r m i a pueden s e r demostradas ( 2 4 )
y pueaen s e r supervisaaas. Es e v i d e n t e que en muchos años f u e r o n
n e c e s a r i o s p a r a responder a n t e s e s a s preguntas.
-
-
Una Revisión de l o s Metodos de Inducción kagnética para Tratamientos de Hipertermia en Cancer.
.-
bario
L o s metodos de inducción magnética para predecir poder de absor
ciÓn en tejidos son usados para llevar a cabo l a hipertermia en
tumores en l a terapia experimental de cancer. La distribución de
l o s campos electromagnéticos y asociado con l o s rangos de absor
ciÓn concentricos en tejidos (SAH), el desplome de l a abertura coa
xial de corrientes de enrollamiento son discutudas. Aplicación de
l a ecuacijn de transferencia de calor usada por S a en l a predec
ciÓn de la. distribución de l o s campos en e l tejido normal y elevación tie l a . temperatura en el intratumor. La corroboración de esas
predicciones por fantasmas, en cuerpos humanos y animales e s para
confimar l a tranferencia de biocalor em el modelo en l a elevación
de esos metodos de hipertermia. El tamzfio del tumor y deformación
son precauciones buenas que se usan en las técnicas de inducción
magnética de calentamiento, y s o n revisadas, basadas en las evi
dencias pribadas.
-
-
Introducción.dl uso iiioderno .de los metodos de inducción para elevar l a temperatura ae l o s tejidos es revisada en este artículo.
dn particular l a distribución de l o s campos electromagnéticos producidos en un lugar paticular y usado en la terapia de hipertermia
en cancer.
La interacción de esos campos con tejido para un resulptadm espe
cifíco en l o s rangos de absorción de energía ( S A E ) , y el resultado
de l a elevación de la temperatura en l o s tejidos normales y turno,.res es calcula,docon la ecuación de transferencia de bicalor, que
nosotros consideramos. Un pequeño sumario cie experiencias en clíni
--
-
ca y laboratorio son dados como un medio para corroborar
l a predi
-
cción de l a distribución termal.
Aplicación Clinica y Observaciones.
-
Un número de documentos en clínica humana son usados para descri
bir el tejido normal y l a temperatura en el intratumor, la toleran
-
cia del paciente, toxicidad, y respuesta asociada al tumor con l o s
tratamientos de inducción magnética (metodos (3b-47)). Las diferentes relaciones en l a seleccijn de pacientes, sitio tratado, y va?:'.-
,
~
*
*
y
-
-
. .
r i a c i ó n en. l a combinación de q u i m i o t e r a p i a y/o r a d i a c i ó n con h i
p e r t e r m i a , e s t o s r e p o r t e s impiden una simple comparación de l o s d a
t o s de respuesta.
E1 d a t o termometrico también e s d i f i c i l de comparar porque e l l a r go g r a d i e n t e de temperatura i n t r a t u m o r a l e x i s t e y que v a r i a con e l
tamaño d e l tumor, de fonmación, grado de p e r f u s i ó n sanguínea.
Limitando l o s e j e m p l o s de temperatura podemos i n c u r r i r en l a v a l o r a c i ó n del. r a n g o de tenipere-turne i n t r a t u m o r a l e s formadas y una m í nima temperatura tomada \ 4 7 ) .
-
He sumen.
f o s estud.ios t e ó r i c o s de SM..,y l a d i s t r i b u c i ó n de temperatura obt e n i d a con v a r i o s metodos de inducción magnética e j e c u t a d o s en h i
p e r t e r m i a son r e v i s a d o s . Los s o f i s t i c a d o s modelos t i e n e n r e s u l t a d o s
que también pueden a p l i c a r s e p a r a e l e s t u d i o de o t r a s modalidades
de c a l e n t a m i e n t o .
Un gran número de e x p e r i e n c i a s en l a c l í n i c a humana son confirmad a s en l a p r e d i c c i ó n d e l modelo y sus s u p o s i c i o n e s d e l concepto de
e x t e n s i ó n en l a a p l i c a c i ó n de modelos numericos para l a p l a n e a c i ó n
de t r a t a m i e n t o s c l í n i c o s y d o s i m e t r i a t e r m a i , como siempre e s d e s
c r i t o en e l t e j i d o .
La mas apropiada a p l i c a c i ó n de l o s metodos de i n d u c c i ó n magnética
apErecen para s e r e l t s a h m i e n t o en tumores mas e x t e r i o r e s , 6-7cm.
d e l t e j i d o en s i t i o s subdiagramaticos, con c o r r i e n t e s c o n c e n t r i c a s .
La l i m i t a c i ó n a e l o s metodos de inducción p a r a tra.tamientos en tumores i n t r a t o r a c i c o s son menores, p e r o b i e n d e f i n i d o s c l i n i c a m e n t e .
Al volumen s u b s t a n c i a l de d i c h o s tumores puede s e r e l e v a d o a menos
de 42 C , y en ca.sos de tumores con diametros de menos de 10 cm.
Pequeños e n r o l l a m i e n t o s empaquetados son un medio e f e c t i v r h en e l
c a l e n t a m i e n t o de pequeñas s u p e r f i c i e s con tumores con dimensiones
mayores que 4cm. en l a s u p e r f i c i e mas s e v e r a a c e n t i m e t r o s a e l t e j i d o d e l cuerpo. PL diametro mayor ( e s menor que 20 cm.) en co
r r i e r i t e s de e n r o l l a m i e n t o pueden p r o d u c i r un a l t o SARy d a r d e f o r mación en l a s c o r r i e n t e s c o n c e n t r i c a s . Bsos e n r o l l a m i e n t o s produ
c e n un t o r o j d e en l a d i s t r i b u c i ó n d e l SUR, que e s complementario y
que e s producido P o r c o r r i e n t e s de e n r o l l a m i e n t o , e l s i t i o de formrción y e l tama.ño d e l tumor apropiadamente tr-t
R ado con c o r r i e n t e
de e r i r o l l a m i e n t o pueden s e r d e f i n i d a s .
-
-
-
I
.
..^
...
r.
BIBLIOGRAFIA.
. ,.
.
I
,
.
I
.I .
agrnta such as radiation, chrmotherap). and heat (Elkind ~ n d
Uhitniore [ I 21). During the last two decades. radiobiologists
in particular carefully studied the effects of hyperthermia on
normal and tumor cells since they were familiar with the use
o f in vitro assay systems for measuring effects of radiation and
drugs. The results of these cell survival studies in the 1970's
showed that cessation of ceU division, defined as mitotic death
or cell killing, was attained i f cells were exposed t o temperatures in excess of approximately 40'C for time periods of 30
min or more (1131 and Fig. I). 1nthisfigure.thesurvivingfraction o f the heated ceUs is plotted on the ordinate as a function
of the time the cells were held at a specific temperature. Note
that above about 42.S'c, small differences in temperature, on
the order o f tenths o f 1 C, resulted in significant increases in
cell killing such that dn increase o f I o C corresponded t o an
approximate halving of the exposure time necessary to produce
an equivalent level o f cell killing. These results signaled t o the Fig. 1. Cell survival curves, from Dewey et al. 1131. Reprinted by
clinician and engineer the importance for measuring accurately
mission The surviving fraction o f CCUS grown in a medium at ,
w
the temperatures produced by hyperthermia systems and the
ticulnr temperature ii plotted on the ordinate. The absclm
need for producing precise levels of temperature throughout
length o f time the ccllr have becn exposcd lo the specified tempera
tumors.
Although the exact details o f mechanisms responsible for the
cell killine-b v,hvoerthermia are not known. studies continue to
.~ much ImS effective In terms o f additional cell kill if it is
suggest that the mechanisms include effect; on cell membranes to0 soon after the first heat dose. The effect is produ
and may take Over 72 h t o decay before cell ~enutivity
and cell metabolism including intermitosis death [ 3 ] , which
are somewhat different than those p r o c f f ~responsible
~~
for returns to original kvels. This thermotolerance may
radiation or dmg-induced cell killing (these latter modalities important factor t o consider in the design of clinical p
hyperthermia will most likely be delivered in
have demonstrated specific damage t o DNA). perhaps
fractions.
importantly, several environmenta¡ factors have been identified
The most important biologi
as conditions which will significantly alter the response of ceUs
temperature
distributions achie
t o hyperthermia or which suggest a rationale for combining
hyperthermia with radiation. F o r example, h y p o u a (decreased ing normal tissue is blood flow.
widely in normal tissues from
oxygen concentrations) conveys radioresistance io cells but
' min in fat t o values as high as
hypoxic cells appear to be as heat sensitive as are well oxyFurthermore,
these values var
genated cells. Cells in the DNA synthesis (S.phase) of the cell
life cycle are most radioresistant but they are the m m t heat temperature, although little q
sensitive cells. While low (acid) pH has little effect on r a d i e is available. While blood flow in small animal tumors
sensitivity, acidity leads t o potent enhancement o f heat-induced extensively studied [ I S ] , similar data for human tu
cell killing. When hyperthermia is delivered in association with still sparse. It is known, however, that the blood p
radiation. potentiated cell kill is demonstrated in exceSS of rate in t u n O l S is nonhomogeneous. As a result, if
The CC
power density (W/kg) deposited from an external
what would be expected by simple additive effects of either
IICt thit.
uniform
throughout
the
tumor
volume,
the
result
modality acting independently, d.c., the two
an
tint the
synergistic. This effect may he a result of inhibition of the tUre distribution is rarely uniform. Thereforqsystems
miuw
for
hyperthermia
should
be
expected
t
o
have
appropri
repair of radiation damage in cells b y heat during the postimasubstinti
diation period. These cell studies have been continued in mice control Of Power deposition which can be altered du
, cxtremit
treatment.
and rats where the temDerature rise was induced b v water
- - - ~baths
vumed
R F currents, microwaves, and ultrasound. Recent results o f
1ppiiuti
similar studies in pet animals have shown that the minimum
Iv. WHOLE BODY HYPEHTHERMIA
napme
temperature attained in the tumor was an important correlate
in determining the ultimate success o f the hyperthermia treatI f it is accepted that hyperthermia may be a useful t h n a
ment [ 141. Although many of these factors are poorly undertic modality for cancer, then there is stili th
stood at this time, future unraveling of what appears t o be a
myriad of environmental effects will influence the constraints
on the engineer and clinician in designing or applying hyperthermia systems. If tumor cells are intrinsically at lower p i i
than normal cells, or if blood flow is lower in tumorscompared
to normal tissues during heat treatments [ I S ] , these biological
facton would suggest a favorable condition for producing ceü
fever t h e r a p i a produced whole body hyperther
kill by hyperthermia and might suggest a favorable therapeutic the biological variation attained, the difficulty in co
gain factor (TGF), i.e., a w a t e r effect in the tumor than in
the final temperature. the limit t o the tempera
any treated normal tissue. Hahn discusses these biological
maintained, and the duration o f the fevcr present real drawquestions in detail in a recent monograph [3 1 and summarizes
backs when using toxins. Therefore. certain investigators h i e
many of the important effects in I 11.
become interested in external means o f producing whole body
F o r engineen working in hyperthermia, perhaps the two
hyperthermia (e.&, see reviews 131. 141. l i 6 l - I l 8 1 ) . AmoO
most important biological phenomena of which they should be
the techniques that have been used a
aware are thermotolerance and blood flow. Thermotolerance
is a phenonmenon somewhat unique t o hyperthermia which
has been observed in cultured cells, as w e l i a s in animal and energy, and enclosing the pitimt in 3 ttwipcraiure
human tumors 131. This effect is defined as the apparent
suit. While interestinc. .nalliaiive rcaultr have. becn
< -L~
~ ~ rrnorted
....
wsca
thermoresistance induced in cells following exposure to an
1191, there have been no long-tern1 surviv~tsrrported with la-,
hican,
earlier dose of heat. In other words, a second dose of heat is
method.
,.
..
~
~
~~
~~~~
since^
~~~~
~
-
~~~
.
78 I
I
b¡i PERTHERMIA
.
I
I
I
: :
I
.
'
:
SY+EMS
umbLr of -ups
)r xoducing rcieon
:io
theniaumuinpo ero-depasite
o t n. kuisrn e al. [291. [ 3 I have c&ulatcd tsq~perrturc
niformly w i t h h ~ t u r n o t d u r n $ dittbu,
for t~o-dimenmo$l modrb of t h e s c i y ~ t c m l a o d
'in temoerature dis
ution h u s k t i renilto W
a c that both daiices w i l l often haqe traible
!L
*.”.).un-
*,an.
Fib 3. A schematk of the annular phased array. (al mis fisure show
the two concentric rings with the total o f 16 apertura. (b) An end
view rhowing ü apertures and the radiating wavefronts. Reprinted by
prmbdon O 1982 IEEE.
calculate the temperature distributions for this model, the
electromagnetic fields for the hyperthermia system of interest
must be found. We use a f i i t e element method ( 3 1 1 which
has the advantage that the problem formulation i n c o r p o r a t e
the nonhomogeneous tissue regions. In Fig. 5 we show t h e is*
SAR contours for both a concentric coil and a n annular phased
array model, where t h e SAR (specific absorption rate) is d a
i i i e d as the absorbed power density (W/kg). The SAR value
is given by
where u = tissue electrical conductivity, p = tissue density, and
electric field. The curves in Fig. 5 are normalized SO
the maximum SAR = 1. Note that the t w o devices give very
different SAR patterns, with t h e concentric coil depositing
little power in the tumor (SAR 0.2). while the annulpr phased
array produces a significant SAR gradient varying from 0.1 to
0.6 in the tumor volume. To calculate the isotherms, the SAR
information is used as input to t h e bioheat transfer equation
1321, 1331, which takes into account heat transfer due t o
thermal conduction and blood perfusion. We also solve this
problem using a finite element technique. In Fig. 6 , t h e i s 0
therms for the two systems are shown for a specific set o f a s
sumptions regarding blood flow. The cross-hatched region
indicates the tumor area where the temperature is considered
to be therapeutic, i.e., temperatures greater than 43OC. Note
that despite the large differences in the SAR patterns for the
two systems, the final temperature distributions are not too
different, e&, the percentage of the tumor region greater than
43’C is about the same in both cases. This is primarily d u e to
the fact that the blood flow in t h e surrounding viscera is high
and hence keeps the boundary at close to 37’C, therefore. the
temperature rise is in the necrotic tumor. Also note t b t for
both devices a reasonable percentage of the tumor is n o t a t
temperatures the clinician considers therapeutic. Since actual
blood perfusion rates in normal tissue and tumor vary consid-
üm
B 1-
Pr
ur,
th
th
Cl‘ sean showing a Lrge tumor in
visible are the spinal column, ribs, kidney. and m
I rg. 4. (a) A
o f the CT s u n showing
regions and Ihe finite elemat grid u& in the c
íb) A digitized model
he
en
he
that in the large majority of situations of interest,
rlot be able to bring 7 5 percent o r more of the tumor
prutic temperatures.
There is a need for further m a r c h .
pional hyperthermia systems with prti
tifying the fundamental limitations of
w
OF
Wi
u11
Ih
ab
bu
in
E = the
th
bc
lh
fe
<
ha
in
#th
dC
o tumor to therapeutic temperatures will still bc very
because radiation therapy or chemotherapy will datroY
rrmainder of the tumor cells. However, as yet the clinkb
,.annot tell us what percentage of the tunlor volume must
(rrnperatures greater than 43O to provide an acceplohle dini*
rrsponse.
It is important to emphasize that when the hyprlr n d o nincludes normal tissue, the combination of hcrt na
bt
i ? normal
~
tissue, the interaction hclwcen thc
vill produce unacceptable daniagc in the norm
Iciit to putting more radiation dose into norm
a w already treated lo their tolerance limit. If
¡in
l m
!
in
in
b<
1;
la
tu
1:.
I’
9
Y1
tb
Ih
of trvedom.
VfI.
,lilt
.I:,;,<
lNTtHSTlTlAT
H~PER
I11LHMI.A
T
SVSTqM5
n
'.
t
1
I
1
Fii 8. A dmgram of the dcaipn
by Ihc Dartmouth hypcrtharr,,h
for an interstitial antenna. The fieurc show the crthetn.
and fiber optic thermometry probc.
IMAAH SYSTEM
.,,%
.,.
..
*'<
.,
Fig. 7. Diagram of a radio frequency needle electrode hyperthermia
B
I
Y
:'
Y
system from Astrahan et aL [43]. Reprinted by permission.
number of groups have been investigating the use of invasive
systems, particularly interstitial ones. An interstitial system is
one where the power is deposited through energy sources that
can be inserted through (or a s part of) hypodermic needles or
catheters. Physicians have developed quite sophisticated techniques for placing catheters in most locations within t h e body,
either during surgery or under ultrasound or radiographic control. Presently, three types of interstitial systems are under
investigation: RF needle electrodes, small linear coaxial microwave antennas, and ferromagnetic seeds. In the first case,
usually two parallel planes o f stainless steel needles are implanted near the tumor boundary [ 4 1 1 - [ 4 4 1 . An RF voltage
(typically 0.5-1 MHz) is applied t o the two planes o f needles
resulting in currents between them. These currents heat the
tissue due to its resistive properties. Temperature may he
monitored in the hollow needles in order to control the power.
Recent developments permit switching the powerbetween pairs
of electrodes in order t o provide better temperature control
1431, and inserting flexible cathetfr electrodes which are less
painful to the patient. F i g 7 is a block diagram of a typical
system as described by Astrahan et ai. [ 4 3 1 . Manning et nl.
[ 4 5 I and Cosset et al. 146 1 have reported some very promising
clinical results with this type of system.
The use of linear coaxial microwave antennas was first
proposed by Taylor (471 and has since been refined b y a
number of groups [481-[521. T h e advantage o f a microwave
antenna compared t o RF electrodes is that a single antenna
will radiate power into the surrounding tissue. However, the
physics of the problem dicates that most of the energy will be
absorbed quite close t o the antenna. Therefore, for tumors of
clinical size, it is necessary to implant a n array of these antennas
[ S I ] , 1521. From an engineering point ofview,theseantennas
are interesting because they are immersed in a conducting
medium, and hence, conventional antenna theory must be
extended for this case [ 5 3 1 . When compared t o interstitial RF
needle electrodes, the microwave antenna arrays have the
advantage of being able to be placed farther apart, and hence,
fewer of them need t o be implanted. However, compared t o
the RF needles, it is more difficult to control the energy deposited along the length of an antenna, which has a natural
resonance length. At our institution, these antennas have been
used t o heat both superficial tumors 1541 and &epseated
ones. The deep-seated tumors have been located in t h e abdomen and the brain.
A diagram of the antenna used at the Dartmouth-Hitchcock
Medical Center is shown in Fig. 8. The catheter is a slight
modification of the one used for interstitial radiation therapy.
This catheter becomes part of the antenna design as described
in King et oL 1531. The length of the tip hA is chosen t o
optimize the radiated power patterns taking into account the
catheter, tissue characteristics, and antenna radius. In order to
provide feedback control, the temperature at the antenna is
monitored by a fiber optic temperature probe that is n o t af-
i
&
I1
I
n
C
V
n
1
Fig. 9. A diagram of the microwave system dcvcluprd
a1 Dumw#
used l o drive an array oCinterstitial microwave rntcnnm
t
1
I
I
I
t
Fig 10. A schematic of a ferromaenetic implant system for heath
deep-seated tumors.
fected by electromagnetic fields [ S S ] , [%l.
In Fig. 9 a bloc
diagram of the system is shown. Its major feature is the usem
p i - n diode switches t o control the average power to each 11
tenna using pulsewidth modulation. The power to each ai
tenna is controlled by a feedhack algorithm using the tcmpen
ture information from the thermometry probeshown in F i g 8
Stauffer et aL [ 57 I , I58 I have proposed the use o f fern
magnetic seeds as an interstitial modality. In this concep
illustrated in Fig. IO, the ferromagnetic seeds are deposited i
the tumor volume during surgery. The patient is then pl8m
in a large concentriccoil, e.g.,as in the Magnetrode 1221, 123
I f the frequency is low enough (<2 MHz). then it can be show
that more energy is deposited within the tunior volume thi
in the surrounding nornisl tissue. There is no major advantal
of this system compared to other interstitial systcmg i f t e m p
ature must be measured invasively. However. several resear(
groups are trying t o design seeds whose magnetic propcrtk
change such that at higher tcniperaturcs thc magnetic perme
bility sharply decreases. snd hcnce. the seeds arc self-regulatif
in temperature [ S S ] , 1591. While this systciii has yet 10 I
tested in thc clinic. if is bring tested in sninials snd appean 1
have excellent potential. Its advintage o w r the R F and mitt,
wave interstitial systems is that after the srrds arc implant:
skin incisions can be closed. and hcnce. the implants u n I
left in for extended periods with less risk of infection.
I
i . , : , , r
.
.,
I :
''
I
3.
:IS,
:
1r.11
Iri ' '
.
"'
'
I:
Recently, we set
uce iwrmai tisue tempera
I i-e urixceptible niorbidity
''I
:
-ti
,
t~iii
m e t f r ; at limits that
I ) 11 unicceptable rkk.
'
i
'
i ,t: tiam: not commented on t
i II
'
asan
,
,
[ 13) \\
c , l>ruc?.L
“<rllul*,
I 1 I “ p ” o d . s :\ S>l...i<’l<>.
>r#,l I..
I (;i~Tu<,cL.
r,’\piin\c. t o ‘i>,iitii”rti<<“r \>I Ii>pc.tI>i.ril>i:,2 n d ,adi:,-
t!on.”Rodiolra>.. vol. 123. pi>.463-474.
IP77.
1141 M . W.I>cu.hint.D. A.Sim. S. Sip.iri.10. and W. G. ( onnor. “Thc
importance of minimum tumor icniprraiure in drtrrniininp carly
and long term responres 01 rpontanrour cminc a n d felinr tumors
to heal and radiation.’’ Conccr RES., WI.4 4 , pp. 43-50. 1984.
1151 C. W. Sonp. A. Lokrliina. J. Rlicc. M. Pallen. and S. H. Lcvitt.
“implication of blood flow in hyperthcrmic treatment ufrumors.”
IEEE Tmns Biomed. Eng.. vol. BME-31. pp. 9-16. Jan. 1984.
(161 P. M. Corry. O. H. Frazicr. J. M. Bull, and B. Barlope. “Methods
for induction oí Systemic hyperthermia,” in Physicnl A~ppcetsof
Hypenhrnnin, G . H. Nussbaum. Ed. New York: Amcr. Inst.
Physics, 1982, pp. 587-599.
(17) J. M. Bull. ”Systemic hypcrthcrmia: Background and yrinciplcr.”
’ in Hypenhennw in Concer Therapy, F. K. Storm, Ed. Boston,
MA.: Hall Medical Publishing, 1983. pp. 401-406.
[ I S ] L. C. Parks and G . V. Smith, “Systemic hyperthermia by extracorporeal induction: Techniques and results,” in Hypnlhermio in
COnCCr niempy. F. K. Storm, Ed. Boston, MA: Hall Medical
Publishing. 1983. pp. 407-446.
1191 R. T. Pettigrew. I. M. Gall, C. M. Ludgate, D. B. Hom, and A. N.
Smith, “Circulatory and biochemical eifectr ofwhole body hyperthermia.”Br. J. Sur~.,voi. 61,pp. 727-730,1974,
(201 R. Cavaliue, G . Moricca, F. DiFilippo, L. Alae, C. Monticelli,
and F. S. Ssrtori. “Hyperihennic perfusion 16 years after its first
clinical applications,” Henry Ford Hosp. Med. 1. vol. 29. no. 1,
pp. 32-36.1981,
121 1 J. S. Stehlin, Ir., B. C. Giovanclla, A.E. Gutierrcz,P. D. de Ipolyi,
and P. J. Greeff. “15 Years exverience with hvnerthcrmic oerfusion for treatment oí soft ti&
sarcoma and malignant melaenoma
of the extremities,” From Rodúrl. Ther. Oncol.. vol. 18. J. M.
Vaeth. Ed., pp. 177-182, 1984.
1221 F. K. Storm, W. H. Harrison. R. S. EUiott, A. W . Silberman, and
D. L. Morton, “Thermal distribution of magnetic-loop induction
hyperthermia in phantoms and animals: Effect of the living statc
and velocity o i heating,” hf.I. Rod OnroL BioL m y s , vol. 8,
pp. 865-871,1982.
1231 F. K. Storm, W. H. Harrison, R. S. Elliott, and D. L. Morton,
“Physical aspects of localized heating by magrietic-loop induction,” in Hyperthermia in Cancer Theropy, F. K. Storm, Ed.
Boston, MA : Hall Medical Publishing, 1983, pp. 305-314.
(241 P. F. Turner, “Regional hyperthermia with an annular phased
array,’. IEEE Tmns Biomed Eng., vol. BME-31, pp. 106-114,
Ian. 1984.
1251 F. A. Gibbo, M. D. Sspozink, K. S. G a t s , and J. R. Stwart,
“Regional hyperthermia with an annular phased array in cxprimental treatment of cancer: Report of work in progress with P
technical emphasir,”IEEE Tmm Biomed. Eng..vol. BME-31, pp.
115-119, Jan. 1984.
I261 I. R. Oleson, “Hyperthcmia by magnetic induction: I. Physical
characteristics of the teshnique,” Inf. 1. Rod. Onml. Biol. Ayr.,
vol. 8,pp. 1747-1756.1982.
I271 J. R. Oleson, R. S. Heusinkveld, and M. R. Manning,“Hypcrthermia by magnetic induction: 11.Clinical experience withconcentric
electrodes,” Inl. J. R o d Onml. BioL P h y s , vol. 9 , pp. 549-556,
1983.
(281 M. F. Iskandcr, P. F. Turner, J. E. DcBoiv, and J. Kao, ”Twe
dimensional technique to calculate the WI power deposition
pattern in the human body.” J. Microwave Power, vol. 17, pp.
175-185,1982.
129) K. D. Pauhcn, I. W. Strohbehn, S. C. Hill, D. R. Lynch, and F. E.
Kennedy. “Theoretical temperature profiles for concentric coil
induction heating devices in a two-dimensional. mi-asymmetric,
.
Phys.,
inhomogeneous patient model,” Inf. J. R a d O n ~ lBiol.
vol. 10, PP. 1095-1107, 1984.
130) K. D. Pausen, J. W. Strohbehn, and D. R. Lynch, “Theoretical
thermal dosimetry produced by an annular phaed array type
system in CT-bared patient models.” Rod&. Res., vol. 100, 1984.
1311 D. R. Lynch, K. D.Paulsm, and J.W. Strohbehn, “Finite element
solution of Maxwell’s equstions for hyperthemil treatment
planning,” J. CompufationolPhyr, accepted for publication
(32) M. M. Chen and K. R. Holmes. .“MierovasculPr contributions in
tissue heat transfer,” in Therm01 Charocrerisfics of Tumors:
Applications in Defection md Trearmenl, R. K. lain and P. M.
Gullino. Edr. New Yoik: NYAS; vol. 335, pp. 137-150, 1980.
(331 R. K. J a b , “Bioheai transrer: Mathematical models of thermal
Systems,” in Hyperrhermio in Cancer Therapy, F . K. Storm, Ed.
Boston, MA.: Hall Medical Publishers. 1983. pp. 9-46.
_ 1
in tissue: An adjunct to tumor therapy.“ hled. lnsrmm,,y~if4j;
,,.
pp. 16-21.1976.
..,.<(
.=,
1421 E. W. Gcrncr. W.G . Connor. M. L. M. Boanc. J . D. Da. P
Mayx. and R. C. Miller. “Thc patcntial ufloc~irtd
adjunct to radiation thcrapy,”Rodidoby. val. 116.
1975.
1431 M. A. Astrahan and A.Norman, “A localized currcn
thcrmia System for u x with I9biridium intentiti
Med P h y s , vol. 9 , no. 3, pp. 419-424,1982.
1441 1. W. Strohkhn. “Temperature distributions
electrode hypcrthcmu systems: Thcoretio
J. Radiar. OnmL BioL F i ~ y rvol.
, 9 , pp. 1655
(451 M. R. Mannin8, T. C. Celar. R. C. MiUer. J
Connor, and E. W. Cerner, “Clinical hypcnh
phase I trial employing hypcrthcrmia alone
with external beani or intersti1i;il radioihcnp
pp. 205-216, 1982.
(461 I. M. Cosset, J. Dutrek, I. Dufaur. P. Jsnoray. E
and D. Clarke. “Combined interstitial hyperthc
therapy: lnstitute Gustave Rouuy technique
results,” Inr. 1. Rod& OneoL Biol Phyr, vol.
1984.
(471 L. S. Taylor, “Electrumagneiic ryrinpc,” IEEE 7hm.
Eng..vol. BME-25, pp. 303-304, Mu. 1978.
1481 L. S. Taylor. “Implantable radiaton fur cancer thcnpy
wave hyperthermia,” Roc IEEE. vol. 68, no. I. pp,
1980.
(491 G. M. Samaras, “Intracranial microwave hyperthermia
duction and temperature control,” IEEE Tmm. Biom
vol. BME-31, pp. 63-69, Jan. 1984.
1501 D. C. dc Sicyes, E. B. Douple. J . W.Strohbehn
“Some aspects of optimization oran invasive
for local hypcrthcrmia treatmcnt of cancer?
PP. 179-183.1981.
1511 jl W. Strohbchn, B. S.Trcmbly. and E. B. Douple. “Blood 6:
’.:
effects on the lemperaturc distributions from an invasive m-:
~:
wave antenna array uscd in cancer tlierap)..”IEEE zíons Bo*.8,,;::.
,&U
Eng.,voi. BME-29, pp. 649-661, 1982.
(521 B. S. Trembly, J. W. Strohbchn. D. C. de Sicycs, and E.
Douple, “Hyperthermia induced by an array of invasive m i a P
wave antennas,’* J. Nnf. Concer Insr. mono^.. rol. 61. pp. 4Vl499.1982.
i in’
I531
W.P. Kim. B. S. Tremblu.
”Thr
- ... ...~~.
. c*c
. . R.
.. and 1.- W.Strolihchn.
tromnpnetic field of an inrulatcd m t c n m in a conducting o<
PI
diekctric medium,” IEEE Tianí hlicmwir nmry Te&.,
he
an
MTT-31, pp. 574-583. 1983.
154) C. T. Coughlin, E. B. Douplc. J. W.Strohbchn. H’. L. ~:atonJ:-::
B. S. Trembly, and T. 2. Wong. “Interstitial hyprrthcmi
’ :.
combination uith brachythrrapy,” Rodidom. vol. 148. R ”: 1
*%’!
&,
~~~~~
_”_.
?QL?QQ
l.,I_.
OP2
-1-
~
~
155 J D. A. Christensen. “Anew non-prrlurhinF tcnqvr~lurcPI&
using semiconductor hand edgc shift,” 1. Bior>v.. vol. 1.
543-545,1977.
SiJr~iicaIEle trot ect nology: Quo Vadis?
rtm.r.-nir dnielopmenl of the moderii el<.cl
Its tecwsurhr Is ouniiied. The UP o f the tie<
mnipiinil to ,>IhnIkmil knkor: (he pl:iwna rc
Ihi w&i<rim c f
the
(he&.:docbpde is humr:~
porrlians i
si:nd<Wtic de:uorqety arid the
.,n
iiimmd, ilono wlUi a unimiry df wmc curre,
&eclion m d wavefonri &encra<ing technique in
~!ttnontntn
of e l ~ t i o s u r g bgnmtow.
l
1
INTRODUCTION
HILE the u x o f ,electricity in tlicrag o t
ssrvati\t,Iy dates back to the 161ti cm
ilation f o r the application oEelectricai i
:tiiii+s wiis hid hy d'/monval 3 c e i i t u i
reIiorti:d his expeiinien tal observaiiiin rn:
: 1 aliovc 113 kHz coiild be passed 1lirou:h
h u t i:vMence o f pain or nsuroniu+wl;i
W h therinal i:ffcsts were noted [ Z ] . I i
wwtniteil an alcc:tricai appwtus that , I r
I m
t niodernti: voltages: he camductad r
':til oxpenrnentr with ar imalr and is,olatId
~urat:iona131. Siimiiltanwudy, Teda a:;<
Wion coil systcnis w h r h produced m1.c
11: N.ii(ebchmidt. ir 11191, dsmonrtrs':%
:in8 t:l'l'wti of h$i-lrequency currcnts t ',I
':lculat<iiy diseaires a i d waa amoris : h(
<$
medicine ccmy[II.thercal
cnts in surgical
ater. In 1891,
ilternating cur.
ir human body
. t h u l d i o n , al.
9 3 , ü.4rsonval
uccd large curiher of phyaiowe and muscle
idin developed
iigher voltages,
he efficacy of
eating articular
irst to use the
iliucript icceived July 30 l984:1cvired Ssp I:/ :r11.1984.
1,: author i.1 wilh lhe Ik{imment of 171,:cir ..I i d Compuisr
113.524.
O0
i
E"
r
.
..
Technicalnote
n
i
+)
Digital temperature controller for
low-temperature light microscopy
i
M. R o s e n t h a i
Division of BioEnginesnng. MRC Clinical Research Centre. Harrow. London HA1 3UJ. England
W. F. Rail’
ARC lnslifule of Animal Physiology. Animal Rtaaarch Station, 307 Huntingdon Rosd. Cambridge Cü3 Wü.
England
KeywordkCircuiC Control system, Cryomicroscopy, Tempersture
Med. & 8iol. Eng. & Comput. 1984. 22.471 -474 )5
over the range 0.25 to 4 250’Cmin-’ and allows the
specimen temperature to be held at any desired temperature
between =: -150 and +40cC.
PERATURE light
microscopy or cryomicroscopy is a
tool for examining the deleterious erects of freezing
awing on biological milterials (LUYETand PRIBOR,
LER et al.,1976 MCGRATH
rr al.. 1975; RALLet al., 2 M e c h a n i c a l heater s t a g e
need exists for a simple. reliable cryomicroscope
REID(1978) described the construction of tiie mechanical
hich permits a high degree of flexibility. Cryoheater stage. Briefly. the stage consists of a machined brass
design can be separated into two parts:
block through which cold gaseous and/or liquid nitrogen
circulates (Fig. I). The brass block is attached to the “y
mechanical stage which is mounted on a light microsubstage of a light microscope. Heat conduction between the
scope and couples the heater to the specimen
block and the substage is minimised by a thin piece of
an electronic servocontrol system which allows the
Styrofoam
and the use of nylon screws to attach the block to
specimen temperature to track a programmed temperathe
substage.
A slide-heater assembly (Fig. 2) is placed on top
ture against time profile.
of the block. Electrical insulation is provided by a piece of
(1978) decribed a cryomicroscope which incorporated
clingfilm (or household plastic wrap).
ust mechanical stage and a motor-driven potentiometer
The beater slide is constructed as follows. First, a thin film
ce temperature ramp. We now report a
of chromium metal is vapour-deposited onto one side of a
ign which couples Reid‘s mechanical
glass microscope slide (75 x 25 x 1mm). Then a l2mm wide
gitally generated reference temperature.
section in the middle of the slide is masked and a thick layer
gn permits programmed cooling and warming rates
of copper is vapour-deposited on the chromium. The
resistance across the chromium section of the heater slide
should ideally be within the range 150-25OQ. A foil
copper/constantan thermocouple (No. 20108-1. Rdf Corp..
Hudson, New Hampshire, USA) is placed on the uncoated
side of the slide and sealed under a 22 x 26mm coverslip
using a clear histological mounting medium (e.g. DPX).
Electrical contact between the slide heater and controller is
made by attaching a thin sheet of copper foil to the edge of
thermocouple
\-
coverglass
1address Amerrcan Red CJOSS
Blood Research Labomtorrss,
,”*‘ecelved 13rh Sepremner and in lrnnl form 7th November 19H.3
l%IE
%al
1%
a Biological Engineering
Computing
September 1%
471
‘.,
f i g :. \ t ! t , w \
l ~ h e\olt:,gc
I uliciii.i:iL. u:.igr;im
h c t w c i . i i i t i c Iir.:it<r-\liJc
(u) to produce an accurate amplified version of the iher-
mocouple voltage
( h ) to produce a reference voltage in the form of a linear
ramp with a programmable rate of rise and pdii and the
íacility to hold the ramp voltage at any preset level
(c) to compare the amplified thermocouple voltage with the
reference voltage in a servocontrol loop and provide
sufficient power to the stage heater to minimise the
diíTerence between these voltages.
bier slkie
ct7mple1e sysl
jiiiiction ihcld in liquid n i t r i w n at
196 )is
ampliíicd h! A l w i h J t a slide tempcr.iiurc or +JO
I V output. Thc amplifier cmplo!cd fin this task is
Inicrsil lCL7M)I. Hhich is a monolithic chopper am
with a stable offset koltapc ttempcraturc cw
< O-I/iV c - f ) .
The programmed ramp voltage is derived írom a 34
upidown counter clocked by a variable rate astable
3-digit BCD digital-to-analoguc convertor. The cl
can be any of 10 preset values to yield the desir
of coolinglwarming.
The user can sei the upper and lower l
i
cool/warm cycle by using two sets of BCD
switches. The siage temperature can be held i
either of these limits. A temperature ‘hold’ posit
obtained in the following manner. I f the cool/warm
(upidown) is in the warm position, one input of gate A
high. When the output of the BCD counter is equal
setting oí the upper limit switch, the output of magnit
3‘
ani
10‘
gal
eqL
ma
hiF
3.2
A
ami
volt
slid1
refo
to II
In
was
the
Iran:
heat,
ad@
over:
lider
temp
I
I
coi
.
-
relircncc
3 Electronic circuitry
3. 1 G m , r u l schiwi.
The design objectives for the heater control circuit are as
roiiows:
!!IC
ihcimi~c(>uple
andem.
must
Th
heate
lLl2
Whei
ihan
SWitCI
the to
&
lyi
l
prod i
perioc
hold
geld
iempe
gain c
4 op4
4.1
Fig.
3 Schemafic diagram of
rlie hearer controlcircuit
;
1;
o
Fig. 4
Circuit
diqrants oii*oseri-oconrrolloops rlioi supplJponer I O the slide hraier
b
’
P,
We
durin@
@!Ter 11
We
amhient
!e\;!
\vhi!e t i e su5stay is coo!ed and final preparations made before controlled cooling and wmni::~
4lternati\el>. specimens can be sealed between two covzrglasses
and cooled Ie.g. quench frozen) belore transfer onto a
precooled heater slide and then examined duriii- warming.
red ra:C
I.
to, I:?
nbulki
nite!). 31
,¡tic i)
2
s$...ch
4 is held
II te.'hc
ign: d e
.\ servocontrol loop uiis achieved by comparing the
lmpliíied tlicrniocouple voltiige with the programmedramp
idtape in ;iniplitier A 3 :ind supplyingsufficient power to the
\lids heatcr to eniiblc thc stase temperature to track the
:eference \olt:ige. Two methods were used to supply power
:o the heater in response to the output of A3 (see Fig. 4).
in the initi:iI system (Fig. 4dI.a DC supply for the heater
ras used. Thc operator sclects the total voltage available to
:he heater uith an extcrniil potentiometer. A buflered
:nnsistor driver then controls the Dower dissioated in the
beater. To achieve proportional control, the gain of A3 is
idjusted such that at 'hold' temperatures there is minimum
uvershoot. The resultant pseudoproportional control provides good temperature control at a particular brass stage
temperature. but the gain of A3 and/or the heater voltage
must be readjusted ifthis is changed.
The Iatest circuit (Fig. 4h) couples a 50V AC supply to the
hater. Control is achieved using a zero-voltage switch
ich triggers a triac ina proportional-controlmode.
he voltage at point 0 of Fig. 46 is at a lower voltage
e bottom of the internal ramp of the zero voltage
the heater is on. and when the voltage is higher than
of the internal ramp the heater is ON.Voltages at point
between the bottom and top of the internal ramp
bursts of power to the heater. The internal ramp
adjusted to give optimum stability of the stage at a
temperature. This circuit arrangement was found to
better stability over the whole range of brass stage
atures without the need for further adjustment of the
f A3 or thc supply voltage.
4.2 C~litir~irioii
re.m
REID (1978) has described the use of aqueous salt and
sugar solutions with knoun melting and eutectic temperatures to examine the capabilities of particular heater assemblies. Such calibration tests permit measurement of the
difference between tlie temperature of the specimen and the
temperature of the stage thermocouple. temperature
gradients in the horizontal (across the field of view) and
vertical directions, and the rates of cooling and warming
under various conditions.
Operation of the cryomicroscope
ucticd ciiiisiderurii>iis
9r
I
W
have examined a wide variety of biological material
Cering and thawing over the past five years and can
following practical advice.
ve mounted our cryomicroscope stage on a Wild
roscope equipped with phase-contrast optics. The
kness of our machined brass block assemblies (9 or
1 requires the use of a long working distance conThe voltage of the thermocouple in the slide-heater
ly is continuously measured with a potentiometric
er. Recorders capable of steps of 100 per cent zero
event markins are particularly useful. Records oí
rance o í a variety of specimens during cooling and
h3\e k e n m:ide on time-lapse videotape. 16mni
m and or ZSmm photographs.
buildup oí írost on the brassstage and spewimen slide
'n interfere with observations. especially when low
xioling :ind warming or entended holding periods
.red. O n e wlutiiin is to cnclnse the brass stage land
the niicroicopc ifnccesaryl in a plastic hag and
h.y urth <Ir> .¡ir <iri i i i r o p ~
Entry port>in the ha)!
.W tilc iiiCid~~ip_
o
h:llllpie~.
i
adling .ind cirientaiiiin <,í\ample>on ihc rlidc ib hesi
ishcd uheii iiic bra>, ?iage I I J t amhient tempera~ c i m t r ~ ~i .Itkn rni.tint.1111the ,.implc temperature ai
I6 Biological Engineering 6 Computing
Oneexample oíacalibration test isshown in Fig. 5. F'irsta
small drop of a I 5 per cent weight NaCl solution was placed
directly on the centre o l the heater slide assembly and a
coverolass placed on top. The controller was adjusted to
maintain the temperature of the sample at
?O C and
sufficient cold giaxous N, was then passedthrough the hrass
tag^ to cool and maintain the substage at -60 C . Thc
controller was then adjusted to cool the specimen at
I C min and a series of photographswere taken us ice and
eutectic salt cr)stals grew into a field of view approximatel)
400Iim from the thermcuiuple junction. Ice cr\it.ih appeared uhcn tlic i
d thermocouple indicated .I tcmpcr:i[urc
<\¡ - 9 5 í. 1 1 . i ~ i d i Thc pubihhed freeiing p<i;nio1 tk,i,
September 1984
-
~
'
473
wiiition
I*
-
ii (
iHt~i,
<I
<I:.. i L h ? i . u I , i L b
nJir.i::.
.i
timpcrature dilTcr<:ncc< i f 1 5 (' hcturcn ihc t h c i n i < u ' i i p ! r .
and the ohscr\ed lield oí l i e u . O n continued coding !he
quantii! oficc gradual¡) increases 1Figs. Sh and, I. and upim
reaching a thermocouple temprature oi -23 5 C- small
dark crystals of eutectic salt INaCI~?H,O)and ice formed
between thc large ice crystals IFig. Sdi. A puhlished eutectic
temperature of - 2 C I D A M rt u/.. 1962) indicates that a
constant temperature dillerence of 1.5 C was maintained
between the thermocouple and sample during cooling. The
controller was then adjusted to harm the sample ai
1 Cmin- and the crystalline materials melted at the same
temperature ai which they formed. The constant temperature difíerence (1.5 C) therefore permits the accurate determination oí the temperature oí this sample horn the
measured thermocouple temperature during controlled
cooling and warming.
'
Acknodedymrnts-We thank Professor Heinz WolR lor providing
research facilities and J. Baker for consultations on the circuit
.
IiEI. rR4NZhCTlCNS ON tllOMEOICAL ENGIKEERING. VOL. RME.34. NO. 5. MAY 1987
c9
375
A Whole Body Thermal Model of Man During
Hyperthermia
hyperthermia procedures complained of pain at particular
areas of the body outside o f that being treated by the regional applicator. Significant increases in cardiac output
during regional hyperthermia have also been described
[3], [4]. These clinical findings illustrate the need for a
whole body thermal model o f map, adapted for hyperthermic conditions, which can aid in predicting the hot
spot locations and @e extent of cardiac stress.
Several mathematical models have been formulated to
describe whole body heat transfer in man [5], [61, [7].
One o f these models has been applied to hyperthermia [8],
[9], [IO] but the simulations did not include surface cooling with sprayed water and a circulating water bolus which
may be used by the clinician to decrease patient discomfort during a treatment. Also, the effects o f nonlocal, or
“aberrant,” energy deposition were not considered.
INTRODUCTION
Aberrant heating is especially significant when frequenHE use o f hyperthermia as an adjuvant cancer therapy cies below 1 GHz are used to treat deep-seated tumors.
has been documented by many research ‘groups [ 11. Results from a three-dimensional block model o f man [ 1 1 1
Recent studies have shown that hyperthermia treatments’ are used in the present study to determine theoretically the
administered in conjunction with radiation therdpy and magnitude of nonlocal heating during regional hyperchemotherapy can be effective in reducing tumor size and thermia.
ultimately eliminating the tumor. This laboratory is curThe objective of this investigation is to quantify the
rently developing a system which utilizes electromagnetic systemic physiological response to regional heating using
energy in the radiofrequency (RF) range to induce hyper- a whole body thermal model of man. Theoretical calcuthermia in humans. The applicators being considered for lations of R F energy deposition throughout the body, acimplementation of the hyperthermia treatments are the counting for aberrant energy, are input into the model so
miniannular phased a m y (MAPA) and the annular phased that the effect o f this phenomenon can be observed. The
a m y (APA), which are manufactured by the BSD Medi- various cooling methods needed to maximize patient comcal Corporation.
fort and minimize increases in cardiac output, thus inThe development of a safe clinical hyperthemiia pro- creasing patient tolerance for torso heating, can then be
tocol requires a priori knowledge o f the effects o f R F evaluated via this model.
energy deposition and surface cooling conditions on regional temperatures, blood flows, and evaporation rates.
I. OVERALLHEAT BALANCE
EQUATIONS
It has been reported [2)that patients undergoing clinical
In this model, man is subdivided into 16 body segments:
head, neck, two upper arms, two lower arms, two
Manurcnpt rcccivrd September 10. 1986; revised December 1. 1986.
This work was pcrfomed hy the authors as pan of their employment by
hands. thorax, abdomen, two thighs, two lower legs. and
lhc US üovcrnment and as such h i s piper ir not subject to US copyrighi two feet. All o f the body segments are considered cylinPmtecti<in.The opinions in this paper am solely those of the authors and
do no1 n e i c i ~ n l yrrlieci official HHS opinion. Mention of trade names of drical in shape, except the head which is assumed to be
c o m m c ~ c ~ npnrlucir
I
d r r i nul constitute cndorrcment or mcominendstion
spherical. in addition, there is one central blood comfor “IC by HHS
partment. Each body segment is further subdivided into
C , K . Cham) rod R . L. k v i n afe with Biomedical Engineering and
InrtNrncnidi!<inBranch. üiuiriim of Research Services. NiH. Bcthesdn. four concentric layers; namely, core, muscle. fat. and
hlD 208’4: rnd the Vcprninent in¡ Biomedical Engineering The lohnr Hopskin. Thus, there are a total of 64 body elements plus one
kin5 Unirrrwiy Schrwl <>¡ CIcd~cinc.Biliim~rc.
M D 21205
central blood reservoir. Each body element “ i ” ( I 5 i
M. I. Hdyminn 13 with Dcpnnrnent of Elecincil Engmcenng. Florida
5 64) is characterized by a temperature ifi 1, volume
Iniematwnr~~ k v r r w ~ .
FL u t 9 9
V(i),s u r f a c r a r e a S ( i ) , d e n s i t y p ( i ), specilk h e a t c ( i ) ,
IEEE L o p ‘iiiinhcr $ b ~ l ; ! : d
Ah:ifnwf-A whole body thermal model or man hrs been developed
the changes in re;ionil t e m p n t u m and blood llowr during
hyperthermia treutments with the minhnnular phased array (MAPA)
and :,nnular phased army (APA) applkatoorr. A model al the thermoregiilstory response lo r q i o n i l heating based w the experimental and
ounierical studies ot others b u bmi lncorpontcd into thls study. Experimcnidly oblained energy de*position pittrrna aitUn a human leg
erpwed la lhe MAPA were in@ into the model and the mulla were
compured to those based upon a thmretical depoaltion pattern. Exposure o í the abdomen to the APA WM modeled with and without the
oberrnnt energy depositlon that k M been described previously. Results
or the model reveal that therapeutic heating ( 742°C) orextremity roil
tisuc sarcomas is possible without signiíkant systemic heating. Very
high bone tempcrutureo ( > S O T ) were ohtiined when the erperimenbI uhuirplion pattern was u d . Ciiculiiions show that rystemk heating due IO APA exposure is reduced via evaporative spray cooling techniques coupled with higb-velocity amhicut air Bow.
10predict
T
r
.
-.
1.30
4 42
0.01 16
0.060
I .m
1.01
1046
6.97
0.0016
0.050
1.w
10.46
0.001I
0.400
1.36
6.81
0.0013
o 1w
7.52
om28
o 800
1.10
9.11
0.w11
0.100
11.41
3.21
I
.w
10.46
...
...
...
...
thermal conductivity k ( i ), electrical conductivity u( i ),
basal metabolic rate Qb(i ), basal evaporation rate Eb(i ),
and basal blood perfusion per unit mass o f tissue wb(i ).
The blood compartment is characterized by a single temperanire Tb, volume
density pb.and specific heat cb.
Values of these physical propenies were obtained from
the literature [7],[i2] (see Table I).
The energy balance equations for the body segment “j”
( 1 c j c I6)are
I) core:
v,,
- 3)
aT(4j
- 3)
at
= Q d 4 j - 3) - Q m d 4 j - 3) +
+ Q,(4j
- 3)
- E(4j - 3)
+ Q d 4 j - 3) + Q,I
2) muscle:
C(4j
- 2)
aT(4j
- 2)
at
3)far:
C(4j
-
i)
W(4j
at
-
1)
0.0
0.61
0.81
O 79
C(4j
.
0.0 0.39
0.0012
-1.
4)
1.86
o01
4.27
0.0
. 10.55
1.0
14.22
0.81
.
5.19
c.0
0.11
skin:
+ Qmet(4j) - E,pny(4j)+
+ Qd4j) - E(4j)
- Q,,
where C ( i )= V ( i )* p ( i ) * c ( i )and Qconv
is the heat
transferred to the tissue by convection with the perfused
blood (see Section 11). Qcodis the heat transferred between tissue layers by conduction (see Section 111).Q,
is the rate o f metabolic heating (see Section Vil).
is
heating by muscular work (see Section VI-B), Qñ is the
rate of electromagnetic energy deposition (see Section V),
E is the evaporative heat loss from the element (see Section VIII), Qpnl is the heat exchange between the lungs
and the blood in the pulmonary system (see Section X),
Qcnv is the heat loss from the skin layer to the environment
via convective heat exchange (see Section IV), and ESP”>,
is the heat loss from the skin layer to the ambient air via
externally applied water on the skin (see Section IX).
Each body element is also characterized by a “setpoint’’ temperature. The set-point temperatures are determined by the method described by Stolwijk [SI. Under
steady-state conditions, with thermoregulation turned off,
zero RF-energy deposition, and basal metabolic and evaporation rates, the 65 energy balance equations (see (I)(4), (9)) are solved simultaneously under a set of thermally neutral ambient air conditions (29°C. 20 percent
relative humidity, O. 1 m / s ) . The resulting set of 65 temperatures are the set-point temperatures.
11. CONVECTIVE
(VIA PERFUSION)
HEATTRANSFER
TERM
Convective heat transfer occurs between the tissue element “i” and the blood which perfuses this tissue according to the equation
Qcon,(i) = p ( i ) *
v ( i )*
* (Thgn(;)
-
(ph
* 4;)* c h )
Th.nil(i))
(5)
I \RN\’
rt Lil’ rllERM.AL MOIIEL OF MAN DURING HYPERTHERMLA
’>. here
h e sul>~cripts“in” and “out” represent the prop-
cilies iolthe Iilood entering and leaving the body element,
r:,\peciively Assuming complete thermal equilibration
kctween the iissue element and the blood leaving the eleI,.
cnt:
Tb.o.(i)
T(i).
(6)
11is also assumed that blood enters each tissue element at
~;t,csame teiiiperriture (¡.e., there is no preartenole heat
i:r;insfer with the arterial blood) so that
=
Tb.in(i)
(7)
Tb.
311
L ( i )is the length of element “i,” and rl and r2 are the
radii at the midvolume and boundary of element “i,” respectively.
WITH THE ENVIRONMENT
IV. HEAT TRANSFER
The ambient air conditions (temperature, velocity, and
relative humidity) are inputs to this model, as are the conditions for heat exchange with a constant temperature
water bolus which surrounds the area treated by the applicator:
Q...(j>= W j )
‘I’liUS,
Q d i )=
d i ) * v(i)* ( P b * 4 i ) * c b )
* (Tb - T(i)).
* (T(4j) - T,) + H d j ) *So‘)
* (T(4j) - &)l.
(8)
‘The temperature of the central blood compartment is calciilated by assuming that there is no postcapillary heat
tfitnsfer with the venous blood and that the venous blood
i i well mixed in the central blood compartment. The heat
belance equation for the blood may then be written as
(14)
H i s the heat transfer coefficient between the skin element
and ambient, while i f b is the heat transfer coefficient between the skin element and the water bolus.
H( j ) is determined via the following expression [51.
H ( j ) =(H,(j)+ H c ( j ) * 3 . 1 6 * v o 5 ) * S ( j )
(15)
where H, is the radiative heat transfer coefficient in W / m 2
. “C between the skin and the surrounding surfaces, i f ,
is the convective heat transfer coefficient in W / m Z “C
between the skin and the air, v is the air velocity in m/s,
and S is the surface area of the body segment. The water
bolus heat transfer coefficients are estimated as
.
* ( T ( i )- T b )
-
QWl.
(9)
’rile value of u( i ), a function of local and body skin tempcratures, is determined by the thermoregulatory model
ilcscribed in Section VI.
111. HEAT TRANSFER
BY CONDUCTION
Heat is assumed to be transferred by conduction within
a body segment in the radial direction only. Axial coniliiction between adjacent body segments (e.g., between
the hand and lower arm. head and neck, etc.) is neglected,
and azimuthal symmetry is assumed within each element.
The heat conduction between two radially concentric body
r:lements is modeled by the equation
(10)
= G d i ) * ( T ( i )- T(i + 1))
where Gem(
i ) is the effective heat conductance between
(issue elements “ i ” and “ i
1.” The effective conductance between two adjacent tissue elements is a funclion of their geometries and thermal conductivities and
can be determined by the series addition of the individual
conductances of each tissue element based upon the dislance between the tibsue boundary and the midvolume radius of the element. Consequently,
&(j) =
iO*Hc(j).
(16)
Values of H,and H, for the 16 body segments were obtained from the literature [5].
V. ELECTROMAGNETIC
ENERGY
SOURCETERM
The RF energy deposited within a body segment “j,”
Qdep( j ) , is assumed to be subdivided into the four tissue
layers based on a volume-electrical conductivity product
weighted average, i.e.,
Core:
QoId
+
G ( i )=
4ñk(i)
l/rl
-
I/r2
G ( i )= 2 ñ k ( i )L ( i )
In
‘rhere k ( i )
IS
r./rl
for a sphere
(12)
fora cylinder
(13)
ihr themiill c~inductiviiyof element “i.“
(17)
Muscle:
Skin:
where VS( j ) = V ( 4 j - 3 ) * o í 4 j - 3 ) + V í l j
* o ( 4 j - 2 ) + Ví4j - I ) * o í l j - 1)
- 2)
vía¡)*
o ( 4 j ). Experimental values of the subdivision of RF energy within a human lower leg were also used for the case
of MAPA exposure.
.
Vi. MODELOF HUMANTHERMOREGULATION
A. Conrrol of Skin Blood Flow
The expressions used to describe human thermoregulation were obtained from a model developed by Stolwijk
151. Based on this work, the vasodilation and vasoconstriction o f blood vessels in the skin layers depend on an
"integrated" whole body skin temperature signal, the hypothalamic (;.e., head core) temperature, and the local
skin temperature. The skin temperature signal for a body
segment "j," represented by the parameter ERROR(4j).
is calculated for the 16 skin elements as follows:
ERROR(4j) = T(4j)
(211
- Ts,(4j).
All positive values of ERROR ( 4 j ) are summed to form
the parameter WARMS, while all negative values of ERROR(4j) are summed and set equal to the parameter
COLDS. Each ERROR ( 4 j ) term is weighted according
to the factor SKINR ( j ).which is proportional to the density of temperature receptors on the skin o f segment
'>."
WARMS
c ERROR(4j) * SKINR( j )
J-1
COLDS
16
=
- c ERROR(4j) * SKINR( j )
J=I
ERROR(4j)
+ SKINV(j) * DILATI(p(4j) * Y(4j))
1 + SKINC( j )
* STRlC
(27)
where wb is the adjusted basal blood flow (see below) and
SKINV ( j ) and SKINC ( j ) are weighting factors which
are proportional to the density o f vasodilation and vasoconstriction effectors on the skin element "j." respectively.
Based on published reports 161, 171, regional blood flow
depends on the local temperature as well as the central
command described in (27). The relationship used in the
present model is that the basal skin blood flow is doubled
for every 4.5 "C increase in local temperature above the
set point temperature of that element and halved for every
4.5 "C decrease in the local temperature. Therefore,
* 2,0ERRORí4j)/4.5
.
(28)
others [6]. A first-order exponential equation was denved
which predicís the change in skin blood flow as a function
not only of skin and brain temperatures, but also of time.
ERROR(4j) < O. This is the same approach used by Wissler [6] to model
the delay in human cardiovascular response. For the time
(23)
step "n"
* ERROR(I) - 5.0 * (WARMS - COLDS)
(24)
DILAT
SWEAT
+ 29.0 * (WARMS -
- u.,
u,
w,- I
- W",
= exp ( - A t / r )
(29)
where ,
.u is the desired skin blood Bow predicted by the
original thermoregulatory model as a function of skin and
brain tempekture only (which represents the perfusion
after infinite time), A? is the duration of the time step, and
r is a time constant.
B. Control of Muscle Blood Flow
Muscle blood flow can be increased by either a central
shivering command, based on Stolwijk's themoregulatory model, or a local controller, which was not included
in Stolwijk's work. All of the hypenhermia simulations
(25) assume that the patient is at rest, so any muscular work is
due to shivering. It is reasonable to assume that there is
no shivering in the basal case or during a hyperthermia
treatment. Thus, in this model the muscle blood flow depends only on a local control mechanism.
COLDS)
As reported by Sekins et al. [13], the blood flow to
(26) muscle during a hyperthermia treatment depends on the
* ERROR(I) + 7.5 * (WARMS - COLDS)
= 320.0 *ERROR(])
wh(4j)
The skin blood flow model described above, which is in(22) dependent o f time, was modified according to the work of
STRiC
= 117.0
.--
>O
The parameters WARMS and COLDS, together with the
head core ERROR value, ERROR(]), are substituted into
three control equations to determine the efferent command
signals:
= -5.0
44))
44j) =44j)
16
=
where STRIC is the vasoconstriction command, DILAT
is the vasodilation command, and SWEAT is the sweating
command. DILAT and STRlC are positive valued parameters used to calculate the deviation in blood flow from
the basal condition in the 16 skin elements:
CHARNY
<I al:
THERMAL hlOl>FL O F H A N DURING HYPERTHERMIA
local muscle temperature. but not in the same manner as
the skin blood flow model described in Section VI-A.
Muscle blood flow remains at a basal level until the local
muscle temperature reaches a “critical temperature” of
43 “C. Once above this temperature, the blood flow to the
muscle seems to increase linearly with time according to
the expression
wh(4j - 2) = wh(4j - 2)
+ B(fh)
- rO(4j- 2)) * rh
*(
(30)
- 2 ) - E((.)
* [Ter - T0(4j - 2)) * r.
* SWEAT * 2 . 0 E R R O R ‘ ~ i i I . * . O
C. Controlof Other Blood Flows
The blood flow rates to the core and fat layers of the 16
body segments are kept constant at the basal level during
the course of all simulations. Cardiac output is determined by summing all local perfusion values. Blood flow
to the thoracic core element is assumed to be equal to the
cardiac output.
VIL METABOLIC
SOURCEHEATING
The effect of local temperature on metabolic heating is
included in this model. Based on data from the literature
[15]. the rate of metabolic heating in an element is assumed to increase approximately 7 percent for every
0.5”C increase in temperature above the set point of the
following element
Qmet(;)
= Qh(i)
I
I ~07ERRORl,i/O.J
j ) )*
(32)
VIII. EVAPORATIVE
HEAT Loss TERM
Heat is transferred by evaporation from the 16 skin elements to the ambient air according to the thermoregulatory control equation f«r total sweating (see Section
VI-A). The rate of sneating is assumed to double forevery
1°C increase in local tsnipcraiurr ahwe the local set point
[SI
(H(j)
W
(3.1
where PSbnand P
., are the vapor pressures of water 11
mm H g at the skin and air temperatures, respcctivel/
which are functions of temperature and, in the case I):
ambient air, the relative humidity. In this model, seg
ments which are covered by the water bolus cannot lose
heat to the environment by evaporation of sweat.
Heat is also lost by evaporation of water from the lungs
(¡.e., thorax core element) to the ambient air. The evaliorative heat lost via this route depends on the ventilation
volume and vapor pressure of the ambient air. Mitchell
[16] relates ventilation volume to overall metabolic rate
as follows:
-M
* 0.0023 * (44 - Pa*)
(35)
where Elung
is the rate of respiratory heat transferred from
the lung in W , and Qmc,,body
is the total body m,?tabolic
rate in W , i.e.,
E-
=
Qmt.wy
64
Qmet.~y
off. The perfusion is held constant once the basal level is
reached.
(331
where SKINS (j)is próponional to the density of swra
glands in the skin element of segment “j. “ The heat Ics
from a skin element to the ambient air is limited by t:i,
following relationship [5]
.(31)
where r. is the elapsed tinie after the R F energy is turned
I
E(4j) = Eb(4j)+ SKINS (j)
E,, (4j) = (Pskln- Pur) * 2.14 *<
where wh is the perfusion to muscle in the RF-heated segment “j,”
B ( q , ) is an empirical factor, T,,is the critical
temperature, To is the steady-state temperature of the
heated muscle element prior to R F heating, and th is the
elapsed time after the RF energy is turned on. Upon increasing the blood flow to this heated region, the local
temperature drops and eventually falls below the critical
temperature. At this time, the muscle blood flow is held
constant at a new steady rate. w,. The resulting temperature profile is the “Type 11” response described by Roemer et al. [14].
Once the RF energy is turned off, the muscle blood flow
remains at the elevated rate w, until the muscle temperature falls below 39°C. The muscle perfusion subsequently
decreases with time according to the equation
wh(4j - 2 ) = w((4j
.5
=
Qml(i).
i-1
(36)
IX. EVAPORATIVESPRAY COOLING
Whole body cooling can be accomplished by spraying
the skin surface with water. The rate of evaporative cooling depends on the skin temperature and the air velocit;d
and temperature according to the expression:
EmY(i) = h, * SPRAY (A * S(j) * (P,ktn - P,)
(37 I
where h, is the evaporative cooling heat transfer coeffi .
cient in W/mm Hg m2 and S P R A Y (j)is the íiraction
of the segment surface area which is wetted. The heal
transfer coefficient was obtained from Cooney [17]:
.
h, = 14.7 *
> 0.50 m/s
11.2 * voZM u < 0.50m/s
v
h, =
where v is the air velocity in m/s.
(38)
(39)
X. PULMONARYHEATEXCHANGE
In the pulmonary system. the heat transferred ktween
the blood and lung is assumed to be governed by ani equation of the form
the cardiac output) and
ature.
Tungis the thoracic core ternper- the hone and
XI. METHODOF SOLUTION
The changes in tissue perfusion and heat lost by evaporation, both of which are dictated by the response of the
thermoregulatory model, are substituted into the governing heat balance equations ((1)-(4), (9)). Similarly, the
various heat transfer terms described in Sections 11-V, and
VII-X are substituted into the appropriate energy balance
expression. The coupled 65 first-order ordinary differential equations are solved for the temperature in each element as a function of time on a VAX’-I 1/750 computer
using a finite difference method of solution.
XII. RESULTS
A. Extremiry Heating
In order to evaluate the thermoregulation of skin blood
flow, immersion of the forearm in a hot air chamber was
simulated. It was necessary to use a nonzero value of 7 in
order to fit the experimental data of Johnson et al. [it?].
With r equal to zero an unrealistic response was obtained
as shown in Fig. 1.The change in skin blood flow upon
immersion was therefore recalculated with a nonzero value
of 7 and compared to the original, time independent model
and also to the experimental data of Johnson et al. (see
Fig. 1). Blood flows obtained with 7 set equal to 12 min
were in good agreement with the experimental data.
A simulation of the thigh heating experiments presented
by Sekins (131 was performed using the first-order skin
blood flow response and the muscle blood flow response
described in Section VI-B. Power of 200 W was deposited
into the thigh for one hour, starting at time zero. A& at
5°C was blown over the thigh during the heating period
as well as IO minutes prior to heating (not shown) in order
to match the conditions of the experiments. The energy
was subdivided into four tissue layers according to the
theoretical method described in Section V. The muscle
temperature and blood flow predicted by the thermal
model are represented by the solid lines in Fig. 2. Inspection of Fig. 2 reveals that good agreement is found
between the numerical predictions and experimental data
when 6 is kept constant at 1.0 ml/minz/ 100g/OC. Experimental data were not available for the time after 20
min of heating due to limitations of the Xet3’ washout
technique employed by Sekins 1131.
Figs. 3 and 4 display the temperature profiles within a
lower leg during simulations of MAPA exposure. Power
of 200 W is deposited into the lower leg at time zero. This
energy is subdivided into the four tissue layers in two
manners: according to the volume-conductivity product
weighing described in Section V, and based on experimental data. Experiments by Charny et al. [I91 measured
the time rate of temperature rise in an amputated human
leg during RF-induced hyperthermia. The specific absorption rate (SAR) values calculated from these data revealed that 14 percent of the total deposited energy is in
IO percent is in the fat. The energy depositions computed by the two methods are Compared in Table
11. The rate of blood flow to the hone. which is not under
thermoregulatory control. is based on t w o different literature values IS), 171. In these simulations. the leg is surrounded by a 25°C water bolus which is built into the
MAPA. The water bolus is removed from the lower leg
surface at the end of the one hour heating period. The
ambient air is at 30°C. O. 1 m /s velocity, and 20 percent
relative humidity.
Fig. 5 shows the effect of lower leg MAPA exposure
on whole body parameters given the conditions of Fig.
3(a). The whole body response is similar for all four of
the cases shown in Figs. 3 and 4. In these simulations,
the RF energy is deposited only into the lower leg segment. Based on the calculations of a three-dimensional
block model of man [ 1I]. there is some aberrant energy
deposition during MAPA exposure of the lower leg,
mostly in the thigh and foot of the treated leg. However,
this aberrant energy deposition does not significantly
change the whole body response to MAPA exposure.
B. Abdomen
Hearing
Hyperthermia treatments in the abdomen were simulated via a IO00 W deposition into the abdomen segment.
This power was subdivided within the abdomen layers by
the VS product weighing method. Fig. 6 displays the
whole body response to APA exposure without evaporative spray cooling. The simulations shown in Fig. 7 calculate these parameters when the patient’s limbs are
sprayed with water during the heating period. As in the
case of lower leg heating, the power was turned on at time
zero and turned off after one hour. In Figs. 6(a) and 7(a)
the ambient air velocity is 0.6 m/s. In Figs. 6(b) and 7(b)
the air velocity is 1.0 m/s. Air flow can be maintained
at this high velocity by a 12-inch diameter fan blowing
150 cubic feet/min.
Based on the three-dimensional block model of man
[ i l l , RF energy directed at the abdomen with an APA
operating at 70 MHz will be deposited into the body segments in the relative amounts shown in Table Iii. The
effect of this aberrant energy distribution pattern on whole
body parameters is shown in Figs. 8 and 9. In Fig. 8,
there is no spray cooling, while in Fig. 9 the. patient’s
limbs are sprayed with water during the heating period.
The air velocity is 0.6 m / s in Figs. 8(a) and 9(a), and
1.0 m / s in Figs. 8@) and 9(b). In all of the simulations
of APA exposure the abdomen is surrounded by a 25°C
water bolus, which is removed from the abdomen surface
after the heating period. The air temperature is 30°C and
relative humidity at 10 percent.
Previous repons by the authors investigated the effect
of applying ice packs on the extremities during APA exposure [20]. Results from the current version of this thermal model show that the evaporative spray cooling method
is a more effective modality for reducing the extent of
systemic heating.
_"
381
c H + R ? i Y <I ril T H F R U A L MODEL OF MAN DURING HYPERTHERMIA
Skin BF Response t o Immersion
30
n.o
I
A
A
11.5
15..
12.5
I...
1.5
C
Y
v>
5.0
...
2.5
0
I
I
I
I
I
1.
2c
J.
4e
W
W
Time ( m i n )
Fig. I . Thwrcticai calculations of forcam skin b l d Raw rcsponsc to hot
air exposure with a zero and nonzero lime constant. Expcnmentll dam
are fmm Johnson [IS].
Muscle Blood Flow Response,to 200
4a
44
-u
P
E
41
4.
0
t-
3.
I
o I .V?. ?rp
30
lime (mini
1
200 U To Lower Leg w/theo O r f
w
280 U To Lower Log wiexpt O r f
I
86
Y
.
I
I
I
I*
n
Y
I
u
I
I
w
w
I
1
1 . 8 8
I
a.
(2)
-O
:
EEz3
Y O
I
e
2
e
Y
U
W
O
.
1
1
.
8
0
R
TIme ( n i n )
n
E
O
I-
u
o
I
I
18
2e
I
Y
I
I
I
u
w
O.
I
I
w
1
R
TIme (min )
(b)
(bi
Fig. 3. Tl~eorctic.l calculations of tempsnturc profiles within a lower leg
exposed to 200 W via the MAPA applicator. The power is sobdivided
into the four layers by the V-S weighing method of Section V. (a) Bone
blwd flow is zem [71. (b)Bone blood flow is 0 . 6 5 mi/min/ 1Wg [SI.
Fig. 4. S a m conditions as Fig. 3 extcpi power subdivided according to
expnmenul rrsultr 1191. (a) Bone blood Row ir zcm and (b)bone blwd
Raw isO.65 ml/min/100g.
XIII. DISCUSSION
The whole body thermal model presented here is most
useful for comparing the effectiveness of various surface
cooling conditions to reduce the adverse effects of systemic heating, namely elevated cardiac output and local
temperatures. Due to the lumped nature of the model, regional averages are calculated rather than exact “hot
spots.” Given this limitation, there are certain trends
which are evident.
In the case of lower leg heating, the extent of systemic
heating is slight. Core and brain temperatures increase less
than 1°C during the one-hour heating penod. The thermoregulatory system causes an increase in blood flow to
the muscle and skin regions o f the leg. These perfusion
changes result in a 30 percent increase in cardiac output
above the basal level. Whole body sweating an changes
in skin blood flow also act to dissipate the heat. hus, the
thermal response of an extremity to regional heating is
controlled not only by local thermoregulatory mecha-
4
nisms but also by central thermoregulation. Thermal
modeling of an isolated leg neglects the significant effects
of hypothalamic feedback control.
The average temperature of the muscle element is approximately 41.5% which is slightly below the therapeutic range for hyperthermia. Considering the lumped
construction of the model, this result indicates that therapeutic heating of a tumor within the lower leg can be
accomplished but there may he some elevation in the temperature of the surrounding normal tissue.
Since block model calculations have not been able to
provide sufficient detail we have estimated the division of
energy deposition into the four tissue layers by assuming
that the electric field within the MAPA applicator is parallel to the tissue interfaces. According to boundary relations, the tangential component of the electric field is
necessarily conserved across the tissue boundary. Thus,
the SAR in each region is proponional to the electrical
conductivity of the tissue. Under these conditions, only 4
W of the total 200 W assumed deposited into the leg are
THARNY
II
0 1 THERMAL MODEL OF MAN DURING HYPERTHERMtA
TABLE II
COMPARISON OF THE E'IEROI
DiSTRtBUTtON WITHIS A LOWER
LEG
CALCULATED B Y THE METHOD
IN S t X T I O i v AND OBTUSED BY EXPERIMENT
-
Percent energy inlo leo_tissue
by V-S product weighing
Percent energy into leg
tissue fmm a p t .
2.0
90.5
2.5
76.0
bone
muscle
fat
skin
14.0
I...
5.0
--E
\
10.0
IS..
-
I*..
I...
o)
L
Q
+
7..
..
Nhole Body Response t o 260 U Leg Heating
I..
e
LL
U
o
O
Y
o
.
a
E
W I
m
I-
1 . 2 .
w
u
m
e4
TI
e*
m..-
o.
Tlne lrnin)
Fig. S. Calculations of whole body response IO 200 W lower leg heating.
actually deposited in the bone. Yet this assumption still
results in a notable increase in bone temperature to 4243°C (Fig. 3(a)). The effect of nonzero bone blood flow
is to decrease the maximum tempe ture in this region by
approximately 1°C (Fig. 3(b)).+
Experimental results obtained from studies with amputated human leg "phantoms" [I91 have shown that the
deposition in bone is significantly greater than what would
be found if the electric field were parallel to the tissue
interfaces. When the thermal model is used with the experimental values o f energy deposition, the calculated
temperature profiles are quite diffeent. Assuming zero
bone blood flow results in a maximum bone temperature
of 62°C (Fig. 4(a)). Given a perfusion of 0.65 ml/
min/ 10g. the bone is still heated to a maximum of 57°C
Fig. 4(b)).
-These calculations reveal that the bone temperature may
significantly elevated during MAPA exposure. Again.
the limitations of thi. model must be emphasircd. The
7
6,
Tine ( i i n )
(b)
Fig. 6. Calculations of whole body response to loo0W abdomen heating
with no spray Cwting. Cd Air velocity PI 0.6 m/s. (b) Air at I .O m/s.
bone temperature is most likely not spatially uniform. This
tissue is heterogeneous in composition and its thermal and
electrical conduction properties are anisotropic. However, localized "hot spots" o f elevated temperature may
exist inside the bone which approach those predicted by
the thermal model. Due to patient considerations, it is not
possible to monitor bone temperatures during a clinical
hyperthermia treatment. But experiments with the unperfused amputated leg phantoms measured similar bone
temperature increases for a power deposition of 200 W.
It should be noted that rJdially shifting the leg a w a y from
,
u ,
hcsd
ncck
tho=
-
sbdomcn
upper arms
forearms
hands
upper legs
lower legs
feet
o.
E
o
I-
x
1
~
111
1-
N-1 I Y I
1
1
I
--
-..
L
o
I.
CL
*....
E
o
g
...
...
...
1..
I-
e."
---
a
+
Ih.
b.
..
I
t
c<-
e
I.
m
m
-
n
.L
~e
Y
-
0
o
O
..-
4
A
I
Tine (nini
*-
(b)
Fig. 7. Same conditions as Fig. 6, b
u
t with spray cooling. (a) Air velocity
*-
0.6m/s. @)Airat I.Om/s.
rY
~
..'
I
P
c
-
,...
.
the central axis of the MAPA reduced the energy deposition in the bone by over 60 percent [19].The maximum
bone temperature under these conditions would be reduced from 61.6-Cto 49.3-C for the case of zero bone
blood flow and from 57.0"C to 47.0DCfor the case of
nonzero bone blood flow.Two cases of abdomen eating were considered: the
deposition of loo0 W into the abdomen core element only,
and the deposition of loo0 W into the whole body, which
was distributed according to the data in Table 111. In both
cases, systemic heating was found to be significant. Figs.
6-9 reveal that high-velocity air flow (1.0 m / s ) coupled
R
2.0
1.o
20.0
37.0
14.0
5.5
I .5
18.0
0.8
0.2
with external application of water spray on the patient's
limbs are helpful in controlling the increase in cardiac
output that occurs during abdomen heating. However,
thorax core and brain temperatures initially rise to high
levels in both cases. Without aberrant heating (Figs. 6 and
7 ) , these regions cool off by several degrees after approximately 15min of RF heating when sweating becomes the
principal mechanism for heat loss. When aberrant heating
is assumed (Figs. 8 and 9).evaporative spray cooling with
high-velocity air flow is effective in keeping the calculated brain temperature below 40°C.
As shown in Figs. 6-9,evaporative spray cooling removes up to 200 W of energy, which is about 10 times
the energy that can be transferred to a circulating water
bolus around the abdomen. Exposure to high-velocity air
flow during evaporative spray cooling appears to be the
most effective cooling modality. Simulations in which the
patient is exposed to these surface conditions prior to
heating indicate that precooling does not affect the extent
of systemic heating.
The assumption of 1 kW deposition directly into the
abdomen core increases the regional temperature to 42Mac, depending on the cooling conditions. When aberrant heating is assumed, the abdomen core reaches a maximum in the 40-42OC range. These results indicate that
treatment of a tumor in the abdomen core with an APA
applicator may significantly elevate the normal tissue
temperature in this region. The effect of the aberrant energy deposited into the other body segments, such as the
neck, upper arms, and thighs was to increase the average
temperature in these body segments above 40°C. even
with spray cooling and high-velocity air flow conditions
(see Fig. IO).
It must be noted that these numerical results could not
be compared directly to measurements made during clinical hyperthermia treatments. There is little published
quantitative data on whole body effects during regional
hyperthermia. The core temperaures cdculated for abdomen exposure to the APA applicator are. however, in
good general agreement with those of others 131.141. Similarly, the muscle temperatures calculated for lower leg
exposure to the MAPA applicator agree with published
*
CHARNY
CI
01 THERMAL MODEL OF M A N DURING HYPERTHERMIA
..
-t
I
385
a,.-
j -F
--11..
.*
I...
O
.,
Q
u
I
E
O
I-
I..
I...
,___.
...-
rn
1..
a
*..
n
t..
a
o..
m
L
O
t
-*
O
Li.
0
o
O
<II
Tlae ( m i n i
(b)
Fig. 8. Calculaliona of whole body Esponse 10 Iüüü W healing with aberrant deposition and no SPRY cooling. (a) Air velocity
0.6 m/s. íb) Airs1 i m/s.
. .<
1
c
m
I
'a
U
t
It..
I...
-re-------\
____.___...
.-._.--..
................
I
I
I
I
I
1
<"I
h
i
or1 <I1
I
I
I
8
-t
-g
._____
...".
.._
..
1
M
1..
'.., \
rir
dnn
,.-
u -u
--
1
.
1
1..
L
I..
TI
o
O
d
Fig. 9 . Sime conditions as Fig. 8. but with 'pray cooling. (a) Air veloeity 0.6 m/s. (b) Air ai I m/s.
clinical results [21]. We are pursuing collaborative work
which will be necessary to further validate the results of
this model.
CONCLUSIONS
Results from this study show that the aberrant energy
that is distributed throughout the body by an APA applicator will cause significant systemic heating. The best
conditions for limiting t h c estent of the systemic heating
are evapontive spny cooling with water on the patient's
limbs and exposure to high-velocity ambient air. Under
these conditions. the calculated cardiac output during an
RF exposure of 1 kW is increased to a value approximately 2.5 times the basal level. While brain and thoracic
core temperatures remain below 40°C during the treatment, the average temperatures in the neck. upper arms
and lower arms exceed 40°C. Simulations of exposure of
the lower leg to a MAPA applicator indicate that then is
negligible systematic heating. but the effect of energ)
deposition in thc hone is potcntiall) dangcroii\
I
lEFt THA<SACTI<>NS
386
“
.
Average Temps w i t h No Aberrant Hea,t
O V LlIOM1~1~IC4L
F I G I I F F R I S G . \O1
RUI: U NO J ‘!*Y
lVS7
Average Temps wlth Aberrant Heat
I.
- U
n
E
0 3 s
I-
.-.
__.,---
r----__
_--.-.--._________
,,-,.......__...-...-r
_-_-_-_I.
n
Fig. IO. Calculated average tempcratures in three segments under the conditions of(sj Fig. 7 @). Fig. 9@).
ACKNOWLEDGMENT
The authors thank Dr.J.-L.Guerquin-Kern for many
helpful discussions about whole body heat transfer and
the related physiological effects.
1141 R. B. Roemer. 1. R. Oleson. and T . C. Cetis. “Oscillatory iemperature response 10 constant power applied to canine muscle.” Aner.
J. Physiol.. vol. 249. pp. R153-RIS8. 1985.
[IS] R. L. Levin, and M.I. Hagmann. “A heat and mass transfer model
for computing thermal dose during hyperthermic lrealmnl of extremities,” in 1981 Advances in Biocn#inrrrin#.R. L. Spilkcr Ed. New
York: Amer. Sac. Mcch. Eng., 1984. pp. 13-14.
(161 J . W. Mitchell. E. R . Nadcl, and 1. A. 1. Stolwijk. “Response io
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I21 P . F. Tumer, BSD Medical Corporaiion Hyperthermia Tech. Note 1
17 D. O. Cwoey, Biomedicol Enginruing Principlcr. New Yo&
12, Snit Lake City, UT, Aug. 1985.
Marcel-Dekker. 1976, pp. 114-117.
I31 B. Emami. C. Perez, G. Nussbaum, and L. Leybovich. “Regional [I81 I. M. Johnson, O. L. Brenglemann. and L.B. Rowell. “lnienctions
hyperthermia in treatment of rccumnt deep-seated NmOrs pdimik w m lofnl and reflex influences on human forcam skin blood Row,
nary repon.” in Hyprnhennio Oncology 1984. Vol. I . 1. Ovcgaird
J. Appl. Phys.. vol. 41, no.6. pp. 826-831. 1976.
Ed. Lnndon: Tiylorand Francis. 1985. pp. M)S-M)8.
[IS] C . K. C h y . 1. L. Guequin-Kern. M. 1. Hagmnn, S. W.Levin.
141 F. A. Gibbs, M. D.Saporink, K. S. Gates, and 1. R. Stcwan. “ReE. E. Lack, W. F. Sindelir. A. Zibell. E. Glatstein. and R. L. k v i n .
gional hypenhennis with an mnuluphased n m y in ihc expcrimnul
“Humin leg heating using a mini-annular phiwd amy.” Mtd. Phw.,
treatment of cancer;’ IEEE Trans. Biomcd. En&. vol. BME-31, pp.
vol. 13, pp. 449-456.luly/Aug. 1986.
115-119. Jan. 1984.
[201 C. K. Charny, R. L. Levin. M. 1. H a p a r m . and E. Glatstcin.
151 I. A . 1. Stolwijk and I. D. Hardy, “Control of M y temperature.”
“Whole boay thermal model of man during hypnhermia,” in Pim.
in Handbook of Physiolop-Reocrions Io Enrironmrnral A ~ ~ D.
I s ,
Nonh American Hypenhrrmia Group Ann. Mrer., 198%
H . K. Lee Ed. Belhesda, MD:Amcr. Physiol. Soc.. 1977. pp. 461211 1. R. Olesan and 1. M. Hamlsan. “Preoperativehypnhermii and
67.
radiotherapy for extremity samma: Initial msults.” in Pmc. Nonh
161 E.H.Wissler. “Mathematical simulation of human thermal behavior
American Hypcnhennia Croup Ann. Mcn.. 1986.
using whole-bcdy models.” in Hear Transfer in Medicine and Bid- 1221 1. R. Olesan and 1. M. Himlson. “Pmopraiive hyprrherrnia and
op. A. Shitzer and R. C. Eberhnn Eds. New York: Plaum, 1985,
radiothcnpy for extremity s1rcom: Initial rcsultr.” in Pror. Nonh
pp. 325-373.
American Hypcnhennio Croup Ann. Men., 1986.
171 R. O. Gordon. R. B. Racmer, and S. M. Hoivath. “A mathematicd
model of the human tcmpcratun regulatory system-transient cold
exposure response.” lEEE Trans. Biomed. Eng...vol. BME-23, pp.
443-449. Nov. 1976.
I81 1. A. 1.Siolwijk. “Whole body heating-thermoregulation and modeling.“ in Physical Aspcm of Hypenhrnnia, G. Nussbaum cd. New
Yo*: American Insi. Phys.. 1982, pp. 565-586.
191 R. 1. Spiegel, D.M. Lkffcnbiugh. and I. E. Mann, “A thermal model
o f the human body cxposed to an electromagnetic field.” Bioelerrromag., vol. I , pp. 233-270. 1980.
I101 W. I. Way. H . Kritikos. and H. Schwan. “Thermoregulatory physCnleb K. Charny was horn in While Plains. N Y
iological responses in the human body exposed to microwave radiain 1961. H e received thc B.S. dcgree summa cum
tion,” Biorlerrromag.. val. 2, pp. 341-356. 1981.
laude in chemical cnginccring from the State UniIll1 M. 1. Hagmann and R. L. Levin, “Aberrant heating-a problem in
versity o f N c w Yo&. Buñalo. in 1983.
regional hypcnhemia.” IEEE Tranr.’Eiomcd. Eng., vol. BME-33.
He is presently a cundidate for the Ph.D. dcpp. 405-411. APT.1986.
gm in biomedical cnginccring at The Johns Hop
1121 M.A . StvehlY and S. S. Stuchly, “Dielcciric propcniesofbiological
kins University School of Medicine. Baliimorr.
subsiancc~-tabulated,“ J. Microwave Power, vol. 15. pp. 19-26,
MD. His thesis rercnri-h is on regional and whole
Jan. 1980.
body heat trannfcr.
1171 K . M . Serins, “Microwave hypenhcmia in human muscle,” Ph.D.
Mr.Charny was n mdpicnt ofthe 1980 Kodak
disrcnaiion. Univ. Washington. Seattle. 1981.
Scholars Award.
L
-HARM n al: THERMAL MODEL OF MAN Dqai\ I IHYP
i
-
rL
p'"
.
t
I
387
1mplicr:tion of Blood Flow in Hypei-thermic Treatment
of 7'urnors
!
lishmciit aid Inigressive growth of malignant tum , x s is pilsjiiile w ! m thc supply of e s x : n t d nutrients is adeqiU.tely nlsintaineil t u o y h v ~ c u l anetworks.
~
The morpho1oy;c;il chi.;icreristics o f i a s d a r bed and the olood tlow in
tuniors ha\: :>em itudiei b) a number o f investigators [ I S ] [ZO] . h i 115 tte uiitid stage of tumor growth, the tumor Cells
ar: sapporrcl by the nutrierits supplied from the host m u l a turz. As tli: :ulnar mass iricieases, the adjacent venules(srnd
hmt iis'ues hecome dilated and tortuous. Subsecnilotitelial CEUS (cells that make up the inner part
of'Zaviileh :f h:ooil v e s s l j ) &ifthe altered host venules start to
prdifeiatt:. perhaps J ) die influence o f angiogenesis factors
(substaices which stimuiete tiie development arid growth of
hlcoii vewlh:, froin the tumor cells as described by Folkman et xi. [21] and othcr investigators [2?]. Numerous
sprouts g i w out of the hypertrophic venulesandgrow towards
the tumi~r Tbe sprouts or their brariches eventually fuse,
giving Bsc l o I ~ ~ o p sThe
. grcwing sprouts or caiiillaries penetrate iiit<i ihe periphery of tumor and anastomose with the
aiiteriot eriti of host capillaries, and then blooa begins t o perfuse tluoudi Ihe new vessels. Although most of the new
capillades in tumors appear t o form from host venules as
described .i')ov.:, necv;isciilarizations may also be possible at
the artwioli.r site of host c:apillaries.
It is gs:,ieraily helievecl that the vascular pattern is characterirtic for : x I i type o f tumor, although striking variations in
the vaIcu1í.i pa:teriis can he seen, depending o n the stageof tumor grow t in the siime type o f tumor. As the tumor mass increases, 111 irc tumor capillaries are formed and elongated. The
hastily for iicd new tumor capillaries consist o f a singlelayered
endotlsha. wall wiih no external basement membruie. in
niany tyl1i.r of tumors, tha vessels are a sinusoidal type (a form
of thui-u;died blood channel with irregular sh:ipe) with interrupted lin:iig of endothelial cells. Between th,: gaps ofendothelid cells, neoplastic cells often protrude into the hIBen o f
car>&iiies :.rid obstruct the perfusion o f blood. I t has been ob-
:
.
-''
tic.ularly in the large undifferentiated tumors. One of the other
striking features of the tumor vascular network is the prerenu:
of to~tuous,giant capillaries, as large as 50 pm in diameter.
. The wall o f such vessels is composed only of endothelial cells
with some fibrous supporting tissues. These vessels are usually
'- located at the periphery o f tumors and contain venous blood.
these vessels may be considered as venous capillaries.
-- Thus,
Arterior-venous shunt is also a common feature o f tumor
vasculature pattern. Occasionally, matured vessels are found in
tumors, particularly in the slowly growing and highly differentiated tumors. These vessels are composed of intact and
complete endothelial linings with normal basement membranes
rand are supported by fme strands of collagen fibers.
It should be noted that not all tumor vessels are newly
formed vessels. It is of interest that the host vessels are resistF- ant to neoplastic growth and are rarely invaded by the tumor
cells, but often are incorporated into the tumor mass 1231,
[24]-[26]. The incorporated host vessels do not increase in
-number, although the length and caliber may increase. Portions of such host vessels incorporated into the tumors eventually disintegrate together with the tumor vessels, particularly
in the necrotic area of the tumors.
YIn summary, the vascular network of tumors is rather different from that of normal tissues and consists of: I) capillary
sprouts, 2) sinusoidal vessels with interrupted endothelial linr i n g , 3) blood channels without organized endothelial lining, 4)
$ant capillaries, 5) matured capillaries with basement mem-branes, and 6) host vessels. The relative proportion o f the
above components in each tumor Is characteristic of the tumor
c
ype as well as the stage of tumor growth.
I
...
I
F
,
!
.
Skin
16'c
~
-
-
-
-
FS 2. Cha
water bit
the use 0
Heating t i m e (min)
1. Changes in blood flow in the skin of SD rats huid with wale
bath. The blwd flow meanired at the snd of heatingwith the ux D
radioactive microsphsrei. The average and SE. of 8-12, meesun
muairem
Fip.
,,, the skin
1361 -1391.
ments PIC shown.
nounctd ch
It43Y
un md Ip
tively. At 1
I
.-
BLOOD F m
IN
TUMORS
Once the tumor vascular network is established and blood
tarts to flow into the tumor from the host arteries, the mass
of tumor increases progressively. As mentioned earlier, the
.number of host arteries or arterioles seldom grows, whüc the
umber and length of tumor capillaries fed by the m e host
-arteries increase as the tumor grows. Such an increase in the
capnetwork and an increase in the demand for blood in
'-:cess o f the capacity of host arterioles would result in a deh e of arteriolar pressure. At the same time, the extravasu.
lar pressure in the tumor increases as a result of the prolifera*n of tumor cells within a limited space. An increase in the
I travascular pressure exceeding the arteriolar pressure results
iíiregional vascular stask and necrosis. The limitation o f diffus$n length of oxygen and possibly other nutrients is believed
be another cause of necrosis in the tumors (27).
'L-Whether the blood flow in tumors is smaller or larger than
that in normal tissues has been an enduring question. It has
I n been suggested that the blood flow through the inegul b constricted, dilated, and twisted vascular network in tumors is sluggish and retarded as compared to the blood flow in
t h - normal tissues. It should be emphasized that the blood
fll Iin tumors vanes with the type of tumor and the stage o f
tukor growth or size oflumors. Furthermore, the distribution
of blood perfusion in the tumors is quite inhomogeneous. Usuad- the blood flow i n the well-vascularized peripheral area is
p d e r than that in the inner area of the tumors [24J. The
-
I
P
reported blood flow in various tumors and normal tissue
varies enormously [ 191. We observed that the blood flow ii
the skin and m u d e of SD rats was 7-8 d / I O O gimin an
4 5 ml/iOO g/min, respectively (Figs. 1 and 2). The blwi
flow in the 0.3-0.7 g of Walker tumors of SD rats was abou
50 ml/iOO s/min, whereas that in the 2-5 g tumors was onl:
10 ml/lOO dmin (91, [281. The tumor blood flow in th'
spontaneous mammary carcinoma of the moux was onl!
1-17 ml/iOO %min [IS], 1291, while the blood flow in th
outer side of lymphosarcoma of the dog was as large as 1831
ml/iOO g/min and that in the inner part of the tumor wa
121 ml/iOO &in
(301. In this context, the blood flov
in lymphoid tumors appears to be relatively larger than tha
in other types o f tumors. For example, the blood flow in thi
lymphoma of the human was 38.4 ml/ioO gimin, while thi
in the anaplastic carcinoma of the human was 11.4 ml/lM
g/min (311. The blood flow in the Novikoff hepatoma of th~
rat was 2-5 ml/iOO g/min and that in the normal liver wa
80 ml/lOO dmin in the rat [32] or 47-120 ml/lM) dmin ii
the dog [33], [34]. In humans, the blood flow in a liver car
cinoma was 12 ml/lOO &in, while that in the normal live
was 29 ml/IOO dmin [35]. It appears that the blood flow ii
the neoplastic tissues is generally smaller than that in the cor
responding normal tissues, although ample exceptions ma)
exist.
v-u~R
By ~
y
~t
The most commonly used normal tissues to study the e:
fect of heat on vascular function have been the skin and mu!
cle mainly because it is relatively easy to heat those tissues an
to measure their blood flow. We have investigated the c h a n ~ e
in the blood flow, vascular volume, and vascular permeabilit,
&fold in d
kidiute thi
heating.
The ped
auad,
in F
nu was 7
&Owl
101.0 mlll
4S0C fa
the rkin SU
31.5 d/10
about 4.fol
blwd flow
lt
heltUig con
blwd flow
though the
was still sbc
120 min. H
h e skin bla
oí OUI rnves
minat43'~
Thc bloo
nun (Fig. 2,
c i t a d to
R
~
value. al 30
and 10 alnw
uvely. The i
uhich was t
L
1
'
~
11
44OC.
Ur
the muscle I
4 4 O C for up
11
rlrii 11 icr~::ise .I 1 . t.cwd !lo\< . , I tlii I1 1 ~ ~ 1I C,: : IZí :'I I.
.~\bc~iit
! . j . f i ~ l.i o c .~E r the r n u i e blt <
i t!w,,
i
( i t s ~h \ I { : d
after ile:itiig at 4:)'
i o i cui) rriiii.
<) >bseivib iiai the hloodíluu ,:. ::le $.:P. 2nd i" i i ~ e
of riie 1'isc;ier rlt 1:.iezsed by 9.fold it) i>i Iifztiiig at 41.5%
for 1 1 i :4(i], l)i.l:$,: et al [ d i / reFu:ts I :
I? ü - i ' ~ . iir.arz.iw ir
blood flou in the $
2 n d a 1 0 i o i ~ l~I.,C,.:J;P U,t..ood ti. '.I
the re)iiluaJ t i s i e s . : *e foot of die \ V . j t ~ i rrar iipon hL,.iriiie
at 4 1 y fcr 1 h Tkr &ive obsarva:icir: . i f ?O-fold inarexv3 ..I
the sloii blood :law A t -U"Cis strikiiirl:,,;;:eater tliari tiir ircrease,in the b i o a ~f h v we obserred in the skin o f S1) 01
Fisclier rats Iieated:;~~
43 O or 43.SoC as d:scriberi above. D i i i son eta/. [41] fiirtl.cr re?urted that the tlood flow in thc s k i t
of Wistar rats stxtati IO ,.lecrease aitcr he.itirig for I h a t J?"':,
while w e observea vu de:line in blot>d flow in the skim vf Sí)
rats after heatin: tkr 2 !i at 43'C (Fig. I). Steviart and Ileg,,:
1421 ~&orted that heatine at 42.5'C f i i r I h iriireaseil the
12
JEEZ TRANSACilClNSON LIlOMEDlCALfN<iI~E>.XING.
VOL. E M F 3 I . N O I . JAIII'hRY
1 9 1 ~
the blood flow in Walker tumors heated at 43'C was similar vascular damage and hemonhagewere ohserved afirr heating ; I
to that in the tumors at norniothermic condition.
43'C. Endrich er ai. (541 measured the velociiy of KBC's in it,:
The blood flow in certain types of tumors appears to in- rhabdomyosarcoma grown in the transparent chambers in rat!.
crease, at least temporariiy, upon heating at relatively low !em- When the tumors were heated at 40*C or higher temperaturei,
peratures. Sutton er aL 1461 and Bicher et aL (471 reported the velocity o f RBC'$through the capillaries steadily declined
that the blood flow in mouse tumors increased upon heating Stasis and petechial hemorrhage in venules and capillarier oc.
at temperatures up to 41-42OC for 30-40 min, but decreased furred when heating was continued, resulting in a decreare ~fi
when the heating was prolonged or the temperature was raised. the number of perfused capiliaries. The circulatory damage by
Vaupei er al. [48] also reported that heating at 43°C for 20 heating at 4042'C for 60 min was apparently irreversible. A
min or at 44-C for 15 min increased blood flow by 5-100 similar transparent chamber device was used by Reinhold er a¿
perceni in 60 percent of DS carcinosarcoma o f the rat. Further [SS] in their study o f heat effect on the circulation in the
heating caused cessation o f blood flow in these tumors. In 30 rhabdomyosarcoma of the rat. Impairment of microcirculation
percent of tumors studied, the blood flow decreased from the accompanied by severe necrosis was observed following heat.
beginning of hyperthermia, while no significant change m ing at 42'C for 3 h or at 42.5OC for 162 min. Dudar and I&
blood flow occurred in the remaining 5 percent of tumors. In I441 studied the heat-induced vascular changes in VX2 car.
the same DS tumor, blood flow was found to be impaired cinoma grown in a rabbit ear chamber. Both the RBC velocity
upon heating at 42.5OC for 100 min by Van Ardenne et al, and the total blood flow slightly increased when heated at
1491. Stewart and Begg 1421 reported that the blood flow in 42.S'C. Such an increase, however, lasted only for 10 min, and
the tumors of the SAFA mouse increased slightly during the the vessels were completely occluded thereafter. Table I Jiows
first 30 min of heating at 42.5'C. returned to control level the heat d w which induces vascular damage accompanied by
by the end of heating for 1h, and significantly decreased 1-2 a decrease in blood flow in various experimental tumors stud.
days after heating. These investigators also reported that a ied.
similu decrease in blood flow occurred 1-2 days after heating in three other mouse tumors. Rappaport and Song [40]
ROLEor BLOOD FLOWIN THERMOREGULATION
observed a slight increase in blood flow at the end of I h heatAs described in the preceding sections, the results to date
ing at 43.S°C in mammary carcinoma o f the Fischer rat. The indicate that the response of vasculature in tumors and normd
blood flow, however, drastically decreased 1-24 h after heat- tissues to heat stress is markedly different. The reported dab
in& Dickson and Caldenvood I411 noticed that the blood on the response o f vasculature in tumors and normal tissuts 10
flow in the Yoshida sarcoma grown in the foot of rats did not heating can be graphically compiled 89 shown in Fig. 3. Upon
change significantly during heating at 42'C for 1h. The tumor heating at 41-43OC, temperatures commonly used in clinical
blood flow, however, decreased when the heating was pro- hyperthermia, the tumor blood flow either undergoes no sip
longed for more than 1h. It was of interest that the tumor nificant change or s l i t l v increases. uuiallv
smaller
than 2.
-<
blood flow feu almost to zero when measured 1 h after heat. fold. Indications are that ;he tumor v&kature is quite vulner.
ing at 42OC for 1h, and then gradually returned to the pre- able to heat so that severe vascular stasis. occlusion, and hemheating level 12 h later. The effect of heat on the vasculature orrhage are prone to develop at 42-43'C, at least in experic and blood flow in the BA-1 112tumor grownsubcutaneousiyin mental animal tumors. In contrast, the blood flow in normal
the scalp of the rat was studied by Emami er d [50]. About tissues, e.g., Uwi and muscle of rats. markedly increases upon
*- a SO percent reduction in the blood flow occuned after heat- heating by as large as 20-fold. Although the heat.induced in.
ing for 40 and 30 min at 41 and 42OC, respectively. More pro- crease in skin and muscle blood flow starts to subside after
c
nounced and long-lasting reduction in blood flow occuned heating at 4445°C for 30 min, complete vascular stasis ap
,. when heated at 43 or 44'C.
We observed that the functional 'pears to occur after heafug with much greater heat dose (Figs.
intravascular volume in the SCK tumor o f the mouse progres. 1and 2). The magnitude of increase in blood flow by heat in
sively decreased for several hours after heating for 30 min at different organs may be different, The ratio of blood flow at
41-44OC and began to recover from 1day post-heating [9], resting stage and the maximum blood flow in different organs
[ 131. [Si], (521. Histopathologic examinations o f the heated of human is known to vary considerably 156).
,SCK tumors indicated congestion o f vessels with blood ceUs,
According to the bioheat transfer equation [IO) -[12], the
stasis, occlusion, and hemorrhage.
differential response of blood vessels in tumors and normal tis
--The tumors grown in transparent chambers have been used sues would greatly affect the temperature distribution during
to
investigate the heat-induced vascular changes by other in- hyperthermia. Guy er aL 157) graphically showed that tumor
,-vestigators.
In squamous carcinoma grown in the transplant temperature would rise higher than normal tissue temperature
dhambers in the cheek pouch of hamsten, Eddy ef uL [53] when the blood flow in normal tissue is preferentially innoticed temporal vasoconstriction during the first several sec- creased. so that the blood flow in the normal tissue become
l n d s of heating at 41-4S°C, followed by a dilation. During greater than that in the tumor.
Fig. 4 shows our representative observations on tempera.
-*ieating at 42'F for 30 min, parts of a few vessels became
static. When examined 1-24 h after heating, relatively mild ture changes in the Walker tumor 256 grown S.C. in the leg of
&asis, diapedesis (passage of blood corpuscles through intact SD rats and that in the muscle adjacent to the tumors (391.
esse1 walls), and petechiae (a minute red spot caused by an The heating was applied with a water bath at various tempera%cape of a small amount o f blood) were evident. More severe tures. I t can be seen that the muscle temperature rose rapidly
,picC!
a
2
-
.
..-
a
Fb. 3.
R
and thr
icmpn
dati Io,
tumors
I
.
Chi
or SD n
118 4.
at lempo
with 11
Reprcn:
\iii . 9 :
ti;: 1:::
tl¿i
il"
4:!.0"('/30 ri J j
4:!.5"<'/40 ri 1
arid then declined si&$fic.intb? within sev. $al minutes of heat..
ing at 424i'S. A p x 4 nily, die blood So ;;inthe heated mu,..
c k increased ar d ffii.4 the rote of heat dii $ationwas acoelcr..
ated, resultiiig in ffie (licreaie in tempera.)re. The higher tl:e
teniperature iisi!d, %e ioiinvr the declini ti tanperature c,i:..
curre(:, inG:atiig m 1icrias? in blood f W occurred sooncr
with .in inctias:. in iH.:iippiicd teinperat b~After the initid
drop, the n i w l e t:irg eratux gradually .rlcreased, espeoialiy
.C
increase in . i e musale temper.*
at ,45 and 4ó'C 'Cui.,~eciin~l
ture could IY: üttrbui:d tc the hegkinii 4 of retardation af
blood flow ?II the r.ipicle k8eatedat suc,i:high temperatures
as sh( wn ir. liil5. 2. ap weii as ths rise «: $xdy temperature.
Nt:vertheiess. the riiiSle te:r:perature w. :I about 2OC lewcr
than :he teiiiperaturc,,#fheating water i
i
:
die end of 30 min
heiatkg. The tempcr3tire ciunge in the Walker tumor wiis
quite differixt frorn $at in the niuscle d,.ting heating. When
heated with 42 or L 3 ' C wkr, the turn temptranire rose
to abaut O.!;OC be1o.y thc water temper;t$re, and remained
at airnost th? same 1:mpel-atures throi.+out the heating.
When heate'.l at 45 ( r 46"C, the tem.,(rature of tumors
rose, irnrnediitely dr~ip~iecl,
and then sOOii rose again to about
0.S"C below thc water bath temperature. Apparently. there
was a short..;.ired ircrr.rse in the tumor t;lpíid flow within a
few minute!; of her!.$ at 45 and 46'C, jrhich was followed
by a retardation of I/iood !low, as the .levation cif tuanor
temperature iiemora~;~tecl.The absence Of any indications
of drop of u:niperatuit aftur the initial tis in thc tumors
heated at 42 01 431
' :. .s in .igreerrient wi:h h e Observations
by us [38] and 0the.p (451, as previousl) described, that the
:uinoi's remained I Oclwgad at 43'C.
blood flow iri %'&ir
The most úiiportiu.t c;~serv..tion in this , i d y WES that the
temperature of 1-Z g tuinofi 10% signii taiitly higher than
that in die iidj¿cent r t ~isrle temperature ,bring rhe heating.
The above ,muh co 111: be :.ttribiited m; @ l y to the lack of
apprec:iable iirid s w t 41 ed ir.crease in bli mad flow in the tumors (during heating. I1 should be rtresse<:,.howevcr.that the
temperature 'af sniaüq H';ilki:r turiiort dii: not rise ai high 11
thdt Ui the larger 1un.c).s, which may be ai ,tiiiuted to the relatively large Kood 113 u. a i d thus, the resu iririt swift clearance
iif heat.
It
IL
ipp:ii<:ni thd
I
:iii:ii
ti<>,,d
[L:tt
tn :uc:i)rs rid sur.
lEEE TRANSACTIONS O N BIOMEDICAL ENGINLERINC. VOL. BMF-3I. NO. I , J A S C A K Y
1
.
,...
TABLE II
BFR FOR WALKER TUMOR O F RAT 1391
-
.,...
Room ?emu.
Blood ~iou*l .BFR
*..
__
Muscle
Turnon ~ 0 . 9)
7
Tumon (>2.0 8)
-
10.26
48.08
15.66
4.69
1.52
43T
-
Blwd now.
BFR
ZBAS
55.55
14.02
0.49
-
,,95
* mUlOO dmin.
rounding normal tissues is the primary factor which determines whether the temperature .in tumors can be raised
higher than that in the surrounding normal tissues. Table I1
shows that the blood flow ratio (BFR) for the Walker tumors
o f 2-3 g and surrounding normal tissues (blood flow in tumor/
blood flow in normal tissue) is greater than 1.0 at normo.
._..
thermic condition 139). However, the BFR becomes only 0.49
upon heating at 43*C, owing to the remarkable increase in
blood flow in the normal tissues without a concomitant in--crease in the tumor blood flow. Preferential heating of the
tumor could then .be expected to occur in the 2-3 g Walker
'-tumor. A further decrease in B F R and thus preferential heat-. ing of tumors might be expected i f the vessels occlude, and
thus the blood flow declines in the tumors during heating. It
d a s often been observed that the vascular damage in tumors
progresses after heating 191, [40]-[42], [58]. It is conceiv-able, then, that the BFR in certain tumors may be greater than
1.0 during the fust heaíing, but becomes smaller than 1.0 durng the subsequent heating. The BFR for the Walker tumors
lmaller than 0.7 g was greater than 1.0 during heating, which
may account for the relatively low temperature in the small tu' 7 0 1 s during heating. I t would appear that preferential heating
*. f *::mors with matured blood vessels may be difficult because
slit.': ,esselo may react to heat as the nomal tissue vessels do
..mi :he.blood flow increases. It has been proposed recently to
vasodilators to selectively increase the blood flow in normal tissues so !hat tumors can be heated preferentially [59].
Because of the uneven distribution o f blood perfusion in tu31% the temperature distribution in tumors during heating
c.n be expected to be considerably heterogeneous. Recently,
- G u l h o et al [60] reported that the temperature gradients
y-+e larger than 1C
' in locations only a few millimeters in dist ice from each other within the same Walker tumor o f rats,
.~
'' and that the inhomogeneity o f temperature was exaggerated
w
g hyperthermia. The heat damage in the peripheral area
o tumors has been reported to be rather difficult to achieve.
l k relatively good blood perfusion and efficient heat disipation may be incriminated for the failure of hyperthermia to
driage the peripheral area o f tumors.
Jnfortunately, in the treatment of tumors o f internal organs with most of the presently available microwave or RF
hprthermia units, a considerable amount o f heat energy is
de isited in the superficial organs, i.e., skin, and underneath
cumeous tissues. It is then probable that the blood is puued
to -@e heated superficial organs during heating, resulting
- in a
del ne in the blood flow to the internal organs. Therefore,
in ..-e hyperthermic treatment of neoplastic tissues located in
the internal organs, the blood flow in the adjacent normal
r
.
.
.
.."
-
C.
.-
?<
F.
I
-
I-
~
<,
,
tissue of the organs may not increase as niucli 3s that =hiii
would occur by more localized heating of the o i g a n i i i u b .
ever. inasmuch as the blood flow in the neoplastic tirruex t j
internal organs w
i
l
lalso decrease when the bluod is pulled I
the heated outer organs. the ratio of blood now in the tuino,
to that in the adjacent normal t i m e s may still beconic sinalle1
than 1.0 during heating.
OTHERIWLICATIONSOF VASCULARCHANGESm
I
HY PERTHERMU
The preferential damage of tumor vasculature at tern.
perature bearable for normal tissue vasculature and ensuing
changes in microenvironment in the tumors would have pro
found implications for the hyperthermic treatment of tumor%
The intratumor pH is intrinsically lower than that in normal
tissues, due probably to high glycolytic activity in the tumors
and inefficient drainage of acidic metabolites of the glycolysis,
such as lactic acid through the vascular system. We 191 a n d
Others [47], I481 found that the intratumor pH further de.
creases upon heating. Such an increase in acidity, accompanied
by an enduring hypoxic condition [61] and a decrease in nu.
tntional supply as a result of vascular damage, appears to bc
the
cause of additional cell death in the tumors after
hyperthermia Observed by US [Sl] and Marmor and Hahn 1621.
The development of thermotolerance may also be impeded in
the hosüle milieu in the heated tumors 1581.
In the use of hyperthermia in combination with radiation
or drugs, in addition to the interaction o f heat and radiation 01
dNgs at the molecular or ceilular level, the potential implica.
tion Of environmental changes consequent to the vascdpr
changes in normal and neoplastic tirsues should be taken into
account. It is a weil-known fact that hypoxia reduces the response of tissues or ceils to radiation. When heat is applied
prior to radiation, the increase in blood flow, and thus an en.
suing increase in PO, in normal tissues, may enhance the response Of the normal tissues to subsequent irradiation. In contrast, the hypoxic environment in the tumors due to V~~CIIIM
damage [Si] may render the tumor cells resistant to radiation
Suggesting that irradiation should be applied prior to heat
when the heat dose is sufficiently high to cause vascular dam
age in the tumors. The possible increase in drug concentratioi
in normal tissues by virtue of heat-induced blood flow and vas
cular permeability and the possible decrease in drug concentra
tion in neoplastic tissues as a result of reduced blood suppl)
due to heat-induced vascular damage should be investigated
Hyperthermia at relatively low temperatures, e.g.. 39-41'C
however, may increase the blood flow in certain types of tu
mors, and thus may increase the response of tumors to radia
tion. Such an increase in tumor blood flow miy also increav
the dnig concentration in the tumors, making !he combineG
use of drugs and hyperthermia complicated.
ACKNOWLEDGMENT
The authors would like to thank P. Evans for help in the
manuscript preparation.
11, p. M. cow,
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-
I
A n N Lokshinv WLI him in Morciw. U.S.S.R.,
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I
gcry INtiOle.
uur«u.in I’i6Y.
Fmm 1965 to I979 rhc we5 with the Thcnpo
i
i
eRadiology Dcpanmnt. Burdcnko Ncumrur.
g q Institute, where rhc worked on ih ndb
rhenpy cliaicil &IS o í brain tumwa. In 19a1
S k emigind to thc United StMer. knd abc L
-.a“
now with che Dcpinmcnt of Thcrapcutic Rdml.
ogy. Radiation Biology Section. University oí Uinnsroia. Mmneapolii.
Her current rescuch intcrerts
the effect oí radiation and hvwnhnnii
on vascular functions.
..
CE
IIi
I
ck
,
..
1
su
tb
Juow G. R k was born in Seoul. Korea. b
1947. He receivedthc M.S. degrrc in p h y s i o h
fmm th Scaul Naiional Unirorily in 197s inp
the Pb.D. dcgtw in b+ysical ~ i c n c efrom
r
&
Univcrsitv of Minnesota. Minnemolir. in 19%).
m
di1
CCl
tul
ab
<*
F
Minnsroti. where
nar
in i
tumors, human I
1
i
Msrrba P a i l a was born in Minaupoli
wht
lhe
with a minor in niiunl rcicnccr from
rity of Minnerai. Mintmapolis. in I
Shc b u w d c d on various rrs
&e Univuity of MinDsou ria=
cold hvdiaesr riudiu. mil cl
wb
5Kl
lhC
mat.
now
working on vascular hyprthcrmi8 ~ a l y ~ri i b
that bme
~
pian
ir en
H
thai
%yatour H. Lcvln was born in Cltiugo. U. u
1928. He icccived the M.D. d c p e fmm thc
UniversiIy of Colondo. iknver, in 1954.
In 1979 he joined che University o i Minnesota.
Minneapolis, as Pmfc.w>r and Head oi the ikpanmeni of Thvrpeutic Radiology. His pioeipi
arc- of re-b
iotemt include the rok of ndE
iriotiUicnpyiachebctmcntorbrcutcv~cr.id
Hodgkin’s dixrrc. He has lcerured c i l c ~ i ~ ~ l y
on lbnc.lidother topics in radiation w d q y in
major cities fhtwghout thc United .Que< iad
Europ.
Dr.Lcvifl is th+ Past Prcridcnt of the Amcricin Sorirty ofnicry>cutic
Radiologists and he ir the cumnt President of the Radium Society of
America.
con(
1’
tirsu:
bctw
ciihe
-3
1
-
lirrUl
inter:
31
2 ii i
1 Is SI
Ma
tn m
XStiOi
Th
l’”W,
hcnr
i
Fig.
1. Basic antenna design. Schematic of thaintcrstitul microwave antcnna used m these experiments The antenna fits
into I blunt-ended nylon catheter
TABLE I
left
right
I.7m
2.8Cni
1.21.Ocn
0.50.5rn
0.1-
O.7m
111
O.HCrn
1.20
1.X"
0 . 9 ~ ~
0.5m
0.3tn
0.4-
44.l.C
0.9tm
0.3ci
0.3m
16.1.C
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r
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Fig.
2. Bi
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IC"MI.
pom'cr d
optic tern]
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brdin.
Recent
lhernionie
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Lb.9
I
.*
,
~
~.
,
.~
-
Bureau of Stantiardsi iiicriiir, therriloiwter over the tempcrature range 3O*Sl0C (+(J.i)?'C aLriiracvj. Both the mercury
1hermometi:r a n d tt:riperiiiiire probe, were iriirticrad in .I
tariable temperatu!c . < i r a l a : irig \r i t ' r bath I1li:nnorniu
#. 420) for calibr~tr.' 1 1 ~ r o c e d i i r ~ sT. m m r a t u r e \:orrectionr
wcre made ror each he 1 s iridicxtc.1 lq caiibratiiiii data.
. . .. .
Stereota.njc m a r i i p t i l a i m weIe u r d for catheter insertion.
p$obes .vi>:: rigidly held I>)stereor&yic &ctrotl*
he 19 cqxrinieiits iisiiig <.ne antenna. tlie nylon
. . .. - .
.____ 4atheter (Best Ind.) m'~
guided into tlie posterior occipita!
].....--.ny~rb h e and advaiiced pxrdlsl 11) ihc c o r t e a l surfice at a deptli
nging from 0;4 to I 3 cni. rherind Astribuiions wen: niapintern I!S .il(~iigthe entire length crf the inserted
Lqnper.~it'ir:probe was advanced 3f each location
l..-*;:Zi-= h I mm increments perpenriicu~arto tile ionpirudin:ii axis of
. ....
~.
..._~~
~
.--+,z
~
~~~
.
.
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, f ..
. A
'.
In contrast, in t:
,,
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h
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hnor
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torprut
b e p',
Each te
,,
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11
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.
experiinents iising an array o f t w o o r
as, the riylon catheters viere inurted into the
arietal lobe orihogc:id t u the s u r f a a <of the brain. In exyeri.
+ants utilizing tNo irlicrwave antennas, the catheters 'were
ipserted parallul tu .lie sagitral Sirius and were separated by
I : ~ ~ ~ ~ ~ ~ i < 1.0
' ~cm.
~ In
~ nine
r p expc,rinierts.
. ~ ~ ~ I an
B array
~ . o f four antennas was
:quare wnfigiiratiun with an antenna at each
, :. I ' ' LI t i l ~ i i t tends wtiich domer. The dhgoni.1 rcprdiion of ioippoing antennas W I S
: '.
I: :.hi[ 2 tliwiigli the 1.5 cm and the si'je ierigth of separztjim was ;ippruxUii;lteiy
1.,1cm. In enperin:~nts iisirig multiple anterinas. the YSI
1
<
I , i i i i p iitrcontiolled
dherniistor probes w l e inserted into the posterior occipit.ii
1; !
I I b . ' :..IO l'ur iniiltilolx and advanced awimicirly, perpendicular tcl the axis of'the
I .! I $ I ISP iherrni:i.
antennas. Thermal h l d h r w < : carefully mappad in 211 experi.
I
I k.
I
' : Lh r:mpxahmts by mdklng
[ipI<: parses ;st .;.iryjng deprhs in the
I 'r ni, trcJi,iwn:.
h i n . Teii>peraturr ~ , , ~ r c i n e nuirt:
~ < , taken a t I : ~ > i r iii:r,:.
i
, ' 1 ',h t ! * ~ : . i ~ .11
, n ~ m i s diiiriili r,s.ii p ,>, I.: .I?C:J:LJI:
,:.itrthui,iir,: ".<,e JIS,
~
,
~
e
5e.o
O
0
va
Y O
O
I
5.0
3.6
4.0
OIüTANCE Ismi
I
o
<.O
P.0
2.6
6.0
4.6
c
I
vu <
ThwnIalol 1i.m
h
3.0
5.6
4.0
CHBTANCE Irni
6.0
4.6
This f í u n shorn the temperaturn dinributions (upper graph) nmrded from Uuec YSI probes in a pass thmugh
the bnm papcndicuhi to the longtudinal uir of the antCMIs. T h e onentitions of the thermistor probcs and the four
micr?wave antennas are depicted in the lowu graph. The tract ofthc middk tempmhlrr pmbc (YSI 2-roüd <r*ngIes)
WU pund on the cortial edge of aniennas Ai and A2. Anothu temperatun probe
I-oprn quaies) was poutioned d o r r t to nntenna A4. The third probe (YSI 3-0pen cucles) was inserted through the medial third of the fourantenna m y . The distance between the thermistor probu Was 0.4 cm. A sin@e fibu optic (LI-solid circle) probe was
passed in a pLne pimilei to the antennas in the center of the array. The x-axis scale is the same for both p r a p k and i s
bued on exact Itcteotaxic coordinater.The y-axis in the Iowa graph is a rclitive scale of distance.
Fa 5.
(Ya
."
...
.
.
...
.".
..,,.
..~
."
.I
I
, I
,.-
,I
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. ."
....
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.
I."
60
ANfEOIM )
f
f-
POSTERIOR
Fi.7. Irotheims generated by a four-antenna m a y m the right hemisphcrt of a developing dog with I histol~icallyconfumed @oarcoma Temperatures wm mcesurcd in bofh horizontal (huh marks) and ve-1
(crmes) pbncs to the
four-antenns array. Three horizontat p h n a are shown at depths of 1.2 cm, 1.0 cm, and 0.7 m The antennr phament
was similar to the piacemen: represented in Fig. 6 (h, = I .O cm,hB = O 5 em). Maximum NFP was 20 W.
Fir. 8. This low power *w (30x1 üiurtratcs the orientation ofa YSI
:humistor piobe tract (large solid arrows) to an antcnns (Al) in a
horizontilly a t section. The uact ofthe Luxtron ñber optic probe
(L1)was &o urüy idcntüied in this fku.
ferent antenna design (131. However, the temperature distributions were not symmetrical around the antennas, as
predicted by the theoretical calculations which assumed
uniform blood flow in the brain. The lesion invariably extended
farther mediaily into the white matter tissue compared to the
lateral extent of damage into the cortex. Two factors could
account for this observation: 1) brain tissue perfusion is
normally lower in the deep white matter compared to gray
matter, and 2) heat dissipation is greatest near the cortical
surface o f the exposed brain. An additional factor o f potential
importance m accounting for asymmetrical temperature
distributions in the brain is the difference in dielectric propc
ties of gray and white matter. Due to lesser water conten
white matter has a lower permittivity and higher conductivit
and hence, a higher specific absorption rate of microwi
radiation at 915 MHz than gray matter [ 141.
The thermal dosimetry data measured during interstiti
microwave heating of normal dog brain reflect the variabilli
of brain tissue. The inüuence of cortical sulci, ventricles co
taining cncbrospind fluid, and large venous sinuses. in ad<
tion to the variable cytoarchitecture in gray and white matte
result in complex t h e d distributions. Temperature maxin
were not necessarily found in the center of the four-antmi
array. The maximum temperatures at a depth equal to h
(brain surface to junction) were most commonly observed
or near an antenna nt the edge of the square array. One pro
lem with using interstitiil antennas in the dog brain was th
surface heating to damaging temperature levels was MI
m d y observed. This could be due to absorption of excess¡
energy at the tissue-air interface. However, it should be notc
that these antennas were specifically designed for herüi
larger regions o f tissue at greater depths than can be atiemptc
in the dog brain [l3], [ I S ] . An important advantage of usil
multiple antennas was that less power was required by e a
antenna to generate therapeutic temperatures in large r a o i
of tissue. This was in part due to the additive effects of il
overlapping electrical fields. Hence, the amount of eneri
deposited around the insertion o f the antenna and cathei
into the brain was reduced and caused less tiswe daniage
the point o f insertion compared to experiments using a sing
antenna.
The problems associated with thermometry meesuremen
in electromagnetic fields have been previously reported 116
,u
r
19hd
.
,
c v o C~I ~~l . L: 0 C h L I Z I : I )
...
i1Yi~ERTIIFR!dlA A N D BR.AIN TUMORS
61
.
micrographs ale 48üx.
The problem o f heating of the temperature probes b y
r heating, the thermistor. probes were oriented at right
O
I
the microwave antennas. Temperature recordings
fhe histdogic.tl rerultr oi t h w c\pcrinitiits are iiiipurriiit
rerpeit;. L , , r !p!~:,,I,+.A
C v i d c n c e d r thermal h r n +
threshold in the normal dog brain using microwave heating for
60 min occurs between 42.0 and 4 2 2 ° C . Second, these temperature threshold values for damage are similar t o those
reported by our group using ultrasound heating in the normal
cat brain [ 181. It should be noted that the difference in
normal body temperatures between dogs (38.3'C) and humans
(37.OoC) may affect the thermal thresholds for damage in
of these parameters in vivo needs further study.
The results o f locally heating brain tumors in an experimental glioma model with the MAAH system show the biological feasibility of using this system to heat human brain
tumors. The potential limitation of the present interstitial
r n i c r i v s c heating system is die in3bil;ty to prtsisely tun.
treatment potocoia (up to wven day
protocol haa been app
seated tumors 1201. The ult of
with prbnuy central nervous
been reported [2i].
hhuy results from Ph
therapy and interstitial
centmi nervous system [
colkrysr lowed that ptiepts
momdiothcnpy had an owrail r
with a 71 percent e
thb study showed that elinid
tQ using intentitid heating 00
frequency and microwave ippiicators.
niir
ACKNOWLEDCMEP~I
The authon wish to thank Dr. D.DI Bignu for g QO sly
iuppiyiq the purifid SR-R$V, E. Jkfich and E.% x m i o i
iechniul udrtuice, E. Mñlemiui fo hirtolrqjcd prep
tion, P. Richey for graphic design, and P. Home foi
mkrorcopy.
111
I21
I31
I41
INTRODL.C.Iicjv
~
ALIGNANT brain tumors caiirwi. ;,re.:arly be erkctiveiy
managed with convent1on;il t!~er:::ie~rtic moc$liries.
orary clinical manageniw; w t i s i , 1 s c'f a szqbentiai
of surgery. ionizing radi4tio.1, iiid :hdmoil erapy .
ommon hrain t.un:or id a ~ . i l d i ~die
. d i l b 1 stoiii.i
I, has an irvariably i a t d tim: c w r e , rrriiy dstiii:
n two years despite t h t ros: asresrivc $ i n i d
id on this fact alone. ,the ir
nt o f intracraiiial hypertlici-rhia Jrc xcll j~ustihd.
rthennia as an experuiimta! t; :atmeill for' braiii
s based on a sound bioph, skd rat:x& [ I ] . F$rther.
development of intracrat$id 11) iiwtherma, yhilr
e 1iioenginei:ring prohleiri. may r q i s e i i t mie ! o f the
amples of hyperthennal tre1tr::ent o!' d?episeated
on. The brain, :situated within i!ie cranial vault. is a .
t
terfaces) cannot be preciszl)m d e r i n d , 3
uver mort: than a p p r o p a t e l v 10 c m fr+m an
face, While t h e b % @ s u11 re:vesents an i pedi.
vasive Iiyperthermal't~ieri,p!, this sdid, $able.
ribed platform offers c c m ~ l i r a b l e advdntages
techniques are utilized.
rthennal techniquey ap;ili,.~bIe to úitratranial
I received Lbrch 25. 1983; W v i s d
heating !the ftlirc wain v ill: ironinvamp iilti~ioaicdevices.
lliing eJectroi-iri:ne+
teci n i q i c i , Silbeigian rlr al [41 have
remrted heating tlii1rabbii h r x i with .I t<mirii.asive nignetic
iii.iuctah device. Sipiaras ?t d [SI rep x t e d Iitatinp the cat
brlin w r h aii iniasivt micr i w ~ i .device.
'
i n dl cases. regardless
3f whether iniai:va o r not::o\as.ve heatin8 was utilizsd, üssue
temperalures were 4 a s u l r J by masive :&hniqws.
CliniOal attempts !ut in1 :acranial hypqtherniih (for expenniental $rain tiirxi; $erap:. j h a w beenrerbrted by Heimburger
?r al. [tlJ using a i *$terni u!trdsound w$tmand 1)) Samaras
?tal. [ S I , [?] u<:iig $11 imp:anicd microivjve antennasystem.
In oqder i o rstio+üy administer intratrmial Iiypeitiiermia
f ' x brain tumor thet;ipy, :here are foil:. basic problems that
niust beisolvcd. I'liey are
1) heat dclivmy
2) temperature ni(asurc::ierit
3) telnperatuie cqitrol
4) pretreatmest dtrd p'st:rcacment cstunation of spatial
thennal fieid distribyiions.
In Gis paper. specific alutions for the first thrce items
will be ,derribcd; $e lasi (alii! most difficult) iteni will be
dixusseii. ri:cognizi&g th.it no practical solution presently
:xists.
I
Parted in tiart b y the Amerbcan Cri
PDT-LOS. in part by the h'NCDS
11,. and in p:tn by the Whit&
Fa
from tho Dean. Schi,irflof \fe
mtogy. ;mi
tho ~ i v i s i o of
n N:ui
author is with the Neurooniulogy RCY. ,LIC., :Labomto es,
mmenl
Of Radiation Onwloyy. Cnivcriit,i , :' hlaryland S$oril
" ~ ~ ~ + ~ ~ i i m $10
o wz .i 2 i l I .
De
o;
i
I
+
i b
,
.,
! ' .
Ii
1 "
HEAr DEUVERY
F u n h e l i t d l to Wery tivperrhermal t b r a p y i8 the problem
of deliFring heat k1 thi: target tumor, while sparing the
riinoun/ling noiinai Tissue. Ulriascknd. m n p a r e d to electronuignetil radiatnin, Las superWi: penctratbn depth iii aiolopical tissues. and #itq the ;ippropriate insrhimmtnitiuii, precise
focusin# at (depth rnhy b e Jbtainad 121, 131. Howeyer, ultnwinic intracranial hyperthwmia is not ncihinvasiw; since ultrasound dbes not iien@irate the skull weii $ section of the skull
niust b( surgically iemoved h r each idírasonic traniducer
eniploybd iri the trea#ment. Furrhermore, p the contemporary
absence'of noninwsee thermonieiry, "nohinvasire" ultrasonic
heating ' still reqiiirh inviisive tissue ii)nperaaire measurenic:nts.
Silbetman et 01. [4] :ire irivestigatitlg the feasibility of
using magnetic loci)) indimion for norrinvasive intracranial
hyperthermia. While this b.mt delivery tcahniqua is t ~ l non.
y
invasive, it still rcqidres úivüsiw tissue temperature measurenient. burthennarc, unlike ultrasound. i t suffers from a
crucial habiiity t o &cur the hcat-produdng energy (in order
to spare normal ti$e). and relies soMy on the hope that
differential heat tr&sfer between turncmr and nomial. nonrepairin$ n e v o c s tissue will result in preferentiíii tumor
heating.
The consirairits on an; h p i a n h b l c Intracwiiil I i a i d s -
~
I !
'1.
4
1
!I
~
j
1.
'
~
,
'
'
aver> device include rnininial size t u miucr brain tisue
damage upon implantation. maximal rigidity io increase the
accuracy of positioning. eiicapsulation i n ni~iitoxic, nonreactive material. a reliable spatial energy deposition patiern.
and a simple means of altering spatioleniporal heat delivery.
O f all the modern methods of inducing controlled hyper.
thermia, electromagnetic radiation in the microwave spectrum
appears to be the most appropriate for invasive intracranial
heating. We have previously reported the results of in vivo
dielectrometry in felines [SI. Measurements of the conductivity (mS/cm) and the relative permittivity (unitless) of both
gray and white matter in the brain were measured;in the range
of 0.5-1 .O GHz, the uncertainty in the measurements was on
the order of 1.5 percent. Figs. 1 and 2 show the frequency
dependence of the conductivity and relative permittivity of
feline gray and white matter over the range of 300-1000
MHz: values at 1 1 0 0 and 2450 MHz were not measured.
but were estimated by extrapolation. These Same figures
also show an estimate of the depth of penetration (O) (dis.
tance to reach about 63 percent attenuation) using a simplified approximation 191, [IO] of the form
IS
M
I,
I5
I.
1
.3 4 5 51119l.O 1.1
where
w radial frequency (rad/s)
c speed of light in vacuum (3 X 10'' cm/s)
relative permittivity (unitless)
a conductivity (mS/cm)
E, free space permittivity (8.84 X lo-" mF/cm).
The results of this calculation serve as a useful index in the
design and selection of implantable microwave antennas.
Antennas for invasive heating of the brain have been
reported by Strohbehn er d. [ill and Taylor 1121, and are
of a monopole (sleeve) design constructed from m a l l , semi.
rigid coaxial cable. We have studied the heatinn Datterns of
this monopole design in both static phantom, live, and freshly
exsanguinated feline brain. The antennas can be constructed
from semi-rigid coaxial cable with an outer diameter of ap
proximately 0.7 mm, which satisfies the requirement of minimal diameter so as to minimize tissue damage upon implantalion. However, this design is not very rigid and tends t o bend
" -6
and buckle upon insertion.
-.
i n an attempt to improve the rigidity of this device, we
heuristically developed a new design-the c0-l
slot rad&or
r
(shown in Fig. 3). The coaxial slot is f i e d with a high thermal
conductivity, low electrical conductivity adhesive [I31 io
preserve structural integrity. The energy deposition patterns
of various design lengths (d = 10.8, 14.4.21.1.and43.7 mm.
respectively, where d is the distance from the tip o f the an-1enna l o the center of the slot) were empirically studied in
static phantoms [I41 encased in a thick wail styrofoam conT a i n e r , sealed with cellophane and warmed in an oven to 35°C.
Each candidate antenna was operated at 2 4 5 0 MHz with the
u
same net power: equal color contours (corresponding to
-
_-
Fig. 1. The frequency dtpcndenEs of conductivity (mSlcm) mht
permittivity, and CaiNlated pcneíration depíh (cm) for feline 0
matter over the frcqumw nnge from 0.3 to 2.45 GHz.Conductiv
and permittivity at 11M) and 2450 MHz wme estimated by exkq
lation. o* * conductivity, eg = relative permittivity. and Dg dog
ofpenetntion.
Fg. 2. The úeqwncy dependma of conduqlivity (mS/cm). reht
Pe~iitivity,and cilnibtcd pmetralion dupth (an)for feline wh
manor over the üequcncy nryrfiom 0.3 l o 2.45 CHr Conóucti*
at 11W and 2450 MH2 were estimated by extrapolation. vu N
ductivity, ew = relative perminmCy,D, depth ofpcnctntkn
-
.-
I-
-
-
Te wsu
-.
@Co-cC
-
L
2.45
A* h . o / q ; N*4,6.8
>Lo= 12.25crn
. ..
T.lb"(
E. 2 I
cimrit
C."IC<*"
3. A schematic d L g n m of the ndbting portion of a c o u n l !
antenna The design warempirioinu detcnmcd. The lenpthd
to in the text is the dhtence üom the centcr oi the dot to
short-circuited end af the antenna. For operation at 2450 M
Fig.
ho = 12,25
A functionalantcnru
the coaxial dot compkl
r i d with a high thermal conductivity, low olwcttiu~conduce!
material 1W*andis encaPaiMed
thinTeflon sheath to PI-
conlact between the copper outer conductor and b n i n t i ~ u e .
approximately 38'C) obtained from a liquid sheet piar
over the "split" phantom surface immediately followin¿
20 s heating yielded the patterns shown in Fig. 4 . We seleci
the pattern obtained with d = 10.8 mm (which conespor
to an eighth wavelength in Teflon at 2 4 5 0 MHz). as oppoi
1
F
:tie ideiiticd anattvii. al locatitin of t h . k I i ~ i ?:',Ir:
br ii!:.E:..arriinaticin <if the t<vu patterns shows an i - c r t : ~ : J
ra.lid heitiiig gatteni for tb? dot design comp(re,t -o í t e
sltr\c deign. T i e a x d heatid;: 1:atterns appear to b
cornprat~le. Therefore, the rr~xial slot radiator ilt:.;ipn k ca'Jse Jf it$ mi&nal radial sit-, improvzd mechadca: ri:idii: ,
and unp.oved heating patttjii.. appears appropiat,! ti): :.titrasraiiiai heat ilelivery. In p r k r to m a t this device witti a
nontoxic materel, either a q f i m spray or a thin:w;il Teilon
tube [16] can b e usad to qicapsulate the coax+J hi..
Oiir
experience withthe device is that, io the absence of ioniwti\e
t c j i ; n i ii
influences, the $palia1 heati@ pattern is relatively reprodurib k , although variations, probably due to mechanical L b r i c i tkin technique,
occur.
A single antpnna may be useful for heating residual tumor
once the bulk of the tlll11or has been surgically removed lo
decompress thetbrain. However, in order to heat brger tumor
volumes, a sinde antenna operating at 2450 MHz i s totally
inadequate. Foe a "no blooQ flow" case, the devlce 1ieat.s an
appro,xiniately &ylindrid vdunie (to temperatures exceeding
4 1 O C ) of radial gimensioa 0.6 cin and axial dimencion 2.2 cni;
ir^ the case o f @e sleeve design, the radial dimensbn is on the
order o f 0.35 c k . Therefore; at best, the slot des$n operatirig
at 2450 MHz can only heat a 2.5 cm3 volume to ttmperarures
above 4i°C, whereas the sl(eve design would o d y hear approximately I cm3.
There are IWD
possible approaches to increasing the volume
of heat tissue; one approach ir to increase the number of
ariteniias, and the other is io change the frequenay o f microwave radiation. Fig. 7 showsjthe frequency depenuence of the
axial dimensioq (2d) of thd dot design and tht frequency
dependence o f ithe effective penetration depth (Deff). The
effective penetrition depth i s
60
Deff = o.8 [ogt*y]
+ 0.2 &hit.]
where the assurpptionr are btirig made that 80 p s c e n t of the
brain p a r e n c h h a is gray matter and 20 percqnt is white
matter, and thbt, furthermore. this weighted average is a
reasonable estirbate o f the material properties thlt the iadiation üluminatesJ
At 2450 MYz, D e f f = 13 cm and M = 2.2 cm; at 300
MHz, Deff = 30 cm and 2d':= 17.7 cm. It shoul~be noticed
Deff/2and 2d correspond tb the radial
that at 2450 "2,
and axial dime$sionr of the, cylindrical volume k a t e d above
41OC (when the integrrl fhcrmistor temperature is maintained at 45'). and one c w l d , by linear frequency scaling.
estimate the anllogous volwhe zit lower fnquencks. It is also
noteworthy that axial dimen$iorr greater than 10 em are prob.
ably not useful b the human brain.
TEMPERATUREMEASUREMENT
Tissue temptrature measurement during eleairomagnetic
heating requireb the use of special themomewy systems.
Temperature mtanurement ih high intensity microwave fields
can be accomplished with sniall. nonmetallic (anü thus ininirnaily perturbing) sensors su<lh a s the fluorooptic probe [ 181
ilimiiistors. except for the B ~ i ~ r n
p p~e n[ i')I arid tiicrmis.
.
.,
66
I¡ 1.1 KKAUAI
r i o v o x rn1.>\!1
nIcAiL ~ . X G I ~ ~ I . U I V\ G( 8 1 .
n l i t 3 1 ,YO. I , J A N I : A H ~
Ip,
, ,.,!Al:
‘C
...
..
.....
..”.
I
.
. -...
..
..
..
.. ..............
. ......................
.*.*..................
............
............=.........
......-.....
...
.u1
Fi. 5. The quniiequüiinum tempemtun distribution oi
the
iIS
wavelength dot antenna d e n i m p h t d m a kctimmwnack
thaired feüne brain. The antenna was o p c n t d at 2450 M k with
a control system thit mainbind the intern thmninor at 4S +/0.1’C. Temperatures were meuuiad with a mlibrsted Luxtron
lOWA thmnometer and I miuomanipuhtor. The figure depicts
tempemture measuuIcmenb made dong the i n t a m axis ai v ~ o u s
rsdisl distances (0.3,O.S,0.7S.i.O, and 1.2s an).
-”
..
,~.
L
.
....
..........
....
.........a
......
-.
..........
P
-_
I
I
_
I-
.
-.
n m was u d .
Step I: I f lei(
-
.~
> 0 5 . then Al
= K1 + K4;else KI =
coordinates of the tuniiir margin is k i w u n . ilic íi>llo~<i
questions must be answered.
K 4 = K4 + K 7 .
I ) What tissue (malignant and nornial) irniperal
Step 2: I f I q I > I .O, disable the inteser controller by be prescribed for treatment of ihis patient?
by settinp oi = O and proceed to Step 4. If Ici I < 0.5.proceed
2) What duration o f time shuuld the tissues be exposed
to Step 4.
these prescribed temperatures (using the siiriplifying PSS
Step 3: I f lai I > 161- I I, then K3 = K3 - K6; else K 3 = tion that a constant spatial temperature distributi
K3 + K6 and if luil > lot-I l. then K6 = K6 - K9; else out the treatment will be used, and noi con
K6==K6 + K9.
required fractionation schenies)?
Step 4: I f I q I > 3.0 or I q 1 < 0.6, disable the derivative
3) Which array of implanted antennas will most cl
controller by setting 61 = O and proceed lo Step 6.
approximate the prescribed spatial heating paitern
S t e p 5 : I f 16,1>16,_,1,lhenK2=K2+K5:elseX2= implies selection of the length or frequency o f opere
K 2 K 5 and if lo, ¡ > O , then K S = K5 K8; else KS = K5
each antenna and the anatomical location of each anten
K8.
At the present time. our knowledge of the medical p
Step 6: If any K-value is now less than unity, then r e s t tion (temperature and time) to achieve biological cffec
that K-value to unity.
is, at best, vague. However, in order to minimize
Step 7:Calculate the generator control value (CJ and tissue damage, it is essential to maintain the temp
begin a new measurement/control cycle.
outside the tumor volume below 42'C. Furthermore,
i n our implementation, the values o f K7,K8, and K9 are tumor temperatures should be above 42'C, normal t
normally unity. We have found that the initial values o f Ki, temperature far from the heated site will be about 2loC
K2, and K3 primarily affect the time required to reach the heat transfer in tissue does not permit spatially sharp tem
target temperature; this effect becomes more pronounced ture transitions; uniform tumor heating is not practica
as the time for a measurement/control cycle is increased. (considering the heterogeneity of the tumor structure)
The generator control value (G) is a digital word bounded probably even desirable.
by the bit length of the computer being utilized, and further
In order to select the most appropriate aria
bounded by the bit length o f the digital-to-analog converter it is necessary to be able to predict their re
being employed to drive the generator. i n our application, a 10 pattern, which requires knowledge o f their ener
bit converter is used and, furthermore, the analog generator pattern, the effect o f tissue thermal conductivity, a
transfer function (input voltage to output power) is h@ly
effect of tissue thermal convection (i.e., knowledge
nonlinear. We have found that this control algorithm does not three-dimensional blood now vector at any point). S t
require a linear correspondence between G and output power, et 01. 121 J haveattempted to mathematically simulate
but heuristically seeks the value of G necessary to achieve the n o d brain.. Probably the greatest difficulty in
a stable tissue temperature. However, it is necessary to adjust the resulting heating pattern is the absence of d
the maximum possible value o f G so that it roughly corre- edge of the direction and magnitude of blood flow a1
sponds to the generator input voltage yielding the maximum location in and around the tumor. In our laboratory, w
power output. Furthermore, it is pNdent to provide a maxi- systematically attempting to empirically determine the sp
mum output power limit that will not damage the particular heating patterns for various array confiurations in normal
antennas being used.
tumor-bearing canine brains. The objective is
For applications utilizing multiple antennas with multiple database which may then be employed to ascer
sensors and either multiple microwave amplifiers (or a singie tivity of the various simplifying assumptions used m
generator with a time multipfexing scheme), a single sub- theoretical formulations of Strohbehn er al. (211. Fur
routine realizing this algorithm may be employed with an NX more. localized blood flow estimation (using thernlal clearance
.~
22 input/ourput matrix containing the parameters for each of and brain blood flow manipulation using hyper/hypocap&
the N "channels." Because of the adaptive nature of the is expected to elucidate the level o f influence of blood flow
algorithm, compensation for mteractions between ChaMelS on spatial themal distributions.
will occur; however, the degree o f compensation is directly
-". related to data processing speed (throughput lime), so that
CONCLUSIONS
.. a slow machine wiu result in poor compensation.
Intracranial hyperthermia can be accomplished by invasive
and noninvasive means; tissue temperature nieasurcn~entscan,
at present, only be accomplished by invasive techniques.
Practkal solutions for three of the four problems under- This paper has presented practical wiuti»ns to some of the
*-. lying administration o f intracranial microwave hyperthermia problems of accomplishing invasive intracranial microwave
have b u n described. The fourth and final problem involves hyperthermia. In order to proceed witii the development
--'
the pre- and post-treatment estimation Of spatial thermal of this approadi, it is essential ilia; we gain an entpiricnl
field distributions in the tumor and mounding normal and/or theorctical understanding of hon iniracranial heal
tissue. This is the problem of thermal treatment planning transfer processes operate.
and dosimetric quality assurance. In other words, given an
individual patient whose tumor has been radiographically
R~RENCES
localized so that a reasonable estimate of the stereotaxic
K1 -
..-
1_-
_..
--
K 4 and if 18il
> I&¡-,I. then K4 = K4 - K Y ; else
-
+
I.
,!
- .
.
,
?'!
, ,
, -.,o\ lilO\I~OICAL ENGINEERING, VOL
!/
BME-33. NO 5. MAY 1986
411
i ~i $ 2ti fication
~
of Thermal Model for Human Tissue
MORTEN KNUDSE.N
AND
. ..\ .itai>le m o d d xtrueture ufspntbl and temporal tempr-
'
iirsuc, exposed to electromagnetic heating
~ t s r t ; ,,,' I, d i n g , is drrrlopd. This model. denoted the control
. , ; I ~ r 11
t ~
for tlirrmiil dariniriry In hyperthermia cancer therSI,, i
OW>: ,-t:ci~l
riintrol model parameter v i h e s for various types
I I...tnt!,:.
r i e i . i i L~ISUP arc determined from apriori knowledge about
l ' l l r l po\tuon and puniniewrs. The control model parameters for
, :,\\LO,
u t ,!stiinnted froin patient treatment dntn through the use
ifirsrion technique. The resulis indicate that the conitre is adequate. With the available #priori k w w k d g e
detirmiiwd control modd parameter values do not
I .II,:I
r:t,roduí,i the rrprimentnlly ntinuied values. Accord.tn C I C I I¡fie
, ation bawd anexperimental data is recommended, if
1-1
I.
~ I U J, , N I
in human
I. INTRODUCTION
I 1 it.'::hl \ I , models o f human tissue play an important
p . 1 ~:n .!ypcnherniia cancer therapy, in particular for
~ m . ~ p i,i.i:c:d
it
simulations of hyperthermic treatments [I].:
í r r thl> .hn aiid Roemer [ I ] have divided the field of
I , ' I I I , I ~ ,iwnietry into four areas: comparative (evalua-
T .
rent heating modalities); prospective (individt:r( treatment planning); concurrent (feedback
.
I . ! rljl :!urmj; a treatment); and retrospective (post-treatI
' 1 c! ilti (tion o f the therapy). The ultimate goal of pro[', , ' i i . c incurrent. and retrospective dosimetry is to
t cwitrol, and estimate the complete temperdture
i,,, I i n ::if: iuinor and its environment. This requires very
; 1 h ! '. rrtldels containing detailed and accurate iiifor11.' i i v i h i : t patient inatomy. electromagnetic and therI:
: i h iie iiaranieters. and physiological response. The
' : ; ~ I ~ I ! , :d iwdel building approach is mainly theoretical
t'
'; / i r I:. ' t h.xe mathematical models are developed from
11)
la i s and relationships.
is however. also a need for a different type of
I!'
: ~ . l vhii li has a simpler structure and does not require
i i ~:
~
s : i n i i .ition prograiiis. To predict and control the
( ' ' ~ I I L V ~ I ~i ~
n , a. few selected locations in the tissue the
:I
LII infi'rrnation is: which heating and cooling input
.ire +red
to obtain desired steady state temperI : ' , ! . : > iii th: specified locations. and how fast can the tem)i ~ . : i u r . ' ~
hci changed? To contain this information, a low
w:I t Jn$'?r function is most appropriate. The model is
1'. ,111 or :ornp;irative. prospective, and concurrent do>:~:~'irj.
bi I ;IS the immediate application is for design of
,
I
I..
:!Ef
ipili
'8
~
8,.
I
I
in. Ivns.
:rq~' PCCIWLI March 7. i9n5: September
K ~ L L I V I, with the Inslilulc of Elcctn>nic Systems. Aalborg Uni-
I /U
,
Ikpanineni of Oncuiogy and Radioihcrdpy.
.'(I
-tc -1 ('. 'ir Kcw.1n6. R.diurmrsrionen. Airhur. Dcnrnsrk.
1 , It ILIC '.uiiihi.i X < i O ' I * l l
'
JENS OVERGAARD
feedback control algorithms, we shall denote it the control model.
Experimental modeling-the alternative to theoretical
modeling-is very suitable in building the control model.
Experimental modeling o r system identification contains
two steps: first, the structure of the model must be chosen,
and then the model parameters are estimated from measured input-output data. As theoretical and experimental
modeling are complementary to one another, both methods shall. however, be utilized.
'The purpose of this study is
-to develop and verify an expedient structure for the
control model;
-to determine theoretical values of the control model
parameters for different types of homogeneous tissue;
-to estimate control model parameter values from
treatment data for various patients and tumor locations;
and
-to determine i f the control model parameters can be
calculated a priori from known anatomy and tissue parameters with sufficient accuracy, or i f they must be determined experimentally in each case.
In the following, the applied hyperthermia system is
firsf described. A theoretical tissue model based on the
one-dimensional bioheat transfer equation is developed,
and the computer simulation program and the chosen control model structure are presented. Next, the prediction
error identification method is adapted to the current problem, and the method is applied, first to input-output data
from the simulation model and then to data from 24 clinical treatments. Finally, the model structure and the calculated and estimated model parameter values are evaluated and compared in regard to accuracy and usefulness.
11. THEHYPERTHERMIA
SYSTEM
In the hyperthermia system used for the patient treatments (Fig. I ) , power is applied to the tissue through an
inductive applicator, and surface cooling is provided with
a plastic bag with recirculating distilled water. The system is further described in 141. The effect of heating and
cooling will decrease with. distance from the tissue surface. and the combined effect can cause a temperiture
maximum in a fairly superficial point (maximum depth 23 cm; see Fig. 2).
The tumor is assumed to be located between +I and x2.
By manual adjustments of heating power and cooling
water temperature. two temperdtures. e.g.. T(.rl) and
TLr?), can be controllcd.
I n a new version of the system. a microcomputer per-
,
T' = 7' - Thi h the increase in temperature in relation
to hlood trniperaiure
y IW/(m . "C)]is thermal conductivity of tissue
p,
c,
and ph Ikg/m'] arc densities of tissues and hlood
and q, [W . s/(kg . "C)]are specific heats of tissue
and blood
m [m'/(s
kg)] is flow rate of blood per unit mass of
tissue
S(x) [W/m2) is the absorbed power density.
The gain as defined in [SI is
.
COOLING
Fig I.Block diagram (
i
one-channel
f
hypenhenntii ryricm
where
X
Distenc. lrom surfor.
Coolins ~ H W I
Fig. 2. Temperature distribution in tissue along an axis through the middle
of the applicator.
P = Al, [W] is the absorbed EM-power
A [m2] is the applicator area
1, [Wlm'] is the average transmitted EM-power at the
surface per unit area.
where
For a plane wave C(x) = ( I / A L )
L [m] is the depth where the plane wave power is reduced by a factor e.
Simulations and measurements on phantom material 141
show, however, that although the decay is close to exponential, the plane wave approximation is unacceptable.
instead an empirical expression is used
Fig. 3 . Cantml plant. io is transmitted EM-power. T. is cooling water lcmperature. T l x , ) and T(x,) are tissue kmperatures in depths x, and x2.
(3)
where the constant B and the actual penetration depth Lh
forms feedback control of two tissue temperatures 161, are determined from phantom measurements.
The surface cooling gives a boundary condition
[12]. To design the controller, a reliable model of the
thermal process is required (see Fig. 3).
Ill. MODELS
A. Theoretical Model
Modeling of the process (see Fig. 3) consists of two
steps: calculation of the local power density from the ap-
plicator, and calculation of the temperature distribution in
the tissue as a result of the generated power.
The bioheat transfer equation is a widely used mathematical basis for thermal tissue models. Although it is
known to have several limitations, it has proven to be quite
useful for obtaining the major features of the temperature
distribution in relatively large regions of the body [13].
As the power density variation around an axis through the
middle of the applicator is small in directions perpendicular to this axis [4], a one-dimensional approximation is
considered reasonable. The results of this study can give
some further evidence of the validity of the applied assumptions and approximations.
For a semi-infinite homogeneous volume of tissue the
bioheat transfer equation takes the form
where
k [W/(m2 . "C)] is heat transfer coefficient between
cooling water and tissue
T, ["C] is cooling water temperature.
Using the Laplace transform the following solution is
obtained:
B
+
. +. -Y
1
where
x [m] is distance from surface
t [ S I is time
T = T(x.I ) [ "C] is tissue temperature
Th I "C] is the temperature of blood entering the region
-
I + -
Y
k
-1
-L :+ - a
(5)
419
KNUOSEN A N D OVERGAARD: IDENTIFICATION OF THERMAL MODEL FOR HUMAN TISSUE
where s is the Laplace operator,
u = Y/P,C,.
Tb
.
and
L'=
j z
(6)
PbcbPim
A s LJm] is the depth where the cooling gain is reduced
I(...-S
&
T
1.ST
T.
Fig. 4. The control model. All model paramnen am lunciions of depth.
by a factor e (see (8) below), we shall denote it as the
penetration depth for surface cooling.
Note that the heating gain is the steady state increase in
The steady state solution (s = O) is
temperature T' per unit power input, when the cooling
water temperature is equal to the blood temperature.
T(X) = K,(X) (T,- Tb) +
fo + Tb
(7)
In block diagram form, the structure is even more eviwhere the cooling gain is
dent (Fig. 4).
For homogeneous tissue K, and Kh can be calculated
Kc(x) =
(8) and (9) i f the tissue parameters and the applicator
from
-,
gain is known. The time constant can be approximated,
I+'
kLc
using (IO), to
-
and the heating gain is
Kh
5=--
Y
B
- Kh
- p,c,L,,eXiLk.
B
(12)
..
I+-
The initial slope of T(.h f ) as response to a unit step input
fo(s)= l/s is
Iv. PARAMETER
ESTIMATION
To estimate the model parameters o f the control model
a corresponding stochastic discrete time model is
used [E].
+
~ ' ( n I ) = e,T'(n) + e2Tf(n- n , )
$. Simularion Model
The time solution T(x, r) can be obtained from ( 5 ) by
inverse Laplace transformation. To obtain a more general
program, capable of simulating inhomogeneous tissue
with temperature dependent blood perfusion. a numerical
method is needed, and a simple finite difference method
has been chosen to implement the computer simulation
model [ 6 ] . In this study. only homogeneous tissue with
constant blood perfusion is simulated.
C. Control Model
+ OJo(n) + (1 + 6,q-I) e ( n + I) (13)
e-"' , e2 = k,(i - e-&"'), e, = kh(l -
where: O, =
e-&'') and T' = T Tb.TE = T, - Tb.AI is the sampling
time, and n indicates the discrete time as f = n . Af. n ,
= round (To/Af)represents the delay. e ( n ) is a white random sequence, and q-' is the backward shift operator.
The last term in (13) represents system noise.
Using the one-step predictor structure [E], 191
-
-
~ h ( n+ I ) = B I ~ ' ( n +
) Bz~:.(n n , )
+ O o ( n ) + &4e(n)
The principal requirement on the control model is a
c(n) = Th(n)
T'(n)
(14)
simple structure and few but significant parameters. A
first-order transfer function plus a time delay for cooling the estimate o f the parameter vector 6 = {81~~&8,)'minimizing the error variance E{&, e)) is determined. As
effect meet this demand:
the
identification is carried out after completion of the
I
treatment, only nonrecursive identification is considered.
T(x. s) =
[K,(x) e-"'""'(T,.(s)
I
s 7(x)
Estimation o f the noise parametere, requires more SamTb(s)) + Kh(x) fds)] f Th(s). (1 1) ples than are obtained during a patient treatment; therefore, 6, ,values are assumed a priori. in the Appendix it
The four control models parameters are
is shown how the remaining parameter vector is dctermined
for Og = O and 8, = 0,. In both cases the delay n,
["C/(w/m')l
heating gain: Kh
is determined by a separate minimum search.
cooling gain: K,
["C/Tl
To evaluate the identified model the model output T,,(~I)
=
B $ : ( n ) + Tb(see (18) i n the Appendix) shall be plortime constant: r
[sl
teú together with the measured data. and the root nrean
time Jeliiy:
r,,
[si.
q u i r e tRMS) rnodcl error
-
+ .
-
.
!
1Ro
TISSUEDATAUSEDIN THE SIMULATION
Paa;&r
1lLIH tym
__+
3.5 , I¡'
0.44
0.029
@.O015
It'
0.44
0.8
, 10''
0.9
m.02~
0.0034
3.5
. 16'
0.M
0.6
. 10''
0.9
o. o29
0.0091
3.5
. 1)'
0.64
0.6 ' 10.'
0.9
0.029
O.OU64
4.0
. it'
0.57
1.0
. IO*'
1.0
0.031
0.0085
4.0
, 10.
0.57
1.0
. IO"
1.0
D.031
0.017
2.0
. 1I'
0.20
0.011. IO-'
0.06
113
0.010
3.5 '
Y
shall be calculated.
v.
IDENTIFICATION OF SIMIJ~(TION MODE&
Based on input-output dam from
the four control model parameters
seven differenttypes of
An experimentally
coefficient between
id[W/m2 TI, is
The power density is calcoiated as
.
From measumments on phantom
cm applicator, values of B and
applicator on skin surface:
B
10 mm water layer: B
rial with a 6 x 4
I
0.1
Lh
B 0.5
3
0.1
Lh
B
.&
L.
3
In the simulations, a 10 mm water la er is assumep.
For identification of the simul~tio
I&) and T&) are step functions. A s 'good
requires weak correlation between t& inputs, the steqs
are not simultaneous.
TlMf Iminl
'k
e;
KNUDSEN AND OVERGA4RD. II>ENTIFICATION OF THERMAL MOUEL FOR HUMAN TISSUE
IHI
I
I,
,
5
O
W
20
40
30
50
M P I W jmmj
DEPTH lmml
O
'
10
7
3
7
-E
3
8
O
o
i ..-
1
0
m
3
0
4
0
5
0
DEPTH Imml
Fig. 6. Estimated contml model panmeten: heating gain Kb,time constant T. cooling gain K.. and delay Y<, four the simulated tissue types listed in Table
I
.
vcmus depth. (Only discrete time-delay valuer T ~ ,= n , ' AI c m be assumed.)
VI.
IDENTIFICATION
BASEDON
PATIENT
DATA
The patient data come from treatment of six patients
with seven tumors; see Table 11. Each tumor has received
from three to six treatments. and a total of 24 treatments
have been analyzed in this study. The recorded data consist o f tissue temperatures measurrd along the central tumor axis
in 4 depths I cm span, in and on both sides of
.
.~
..
the tumor, skin surfwe temperatures in 2-3 locations, and
p w e r delivered to and reflected from the applicator. .As
the cooling water temperature has not been recorded, it is
estimated From the surface temperatures, the temperature
of the water reservoir, and information of water circulation. The sampling time For the tissue temperatures vanes
during the treatment (30-200 s). so to comply with the
idcniiticati«n algorithms. nioditied datasets with constant
lime intervals are generated by means of linear interpolation. The b l w d teniperaturcs are assumed to be equal to
the initial tissue temperaturcs.
The results of rhc identilications are presented 35 p l i m
o f thc cuntrd model pariinicten venus depth. For a m -
T A B L E 11
ANALYZED
PATIENTS AND
I'
65
'
P'iMrY
fvmr
III*
1 ~ 1
tmr
TUMORS
''
q'"b'"fanewr
i"tC.1
hii:010w
'a'on
adc"oc4rc'noma
'OlDn
IdF"OWCl"OM
rnf*lt.I?I
*2
o
E
65
F
'"W'W1
irmpn
"ode
> " 2 i 4 Cn
74
M
n e t t node
>,<.a
61
Y
1"q"in.l'
I i V " "OO.
id",
C.
65
I
'ngvln~l
d ~ i i I t n
1,'4*
cn
iarynX
i m i r n o i d C.rclnOm
.bdWe"
M I > g n . n l in1,nm
Mcl
alignaninelmom
""e
1i
F
weiit
70
M
"CCL
nodi
5iii6
CI
,.<.I
C.
breast
I ~ ~ Q C I I C ~ ~ M L
1.r"""
CD,d.<illld
c,~c,*,,~l
parison the corresponding simulation parameters for four
representative tissue types are replotted as well. Thc heating gain and time conhiant is recorded for six conbccuiivc
trcatrnrnrr o f a tumor in Fig. 7 í 3 ) . The mean and >tdri,l,trd
f
'h/0
5
1
O
zc
Y
'0
5
IO
O
20
30
40
50
40
50
DEPTH lmml
Kh'B
.
,E
--
1
I
I 4
,
U
e
7
0
3
z
0
a
g
2
I '
O
0
'0
20
30
40
50
10
O
DEPTH I mml
*.
L_
-
r.
-.-.
Lr
c
.__
r-
20
30
DEPTHImmJ
Fig. 7. Estimated heating gains and time constants for patients. (a) For six consecutive treatments of tumor F. (b) Mean and standard deviation foi
tumor AI (three treatments). tumor B (six treatments), and tumor F (six treatments).
deviation of Kh and r are recorded for three different tuW e
mors in Fig. 7(b). A s the temperature probe depth vanes
-E
between treatments the mean is based on linear interpoI 3
lation of individual values. The average rms model e m r
for all treatments is O.1o C.
7
The estimated values of cooling gain are mostly unree
2
liable, as they do not decrease with distance, and even
z
negative values are obtained. I n these cases estimation of
J 1
heating gain and time constant is repeated with heating
i
!
power as the only input, ¡.e., the cooling gain is a priori
t
Y
.assumed to be zero. The difference between the estimated
I
heating gain and time constant values with and without
'
2
3
4
5
6
cooling is typically less than 10 percent.
TREATMENT NUMBER
The model parameters have also been plotted as a funC- Fig. 8. Hating gains V C ~ S Utreatment
S
n u n i k r fortumorü. (Depths 5 mm:
O. I5 mm: x.25 mm: O . )
tion of treatment number. Fig. 8 shows the heating gain
for six consecutive weekly treatments of a tumor. The time
constant shows a similar lack of trend.
sponding output temperatures TM of the identified control
Finally, Fig. 9 shows the patient data versus time for a model. The rms model errors are 0.21", 0.15". 0.20",
typical treatment with manual control, and the corre.. and 0.16" for 5 , 15, 25, and 35 mm depths.
,-.
e
í>il>\f
*
A h 0 OVERGi\ARI>
I0I:NTIFICATION O F THERMAL MOOEL FOR HUMAN TISSUE
I
04)
IS
30
45
15
30
45
rc
O
TIME (min)
..
í:i,g. 9. Iiipul power 1.. cooling waler iemperature J. mcarured tissue lcmP:atun:s Tíx) for the founh treatment of t u w r F (depth x = 5 mm:
El, IS mi: @. 25 mm: X . 35 mm: +). and control model output lemp : ~ n : svM:
VIL DISCUSS~ON
AND CONCLUSION
7 he@$ is a good agreement between the control model
oiit iuts and the simulated or measured tissue temperatiirm, as :ieen in Figs. 5 and 9 and from typical rms model
t:lmv values of O. 1-0.2" C. Accordingly, the simple conCrol mcdel structure appears to be adequate. The results
in !;ect.on V show that blood flow variations have a considi:rable effect on the model parameters but, nevertheh!,
the linear control model fits well for real tissue over
il large temperature interval. An explanation may be that
i.he blood Row in most of the treated tumors may not have
e:rc:edt:d the blood Row in resting muscle [IO].
1 he csi.imated values of the heating gain and time constai,t show large variations. For consecutive treatments of
the same tumor the standard deviation of both parameters
is tipically 20-60 percent (Fig. 7 ) . There is no trend in
i,he panimeter values for a specific tumor as the treatment
piuyesses.
111 mosi cases. the cooling water gain and the time delay
could not be estimated froni the patient data. This was due
lo the wriations o f the cmiling water tetriprrature being
tu« small and corre1atr.d w i t h power input. and t o the re-
483
cording of the cooling water temperature being inaccurate. In future systems where the cooling water teniperature shall be used as a computer control variable, both
problems will probably vanish.
The question is now,'which method should be chosen
to determine the parameter values: a calculation based on
a priori assumptions about tissue parameter values or an
estimation based on experimental data? Using the first alternative. the model parameters can be determined as a
weighted average of the parameters for different types of
homogeneous tissue, using the curves in Fig. 6 or the
expressions (8). (9). and (12). It requires a knowledge of
the tissue composition and values of all the parameters in
the theoretical model. In addition, the theoretical model
structure is crucial-Le., the applied bioheat transfers
equation must be a valid mathematical model. The advantage of this method is that it is easy, and that it requires
no treatment data. This is important for prospective and
comparative dosimetry. The disadvantage is the lack of
accuracy. The results in this study seem to indicate that
the theoretically determined parameter values may be off
by a factor of 2-3. There are indications that insufficient
knowledge of the applicator gain contributes significantly
to this lack of accuracy. For example, measurements of
power distribution in phantom material show large variation in B (3) for different water layers, and the applicator
efficiency seems to vary as very hot applicators have been
experienced during some patient treatments. Another crucia1 parameter is the blood perfusion; the physical interpretation of the blood flow rate m in ( I ) is questionable,
and the values given in the literature show large variations. Accordingly,
- . an accurate a r>rioridetermination o f
the control model parameters
studies of
the validity of the applied a priori assumptions.
The experimental method only requires that the structure of the control model is reasonable. The structure of
experimental models is generally far less crucial than the
StNcture of theoretical models. Consequently, the method
has two distinct advantages: it is accurate, and it requires
no a priori knowledge of patient anatomy, tissue parameters, applicator gain, etc. The main disadvantage is that
it can only be employed during and after treatments.
When the purpose of the model is to determine the parameters in feedback control algorithms (concurrent dosimetry), the identification must be performed on line in
the beginning of each treatment. This constitutes a selftuning or adaptive controller. as described in [ I 11 and
[ 121. I f further studies reveal that time dependent control
model parameters are appropriate to reflect variations in
blood perfusion, a recursive parameter estimation must be
performed during the complete treatment.
In reference to the stated purpose nf this study the conclusion is
-the stmeture o f the control model i?i adequate:
-the niodel parameter values for homogeneouh tksue,
determined from <I priori assumed parameter \slues hy
identitication o f the siniulation model 2nd by an.d)tical
calculaii~iii. b h o u good ~ i i u t u a lagrwtiteni. hiit \ t i t t i ihc
:
..
.,
.
--
IIII
4k-1
IY.\P,\A<
IIO,,
,>L.
h l ~ ! \ ~ l\ Ii ~I lV~, , I ~ I I . ~ I ~ , .\,>I W I t
i
i\ I )
5. V A \ l w h
available II priori knowledge. they do not accurately re- and thc gradient vector and H w i m matrix a f t
produce the experimentally estimated values:
N
2
-for the analyzed patient treatments. the heating gains
c(e)= -- C (T'OO - r;,(w~ ( 1 1 .e)
N.=i
and the time constant have heen estimated. The results
show large variations even for consecutive treatments of
N
2
the same tumor. A reliable estimation of cooling gain and
H(e) z R(e) = 2; ~ ( r i .e) +'<ri. e).
time delay requires a more vigorous variation of the coolN.-i
ing water temperature.
The parameter vector is then determined iteratively from
-approximate values for the control model parameters
can easily be calculated. If. however, an accurate model
0 . = 0 c..). - (W, + p , E ) - ' G , .
(20)
is required, an identification in each treatment based on
experimental data is recommended.
E is the unit matrix. Small values of p give fast convergence, as p = O corresponds to a Newton iteration, and P
APPENDIX
= m to steepest descent.
PARAMETER
ESTIMATION
I f the noise sequence e ( n ) is Gaussian, a maximum
An estimate of the parameter vector 0 = {ol&&}r in likelihood estimation is obtained by the Markov method.
the discrete time model (13) is determined for two special' In both methods. the delay nl is determined by a separate
cases of the prediction enor method [ 9 ] . The two cases minimUm search as the integer giving minimum Vahe O f
correspond to two specific u priori assumptions about the the performance index.
noise.
ACKNOWLEDGMENT
-9, = O gives the simple least squares method, where 6
can be found analytically.
Significant parts of the work behind this study have been
Introducing the signal vector
In particular we are grateful to
done in student projects.
. .
J.
E.
Duhn
who
constructed
the identification program.
{T'(,,- 1) T : ( ~- - 1) lo(n(15)
-
a performance index, equal to an estimate of the mean
square error, can be written
N
N
1
1
&n) = - C
Nn=i
N n = l
p(e) = - C
- ~ y n ) ) * . (16)
A s v, is independent of 8, the value 6 minimizing (16)
can be found analytically as
(17)
6 = -H-'Gío)
where the gradient vector is
and the Hessian matrix is
H=B4 = 0, leads to the Markov method.
iTL(" -
Tf(n -
'1
A s the signal vector
- I ) 'o@
- I)}'
(18)
is now a function Of the
be determined analytically.
W e now introduce +II as
minimizing(16) cannot
. .
a
a
v(n, e) = ) - ( e h n , e))
ae T L ( ~ =
ae
=(D~oI,
e) +
W . Stmhbehn and R. B. Rocmcr. "A S Y T V C ~of computer Simulations of hyperthermia tma~menis." IEEE Trans. Bioitwd. Eng., vol.
I l l I.
BME-31. pp. 136-149, 1984.
121 P. M. van den Berg c l al., "A compulatianal model of the elcclmmagnetic heating ofbiological tissuc with applicalion IO hyperthermia
canccrthcrapy," IEEE Trans. Biomrd. Eng., vol. BME-30. pp. 797805, 1983.
131 U. van Slicdrcgt. "Compuier cilculaiians of a one-dimensional
model. useful in the application of hypenhermia." Micro~wveJ . , pp.
113-126, June 1983.
141 1. B. Andenen e l al.. "A hypenhcrniia system using a new type of
inductive applicator." IEEE Trans. Biomrd. Eng., vol. BME-31, pp.
21-27, 1984.
IS] I. B. Andenen, "Thcorctical limitations on radiation into muscle tissue," Inl. J. Hypcnhcrmiu. vol. I . n o I. pp. 45-55. 1985.
161 M. Knudsen and L. Hcinzl. "Hypenhemis cancer therapy: Modelling, parameter estimaiian and ciinin>tof icmperatum disiribution in
human tissue." in Proc. 1 1 t h IFlP COMJS.ysr. Model Opiirnizolion.
DO. 709-716. 1984.
171 H. P. Schwan and K. R. Foster. "RF-field interactions with biological systems: Electrical pmpenies and biophysical mechanisms."
Proc. IEEE. vol. 68, pp. IW-113. Jan. 1980.
IS] K. J. Astmm. Inirodurrion IO Srorh,~riii.Conrrol 7hto-.
New York:
Academic. PP. 162-179. ~ 8 0 .
191
"Maximum likelihood and prcdiriion emor melhds." AUIOmarira, vol. 16. pp. 551-574. 1980.
[ I O ] I. W. Strohbehn, CI o/.. '' Blood Row ciiecis on ihc i c r n p e r a t k dirtñbulion fmm an invasive m i c m w w mtcnna a m y used in cancer
therapy." IEEE Trons. Bioinrd. E t q . . vol. BME-29, pp. 649-661.
1982.
( 1 I]
M. Knudrcn, et 01. , "Hypenhem)ia system with self-iuning coniml
of temperature disirihuiion in I~SSUC:' in Proc. 4rh /ni. S?mp. H?.
perrhermie f l ~ l c o l o ~vol.
y. I .
London. England: Taylor and Fnnc i s , 1984. pp. 691-694.
1121 M . Knudsen and L. Heinzl, "Two-pin1 coniml oficmperaium profile in lissue." submitted to In,, J. Hyp<.rrhrrmio.
1131 R . B. Roemec. "Thermal modelling." in Prrir. 4rh /ni. Symp. H y
perihmnic flncolop. val. 2. London. England: Taylor and Francis. 1985. pp. 293-298.
..
N
vz(n9 e)
REFERENCES
elW(n
-
I,
e)
(19)
-.
KY1Jl)'ihN A N > ,.>YBRGt\.4Rl> I1)ENTIFICATION OF THERMAL MOI>EL FOR HUMAN TISSUE
>lwtm linudsen received the M.S. degree in
dectricil engineering from the Technical Umversity of Denmark. Copenhagen, in 1963.
From 1965 to 1968 he was with the Selva Lab-
485
Jens Overgaard war born on November 27. 1945.
He graduated from the Univcrjiiy of Aarhur hirdical School. Aarhus. Denmark, in 1971.
Fmm 1971 to 1976 he trained in clinical medicine and in cell and radiation biology. Fmm 1976
u> 1977 hc was a resident in ndiation medicine at
oniiiry. Tcchnical University of Denmark. From
1968 lo 1969 he was a Systems Enginem at General Dynamics, Rochester, NY. and from 1969 to
Massachurenr General Hospital. Boston. MA, and
1971hc was implcmentingcomputcrcontn>lin the
was a Clinical Fellow in radiation therapy at Harpapcc industry with Measurex Corporation. Santa
vnrd Medical School, Cambridge. Cumntly he is
Clan. CA. Since 1971 he has been an Associate
Headof the Seclion of Expcrimental Oncolow and
Profcisor of Control Engineering at the institute
Radiotherapy, the InstiNte of Cancer Research.
01 Elzcironic Systems. Aalborg University, Aalborg. Denmark. His lnain Radiumstationen. Aarhus. H e has participated in clinical and fundamenial
i i i t c ~ ~ shave
t s been modeling. identification and contml o f energy pmduc- research in hyperthermia and cancer treatment since 1969.
¡rig and distrihuting system%and in recent ycan of cancer hyperthemia
Dr.Overgaard is President o f European Society for Hyperthermic on.
sirlenis.
cology. and was Chairman of the organizing committee for the 4th International Symposium on Hyperthcmic Oncology, Aarhus, 1984.
i
"
.
l
.
1
.
."..
^.
I
.
,._.
*-.,
d.
k.
4.
i r o i t s k i i , A.
Gustov,
,,>rt>aChev, L.
Siz'minh.
! , >'
'lechkov, E. A ' Aransher+v.
OladyshMina,
I , I; i:obrynina, A.
i i i
. A. Odintsov
> . :i
' . i'
f.idl.
ctiermometry bas
: ) : I e! e;tromagnetic
:
frequadcy raage of tile , i n t e r n a l
i n t e 4 i t y of the r a , i i q e d s s i o n s of
ure of $&adiating
La3ers: is being
tmEe +es
i t possibte ; t o -sure
to
the penetrat:.q depdh o f the
contea4 at wavelengths 'froca 1 t o 30
to '1 O.& .lo,
and qor layers with 4 low water
is tw wavelendth in a vacuum . Thus f o r
o f tw human bddy a t a wavelendth of 30 cm
-
t e
:e.i .t
Corky/Sdent
a wavelength
i
.: oi n antenna, a r
I:,.
:nta t antenna is
1 i I r ,vid d b y a quarter
e - . , .c:ic
~
, f the antenn
5,:
I'-i u r f ~ c z
boundary is
a ? ':ir:
f the antenn
1.t
:'I.
'
~
'h
iadiometer i s
a fcsquency o f 9
Fti
:; .gial , modulated w i
8: ' . b i g o : 3 p a r e m t r i c
t i
:,irim tc.ic amplifie
01: ; Y based on a
0 . 1 . i i r c u i t which
oh' ' : f a t i . n time constant
pi'
:'o a K;P = 4 potenti
(If
t'.e radioueter
t.
if.
I
I .
.#O i i . v m t i g a t e p a i
,[l . 'Fie mx;t valuable
ab!'
ll'itmi!
:BLues o.f dept
1':i:uea : y is achieve
I! i f w : ,of the powe
1*?i !. ( ! r ? o . : . Variation
I:
(3 i' :I ?,eral degre
;"l1 *
l
'tliai:
) oven taking
8i' '': 'h?
:-<,<'ired accu
0 : :'?(luce by an
ii.Liiai:i i n . This í
' X : O : ';md
~
from t
(:uLt :I> guarantee
I
'iii:.t,zai.
n
'? ( I d i f f e r s í
thi
~
.-.-~
...,.,-
-._
';'n rk:, ~idiopliysic
Ir-,'l.':;ll Ill 3t:itute of t
3
'r'?kii:x.k-i,No.
3,
twiq
Resejarch Iqstitute I p d i c a l radiot:hepmonieter which
dtgloped; The rad&thermmetríc co)npleX coni t , and radic-emissím c a l i b r a t o r s .
line. b t c h i n g t o t1.e human body
lancing( loop of simi1.aa size^. The
ion w k f f i c i e n t R at. the antenna/
ge 4 d de*&
on the nature of the: tkssues. The
ch provides d i m c t amplificas given i n I'igl. 1. The infrequency é.r+ifier contween the nlo+lator and
14 type. The, quadratic
ion of the ra(liorPter.
engineering, ha@ two
rom O t c 30 dB and outr. The fluctfution thrarihof 4 sec is 0.025"C.
depth temperpure i s used
that of d e t e h i n f n g the
an +O.icC.
This l e v e l
i c u l t i e s ahd above a l l
undary on the measure25 range r(su1t i n an
Researcb r e s u l t s have
mation formulp does not
ake i t possi)ie t o e i i e
of R on th& temperature
o f reflection from the
[3].
But i t is q u i t e
of the bodf p a r í s being
¡
.
S . II. Kirov
aaslated from W d i t s i r i r
z i r t e d S'pdember 28.
R. and the
'
i
a
Fig. 1. Block diagram o f the radiometer.
1) Antenna; 2 ) c i r c u l a t o r ; 3) modulator;
4) c i r c u l a t o r ; 5) parametric a m p l i f i e r ;
6) t r a n s i s t o r a m p l i f i e r ; 7) quadratic
d e t e c t o r ; 8) low-frequency iinit; 9) KSP-4
p r i n t e r ; 10) n o i s e g e n e r a t o r ; 11) attenuator;
12) minicomputer; 13) power unit.
A method i s proposed i n [4] i n which t h e e f f e c t o f R on t h e r e s u l t s o f t h e measurement
o f temperature i s s i g n i f i c a n t l y weakened.
For the sake of s i m p l i c i t y l e t us assume that t h
antenna does not have loss and d i s p e r s i o n .
I n that case the radiothermometer r e g i s t e r s
nitudes which a r e p r o p o r t i o n a l t o t h e e x p r e s s i o n T, - T,R + TnR, where T, i s t h e average
temperature,whereT=R i s t h e r e f l e c t e d s i g n a l from the antennalbody boundary, and TnR i s
s i g n a l a r i s i n g from r e f l e c t i o n o f i n t e r n a l n o i s e from the same boundary.
It i s apparent
t h e expression t h a t i f t h e temperature o f the input elements o f the radiometer and theavera
temperature of t h e o b j e c t b e i n g measured a r e kept equal (Ta
Tn), i . e . , i f thermodynamic
e q u i l i b r i u m i s maintained, then t h e decrease of t h e useful s i g n a l by an amount TaR w i l l be
During t h e mcasurement t h r . Lempercompensated by i n t e r n a l n o i s e r e f l e c t e d from t h e boundary.
a t u r e o f t h e input d e v i c e s and one of t h e c a l i b r a t o r s is kept approximately equal t o the
average temperature o f t h e body. E r r o r due t o mismatching under these c o n d i t i o n s Of approxi
mate thermodynamic e q u i l i b r i u m does n o t exceed 0.1"C.
-
i
lbo r a d i o emission c a l i b r a t o r s were used t o c a l i b r a t e t h e s i g n a l : water heated t o tem- 1
,'
peratures o f 33 and 36'C and contained i n thermostats of the Ti.-150 type.
A f t e r recording
o f t h e c a l i b r a t i o n t h e antenna w a s p l a c e d on t h e area t o be i n v e s t i g a t e d and t h e radiometer
4
s i g n a l was recorded.
the the method described above was t e s t e d by means o f measurements, using a radiothermometer
and a mercury c a l i b r a t i n g thermometer, o f t h e temperature of human t i s s u e e q u i v a l e n t s . Their
r e s u l t s coincided w i t h an accuracy o f ?0.loC.
I n l i v i n g tissue w i t h a temperature gradient
the radiometer measures an averaged temperature o f t h e r a d i a t i n g l a y e r s , which, f o r t h e head,
i s 1-1.5OC lower than t h e depth temperature. This was confirmed experimentally by radioand electrothermometer measurements o f c r a n i o c e r e b r a l temperature during ventriculography.
We have been using t h i s new noninvasive method f o r a number of years i n c l i n i c a l p r a c t i o
t o i n v e s t i g a t e average depth temperatures.
The r e s u l t s o f t h e examination o f 300 p a t i e n t s
s u f f e r i n g from i l l n e s s e s o f t h e nervous system and i n t e r n a l organs t e s t i f y t o t h e valuable
d i a g n o s t i c p o s s i b i l i t i e s o f t h e radiothermometric method [ 2 ]
.
LITERATURE CITED
1.
2.
3.
4.
80
A. B a r r e t t and P. Myers, Science,
V. S. T m i t s k i i , A. V. Gustov, I.
12, 669-671
(1975).
F. Belov, e t a l . , Usp. F i z . Nauk.,
(1981).
V. S . T r o i t s k i i , V. I. Abramov, I. F. B e l o v , e t a l . ,
R a d i o f i z i k a , 24, No. 1, 118-121 (1981).
V. S. T r o i t s k i i , i b i d . . 2, No. 9, 1054-1061.
g,
No.
1, 155-158
I z v . Vysch. Uchebn. Zaved..
,
405
iEEE TRANSACTIONS ON BIOMEDICAL E f f i l N E W f f i . VOL. BMI-33. NO 4. APRIL I986
Aberrant Heating: A Problem in Regional
Hyperthermia
MARK J. HAGMANN,
MWBER,
IEEE. AND
ffi
RONALD L. LEVIN
a mannequin filled with tissue-equivalent phantom material. The measured rate of energy deposition (specific absorption rate, or SAR) in the neck war found to be 2.2
times that in the abdomen when the APA was positioned
for abdominal heating [7], [SI. The local SAR in the neck
was reduced to 30 percent of that in the abdomen when a
and 580 MHi. The local ntu of rnerl(y
saline-@led bolus was placed around the neck of the mane h n t . and thlsb oftan exceed that In the
omen. TIN P*<m
düir
nequin
171. In clinical tests made with the APA, a salineihcrnnt healing Is dependent upon the WiitioM of Ue arbs OIÚl2p.
filled
pillow
is usually placed under the patient’s head and
~ h c r n nheating
t
appears te hc much les# prososirrd fer tre4tmcnt
neck to d u c e neck heating and improve patient comfort
of the thigh or upper arm than it is for tr(atiMn< d the .Mown.
[8]. In other tests, when a helical coil applicator was used
to heat one thigh of a mannequin filled with tissue-equivI. INTRODUCTION
alent phantom material, the deposition measured in the
PERTHERMIA has shown considcrnble pmrnise cmtch exceeded that in the thigh [SI.Another phenomefor the adjuvant treatment oficancer, but ii is esen- non that could not be evaluated without realistic threetia1 that the heat be delivered to the tumor region with a dimensional modeling is the localized surface heating that
high degree of precision [l]. IQeaiiy the tanperanire has been measured near the tapered waist of a female
throughout the volume of both the tumor and the sur- model when heated with the APA [71, [IO].
rounding normal tissue would be known so that one could
Numerical sotutigns obtained using block models of
determine the degree of uniformity of treatment to the tu- man have been used in the evaluation of biological hazmor and also estimate the extent ‘of possible damage to ards from exposure to electromagnetic fields [ i l l , [12].
the normal tissue. In practice temperanire p m k are used These selutions have predicted several experimentally obfor measurements at only a few iltracavity or intet)tliiai served phenomena including selective heating of the neck
locations. The degree of sampling may be somewhat in- [I21 and head resonance [13], as well as the enhancement
creased by moving a probe locrted within a peicdta- of energy deposition due to the ground and reflectors [ 141
neously placed catheter [Z] or by using temperatun probes or by one or more other bodies [15].
having multiple sensors [31.
We believe that quantitative treatment by hyperthermia
11. METHODS
requires the use of electromagnetit and thermal modeling
In this paper we have continued to use the 180 cell block
for estimation of the temperatuniat locations other than
those where the probes are located. This is particularly model of man as shown in Fig. 1, which was developed
important when frequencies below 1GHz arc used M treat earlier by one of IS (Hagmann) [ 1 I], [12]. The cubical
deep-seated tumors, since depositbn is not as localized at cells of the model have various sizes and are arranged for
such frequencies. Others have used two-dhensional-ekc- a best fit of diagrams of the 50th percentile standard man.
tromagnetic modeling in attempts;to characterize the en- A partial correction for dielectric inhomogeneities is made
ergy deposition in a cross section:of the body duriig hy- by using a volume-weighted complex permittivity for each
perthermia [4]-[6]. Realistic three-dimensional modeling, cubical cell based on the partitioning of 12 different types
however, is needed to explain the phenomenon of aber- of tissue throughout the body.
Thus far, we have considered only idealized applicators
rant heating. which we define to bC energy dapasition eutside the region intended for treatpent. Abermnt heating in order to highlight the effects of aberrant heating. We
of the neck has been observed in measurements made have made the appmximation that the incident electric
when a BSD annular phased array (APA) was uced to heal fKld has constant magnitude and orientation within the
expose4 volume and is zero elsewhere throughout the
Minurcnpt received (kioober 29. iQR4: *vised S e p ~ e r n b a18. 1985.
body. Thus, deposition of energy throughout the rest of
The ruthon un: with the Biomrdicrl Enginunng and Immrnoniition
the body occurs only by means of scattering from the exI4rrnr.h. D i \ i h n uf R s x a x h knicsa. National initiiuies of Heiihh. i
k.
posed
volume. If the incident electric %Id is nonzero outiherdr. M D : O N 5
side the volume chosen for treatment, then aberrant heatIEEE~ . ~ ~* up m h c XJO~ISS
r
A b w l - A 100 cell block ntvdel of myI b u ka und to cuepte
the pittern of energy deposition w k n r&-frwtfCnicy ip)l*itglire
used for irutment of cancer hy hyperthqmia. When the iLdohan ir
exposed with p o h r h t b n praliel to the
h of the hody at g*lWneics from 10 to ó0 MH.,ipproKimma)y
M c.mal ol tb toW ene r g l ir deposited outride of lhe ahdomen. Whb I r r l i o n ir InurW to
u much u W p e r m 1 at several resonanbs whkh 9cco1 betweCa 1W
r
rm‘nmC-RH
w
U.S. Gokernrnsnt work not protected by U.S. copyrixht
Y
a
E
F R T O W K I (11HZ. >
Fig. 2. Whole and regionrl SAR for plane-wavc crposurc head dotted.
lower a m dashed. mean solid.
Fig. 1. Realistic block model of man showing regions
ing will tend to be more pronounced than is shown in the
present calculations for idealized applicators. For example, when the APA is positioned for abdominal heating of
a phantom-filled mannequin, the aberrant neck heating is
significantly increased i f the water bolus about the abdomen is deflated (71. Since the water bolus serves to confine the incident electric field to the abdomen, the incident
electric field at the neck is greatly increased by deflation
of the bolus and so the neck heating is increased.
W e have not attempted to address the issue of local deposition since a block model with much greater detail would
be required before the values o f deposition at various
points could be obtained with accuracy. The volume average deposition was evaluated in the head, neck, upper
arm, lower arm, upper torso, lower torso, upper leg, and
lower leg, with these eight body regions defined for the
model as shown in Fig. 1. The lack of symmetry in solutions for exposure of one thigh or upper arm required
that 1 6 body regions be used since the calculated values
of deposition were different in the left and right halves of
the model.
Fig. 2 shows the frequency dependence of the average
and local SAR for exposure of the model shown in Fig. 1
to a plane-wave having Z polarization (parallel to the
length of the body) and a time-average power density of
1 mWlcm2. The phenomena of head and arm resonance,
which are apparent in Fig. 2 , have been described previously 1131, 1151. Resonances are also present in the following figures of this paper which pertain to exposure with
idealized hyperthermia applicators. The calculations for
each figure were made using a total of 96 frequencies from
IO to IO00 MHz in order to illustrate the pronounced dependence of energy deposition on frequency.
111. RESULTSAND DISCUSSION
A. Abdominal Exposure
Fig. 3 shows two different block models that were used
in order to determine the possible effects o f limb positions
on aberrant heating. In pose I , which is the same as Fig.
1. the arms are down at the sides and the feet are together.
In pose I1 the arms extend outward from the sides and the
centers of the feet are 100 cm apart. The cubical cells in
which the incident field is present have been darkened in
Fig. 3. Calculations were made for three different onentations of the incident electric field. The Z polarization,
with the incident electric field parallel to the length of the
body, approximates the AYA. The X and Y polarizations
correspond to anterior-posterior and left-right onentations, respectively, which approximate exposure with
parallel-plate (capacitive) applicators [ 161.
Figs. 4 and 5 show the frequency-dependence of the
fraction of the total heat dose that is delivered to the exposed ponion of the abdomen using poses I and 11, respectively. The two figures suggest that aberrant heating
is strongly dependent upon the positions of the limbs and
is generally most pronounced for the case o f Z polarization.
The frequency-dependence shown in Figs. 4 and 5 may
be summarized as follows. Below 60 MHz, the fraction
is not sensitive to frequency, and for Z polarization, approximately 60-70 percent of the total heat dose occurs
outside of the abdominal region. Aberrant deposition is
most pronounced at various resonances between 100 and
500 MHz, where as much as 90 percent of the total energy
deposition occurs outside of the abdomen. These resonances are dependent upon the positions of the a b s and
legs. At frequencies well above 500 MHz, the deposition
is localized due to the high absorption in tissue. Microwave applicators are known to provide localized treatment, but the relatively shallow penetration of tissue generally restricts their use to treatment of superficial tumors
1171. Deep-seated tumors can only be treated at microwave frequencies by the use of interstitial or intracavity
applicators (181, [IS]. It should be noted that the block
model solutions are likely to have appreciable error at frequencies equal to or greater than those corresponding to
the extreme right-hand side of the two figures 1201.
Table I gives the ratios of regional SAR to that in the
407
HAGMANN AND LEVIN: ABERRANT HEATNCl
Fig. 3. T m poses used fot exposum of abdomen.
TABLE I
APPIIOXIWATE
RATIOS OF &GIONAL DEWSlTION TO THATIN THE ABDOMEN
8
I
a
C
r
1 6
-
e 4
-
I
E
AT L O W PLEQUENCIES FOR
.".--...U p p a r Arm
L w a r Arm
Upper Torno
upp.r
X
Lar.,
E
O
I 2
-
'1
r
R
f
A
O B
I
#
LO,
Le,
,111
.45
.34
.47
.o1
TABLE 11
2
3
.
I
5 6 78)
2
102
FRIPUfKI <fWZ >
3
4
ABWMEN
1
B.d,
Ils*ion
Heid
Neck
U p p e r Arm
L o r i r Arm
u p p e r TOI.0
u p p e r Le>
8
0 7 1
.iP
2.47
.I1
.64
.16
WORST-CASE RATIOS OF REOIONAL DEWSITION TO THATIN THE
POR ALL~ E Q U E N C I EAND
S
POLARIZATIONS
Fig. 4. Fraction dcpsiiian in c r p w d volume for pose I.
i
a
z POLARRATION
1
L-ir
Le,
PO'<
1.1
3.1
4.4
5.9
4.1
1.7
1.6.
I
I1
?O..
1.0
3.1
4.b
4.4
1.9
1.9.
o
45
!
I
?
I
I
I)
f
x
r
O
I
D
R
exposed pan of the abdomen at IO MHz with both @$es
for the case of 2 polaritation. The rdtios are all much
lower for the other polarizations at frequenc¡es,below 60
MHr The large dilfcrcnce bctueen b a l u e h for the lower
arm in the two pose6 is attributed to the difference in distance fmm the applicator. The SAR in the legs is also
significantly different in the two poses.
Table I1 gives the worst-case (maximum) ratios of regional SAR to that in the exposed pari of the abdomen for
all frequencies (10-io00 MHz) and all three polarizations. In all except two cases which are noted in the table,
~ 2 polarization, and in the two
the worst case O C C U ? ~for
exceptions the valuer for Zpolanzations were only slightly
less than the worst case. The values in Table 1
1are considerably greater than those in Table i, showing the pmnounced effects o f vanous resonances. Worst-case values
are significantly less for pose II than for pose I in the upper torso, lower arm. upper leg, and lower leg.
Fig>. 6 and 7 shou the ratio o f average SAR in the neck
to thdt in the enpo\ed ponion of the ahdomen for pose> I
1
o
Y
I
n
E
II
S
n
!
i
P
O
S
E
O
n
E
a
N
6
a
I
FIZOLWCY CHHZ.
FREOLKKV <nH1.1
Fig. 6. Ratio of heating in neck to exposed abdomen for pose 1 polanutionr: X dotted. Y dashed, Z solid.
>
Fig. 8. Ratio of hating in lower innIO exposed abdomen for pose I poIafiutianr: X dotted, Y dashed, Z solid.
I
L
F I E W E I C Y < U r n .>
FREWEKV < M Z . >
Fig. 7. Ratio of hating in neck to exposed abdomen for pose 11polan.
utians: Xdoncd, Y dashed, Zsolid.
and 11, respectively. It may be seen in the two figures that,
as noted in Table 11, for the worst cases of frequency and
polarization the average SAR in the neck is somewhat
greater than three times that in the abdomen with either
of the two poses. The two figures also show a pronounced
difference in the frequency-dependencein the two poses.
For example, the maximum ratio occurs at 300 MHz with
pose I and 170 MHz in pose U.
Figs. 8 and 9 show the ratio of average SAR in the
lower arm to that in the exposed portion of the abdomen
using poses I and 11, respectively. Tables I and 11 show
that, either at 10 MHz or for worst-case conditions, aberrant heating is most pronounced in the arm. The two figIIRS each have a maximum near 150 MHz where arm resonance may be seen in Fig. 2 for plane-wave exposure.
A second resonance near 300 MHz is just visible with
pose I1 but dominates the lower frequency resonance with
pose I.
Fig. 9. Ratio of heating in lower ann to exposed abdomen for pose I1 polarizations: X doltcd. Y dashed. Z solid.
B. A m Erposure
Fig. 10 shows the block model used for evaluation of
aberrant heating with exposure of the right upper arm.
Calculations were only made for the incident field polarized parallel to the axis of the arm. Table I11 presents the
worst-case ratios of regional SAR to that in the exposed
portion of the right upper arm for frequencies from 10 to
10oO MHz. Aberrant heating appears to be much less pronounced than was found for exposure of the abdomen.
Over the entire frequency range used for the calculations,
the average SAR in each region outside of the right arm
was less than 30 percent of that in the exposed region.
Over the first decade in frequency, from 10 to 100 M.Hz,
all regions except the right lower arm have values of average SAR that are less than 8 percent of that in the exposed region.
Fig. 11shows the ratio of average SAR in the right
lower arm to that in the exposed pari of the right upper
,,,
,
409
i4 ',,;Y,6Ir11 .&P.ID LEVIN: ABER.RANT HEATING
Fig. 12. Block model with thigh exposure.
Fig. IO. B l o c k model with ann exposure
TABLE 111
WoiIST..CAsE RATIOSOFREGIONAL
DEPOSITION TOTHAT IN T H E
UPPER A R M FOR ALL FRWUENCIES
Bod, R e l o p i
Heid ? L e í , >
Heid ( R i g h t 1
Neck ( L c f I )
NrcL ( R i g h t 1
L e f r U p p e r Arm
L i f t L o w r r Arm
R i g h t Lower Aim
L e f t Upper Toiio
R i g h i U p p e r Torso
. .,
L e f t L o w e r Torso
R i g h t L o w c r Tali0
L e f t upper Leg
R i g h i Upper Leg
L t f t Lower L l g
R i g h i Lower Leg
. ,
..
RIGHT
RltiO
.14
.14
.19
.12
.12
-18
1.16
.os
.I3
.o4
. O8
.o3
.os
.o1
.o3
II
I
L
o
Y
E
R
,
I.
...
...
n
R
II
S
n
!
E
X
P
O
s
..I
...
-...
E
Q
"
i
....
lhg. I I . Ratio oí healing in h g h i lower n m IO exposed hghi upper a m .
..
ii,imi'oir
- ..
.
<.
TABLE 1V
RATIOSOF REGIONAL
DEPOSITION
FOR
TO THATIN
ALL FREQUENCIES
R.ti0
Body Region
Head ( L c f r l
Head ( R i g h t 1
Nick ( L c f r l
Neck ( R i g h t 1
L e f t U p p e r Arm
R i g h i U p p e r Arm
L c f t Lower Aim
R i g h t L o w e r Arm
L e f t U p p r r Torso
R i g h t U p p r i Torso
L i f t L o w e r Tor10
R i g h t Lower
RIGHTTHIGH
Torso
L e f t upper Leg
L i f t Lower Leg
R i g h t Lower Leg
.I3
.I3
.41
.44
.a1
.34
.10
.53
.16
.35
.22
.29
.35
.14
.38
nounced than for exposure of the abdomen, the possibility
of greater heating in the lower arm than in the exposed
upper arm certainly needs to be considered in clinical applications.
. .
.. .
WORST-CASE
the block model in Fig. IO. The ratio has a max-
iriuni of 2.16 at 330 MHz and a value of approximately
I:) 8 from IO to 100 MHz. While the exposure in regions
cI,stant from the applicator appears to be much less pro-
C. niigh Exposure
Fig. 12 shows the block model used for evaluation of
aberrant heating with exposure of the right thigh. Calculations were only made for the incident field polarized
parallel to the axis of the leg. Table IV presenfs the worstcase ratios of regional SAR to that in the exposed portion
of the right thigh for frequencies from IO to IO00 MHz.
Aberrant heating appears to be much less pronounced than
was found for exposure of the abdomen, but is more evident than for exposure of the right upper a m .
Most of the large ratios in Table IV occur at frequencies
of 200 MHz or greater. For example. the ratio of average
SAR for either side of the neck is less than 9 percent of
that in the exposed part of the right thigh for frequencies
from 10 to 170 MHz. Over the first decade i n frequency.
from 10 to 100 MHz, the ratio of regional SAR to that in
the exposed portion has a maximum of O.19 i n the right
lower torso and does not exceed 0.16 in the other regions.
Aberrant deposition may present a problem in treatment
of the thigh at frequencies of 200 MHz or greater, but the
extent o f that problem appears to be significantly less than
that for treatment of the abdomen.
IV . CONCLUSIONS
When radio-frequency energy is used to induce hyperthermia, much of the heating may occur outside the
region intended for treatment. Such aberrant heating is
likely to go undetected during a treatment session since
there are PractjFal limits on the number of temperature
probes that m?y be used. For this reason we would
strongly recommend that patient complaints regarding
heating in varibus parts o f the body be taken seriously.
Our results suggest that aberrant heating may generally
be minimized by avoiding the use of frequencies in the
resonance region which occurs from approximately 100500 MHz. In all calculations made for exposure of the
abdomen, arm, and thigh, relatively low and stable values
o f aberrant deposition were found at frequencies below 60
MHz. Another possibility is to use microwave frequencies for which the deposition is highly localized due to
shallow penetration o f tissue.
In some cases there may be a conflict between minimizing aberrant heating and other important factors. For
example, when treating a portion of the human arm, efficient coupling of energy to the arm would be expected
to occur at arm resonance. Since arm resonance is a manifestation o f the interaction o f the fields with the arm as a
whole, the deposition is not well localized. As a second
example, for the case of exposure of the abdomen, it appears that aberrant heating may be minimized by the use
of other than 2 polarization. Parallel-plate (capacitive)
applicators would provide these polarizations but are
known to cause excessive heating o f the fat layers f161.
The azimuthal polarization obtained with the Magnetrode
would also be likely to limit aberrant heating, but this
applicator is also known to provide little deposition near
the body axis [Zl].
It is suggested that mannequin-shaped phantoms would
often be more appropriate than phantoms having less realistic shapes for the experimental evaluation of radio-frequency applicators intended for use in hyperthermia. Since
our calculations suggest that the positions o f the limbs
will alter aberrant deposition, it would be best for the
models to have arms and legs in positions typical of those
during treatment.
ACKNOWLEDGMENT
The authors are grateful to Dr. E. J. Glaistein, Chief,
Radiation Oncology Branch, COPIDCTINCI, for continued support and encouragement. Dr. Glatstein first suggested the phrase “aberrant heating” to describe the phenomena which are discussed in this paper. The authors
also appreciate the assistance of R. O . Creccy o f ROB/
COP/DCT/NCI.
REFERENCES
[ I ] 0 . U. Hahn. “Hypcnhermia lor Ihr cnginccr: A shon biological
primer.” /€€E Tmnr. Bioiomrd. En*.. vol. BME-31, pp. 3-8. Jan.
1904.
121 F. A . Gibbs. Ir.. M. D. Sapozink. K . S. Gates. and J . R . Sicwan.
“Regional hypcnhemia with an annular phased a m y in the erperimentnl treatmenl of c.ncc~. Repon of work in pmgresr with a tcchnical emphasis.” IEEE Tronr. Biomed. Eng. vol. BME-31. pp. I 15119. Ian. 1984.
131 V. A . Vaguinc. D. A . Christensen. I . H.Lindlcy. a n d T . E. Walston.
“Multiple sensor optical thcrmomiry system for application in clinical hyperthermia.” IEEE Trans. Biomrd. Eng., vol. BME-31, pp.
168-¡12. h.
1984.
141
. - U. F. Iskander. P . F. Turner. J. B. DuBow. and I. Kao. “Twodimensional technique IO C B I C U I ~ ~ Cthe EM power deposition pattern
in the human body.” 1. Miernww POMI. vol. 17. pp. 175-185.
Sept. 1982.
I51 P . M . Van Den Berg. A . T. De H m p . A . Segal, and N . Prnagman,
“A computational d e l of the clcctmmP@tctie heating of biological
tissue with application to hyperthermic cancertherapy.” IEEE Trans.
Biomcd. Eng.. vol. BME-30, pp. 797-805. Dec. 1983.
16) O. Arcangcli. P. P. Lombirdini, G. A . Lovisolo. G..Marsiglis. and
M. Piatelti. ”Focusing of 915 MHz electmmagnctic power on deep
human tissues: A mathematical model study.” IEEE Trans. Binmed.
Eng., vol. BME-31, pp. 47-52, Jan. 1984.
(71 P . F. Turner. “Electmmsgnctic hyperthermia devices 8nd methods.”
M.S. Ihcsis. M p . Elm. Eng.. Univ. Utah. Salt Lake City. June 1983.
181 -, “Regional hyperthermia with an annular phased amy;’ IEEE
Trans. Biomrd. Eng.. vol. BME-31, pp. 106-114, Ian. 1984.
191 M. I. Hagmann. R. L. Lcvin. and P. F. Tumer, “A comparison of
the annular phased a m y with helical coil applicators for limb and
torso hypenhermia,” IEEE Trans. Biomed. Eng., vol. BME-32. pp.
916-927. Nov. 1985.
[IO] P . F. Turner. ”Hypenhcrmia and inhomogeneous tissue effects using
an annular phased array,” IEEE Tram. Microwave Theory Tech., vol
MTT-32. pp. 874-882, Aug. 1984.
I l l 1 M.I. Hagmann. “Numerical studies of absorption ofelcctmmagnctic
energy by man,” Ph.D. disaenation. Dep. Elec. Eng.. Univ. Utah,
Salt Lake Cily, Dcc. 1978.
I121 M.I. Hagmann. O. P. Gandhi. and C. H . Durncy, ”Numcrical calculation of clectmmngnctic energy deposition for a rcslistic model of
man.’. IEEE Trans. Micrownvr Throry Tech.. vol. MTT-27. pp. 804809, Sept. 1979.
1131 M. I. Hagmann. O. P . Gandhi, I. A . DAndrcs, and 1. Chattcjce.
“ H a d ~ ~ S O I I ~ P CNumerical
C:
solutions and crperimcntnl results,”
IEEE Trans. Microwvc 7ñeory Tech.. vol. MTT-27. pp. 809-813,
sept. 1979.
1141 M. I. Hngmann and O. P. Gandhi. “Numerical calculation of el.%tmmsgnetic energy deposition in man with ground and reflector cffects.” Radio S d . , vol. 14, pp. 23-29, Nov.-Dcc. 1979.
1151 O. P. Gandhi. M. I. H i g m n n . and I. A . D’Andrcs, “Pan-body and
multibody effects on absorption of radio frequency clcctmmgnetic
energy by animals and by models of man:’ Radio Sd.. val. 14, pp.
15-21. Nov.-Dec. 1979.
1161 0. M. Hahn. P . Kernahan, A . Msninez. D. Pounds, S. Primas. T.
Anderson. and 0. Justice, “Some heat transfer problems associated
with heating by ultraround. microwaves or rndiofnquency.” Ann.
N.Y. Acnd. SO.. vol. 335. pp. 327-346, Mar. 1980.
1171 C. C. Johnson and A . W. Guy. “Nonionizing clenmmagnetie wave
effects in biological materials and systems.” Proc. IEEE, vol. M).
pp. 692-718, lune 1972.
118) I. W. Stmhbzhn, B. S. Trembly. and E. B. Douple, “Blood flow
effects on the temperature distributions fmm an invasive rnicmwave
antenna array used in cancer therapy.” IEEE Troni. Biomcd. Eng.,
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1191 I. Mendtcki, E. Friedenthsl, C . Botrtein, R. Paglionc, and F. Sterzsr. ”Microwave applicators for Iwalired hypenhermia trestmenl of
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I201 M. J. Hagmann. O. P.Gandhi. and C. H . Durney. “Upper bound on
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.
41 I
HAGMANN AND LEVIN: ABE.RRANf HEATING
í.2 l .
l 1. W. Stmkhn. .'ThcarctieaI IcmDeratUre distributions for solenoidai-type hypnhermia syrtems."Med. Phyr.. vol. 9. pp. 673-682,
Sept.-Oct. 1982.
".
in%in Medicine and Bioloev Societv forthe Washinston.
DC
and
s . ~.
~.
.
.Northern
. ..~~..
V'&nia chapten and a member o f & Executive Cornminee forthe Warhington. DC chapter of the IEEE.
~ o n n i a LWIO
~.
~~
was born in ~ h i ~ e i p h i PA.
a,
on January 14. 1951. He rcccived the S.B. (wiih
honon) and S.M.degrees in 1973, and the k . D .
Mark J. Hagmno.(S'7S-M'79) was born in
Philadelphi8. PA. on FebNary 14. 1939. He received the B.S. d e g r u in physics fmm Brighnm
Young University, h v o . UT. in I-.
and the
Ph.D. degree in electrical engineering fmm the
Unkenity of Utah. Salt Lake City. in 1978. His
doctoral thesis focused on numerical evaluation of
the absorption of electrnmagneticenergy by man.
Subsequent to receiving his doctorate, he
served as a Research Associate and Research Pmf w r at the Univcnity of Utah. He was a Visiting
h f u r o r in the Department of Electrical Engineering at the University of
Hawaii. Honolulu, fmm 1981-1982. Sincc 1982 h e h u workedasa Senior
Suff Fellow in the Biomedical Engineering and Insmimenution Bmnch of
the Division of Research Services of the National Institotes of Health. Bethud.. MD. His general research interests include numerical pmndures
for electmnugnetics. elcctmmagnetic imaging. biomedical applications of
micmwavrj. and clcctmmagnetic biological effects. Cumntly, he ir in-
in bo<h thCOretical and experimental sNdies regarding elenmmagneüc applicmn for use in hyperthermia.
Dr. Hymann is a member of the Bioclsuomgnctics Society, the Radiation Research Society. and Sigma Xi. He is Chairman of the Engineervolved
degree in 1976. all in mechanical engineering,
from the Massachusetts Institute of Technology.
Cambridge. Hi<dDMnl thesis dealt with the numerical madcling of the water and solum transpon
pmccsses associated with the cryoprescrvation of
biological cells al low mmperaNm.
Subsequent to wxeiving his doctoram. he
served PI a Research Fellow for I LIZ yenn in the
Biophysical Laboratory of Harvard Medical khwl, Boston. He then was
an AssiaUnt h f e u o r for three yean in the Siblcy k b l of Mechanical
and Aemspace Engineeringof Cornell University, Ithipa. NY. Since 1981
he h u b a n LI Biomedical Engineer in the Biomcdiul Engineering d Rem h Branch of the Division of Research Servicwi of the National InstiNIa of Health. Bethe&, M D and an Adjunct AuiMint Fmfesror in the
Department of Biomedic8l Engineering of the Johns Hopkina k h m l of
Medicine, Baltimore, MD.His gcnenl research interests include bibheir
and mass transfer phenomena and p h a r m n ~ ~ k i ~ Cumntly.
tic~.
he is invalved in both hyperthermia and cryobiology research.
Dr. Lcvin is a member of the Fadiation Research Society. the Cvobiology Society, the American Society of Mechanical Engineering. and the
American InstiNte of Chemical Engineering. He h u just completed a tern
as Chumun of the ASME Technical Committee on Bio-Heat and Mass
Transfer.
.
i
I1 I I
-0
TI<\\54CTt(*\5
O \ Hll'\'l
I,I< 4 L 1 \(iI\l
I HI\<.
\ lit
H"I
31
I
J \\l
ANI
Usable Frequencies in Hyperthermia w i t h ( .
Thermal Seeds
WILLIAM 1 ATKINSON. IVAN A BREZOVICH. ANO DEV P. CHAKRABORTY
Abm-Tmperatun
distrlbutions are cornpuled for tluur models ~ M I U I I C
to~he heated by muslnnl p w c r seeds. and from that. the
katlnp power wbkh thc lmphnts have lo produe 10 achkvc clinicdly
acnptahk rcmpcmlum In lhc I u m r u e ohlained. Calculations of
the hear produced by thermal d a exposed Io an ekrtromagnrtk
inducilon liehi showed it lo k drongly dependent on the pcrrneahiiity
o t the m t e r l i l . on th &Id trequency, on Ihc seed di.mcter, md on
tbr orlentition of the implints wiih respect to Ihc Rrld. II ir recommended <bat, o t k p a m e i e r r permltling, the impinb be oriented
puaUel lo lhc id&hi and that the liehi frequency he ippraxlmitely 200 kHi or lower. Under I h m conditions. implants wlth diimcien M rnaü .d 0.25 mm produn iumctent brat for M y clinkcsl
i p p l b t l o n without un$= heiling by eddy currents Rowlng within the
patlent. The uu of frequenck above the mommended
puis
n m i n rrsirktions on the Implanl gcomdry and on the -mtk
p n p r t k i o t their milerial. Nndles orknlul perpendicular io the
Reld produce emugh heat to reach therapeutic iemprraium only
within a n i m w range of parameters.
I
1.~NTRODUCTION
N local hyperthermia, one usually aims at elevating the
temperature of the tumor to a therapeutic level while
leaving the temperature of surrounding tissues essentially
unchanged. Superficial tumors can be heated by a variety of
techniques, e.g., resistive heating with external electrodes
[ I ] , 121, microwaves (31, and ultrasound [4]. Such techniques, however, may pose problems in heatingtumors, the main one being the overheating ofhealthy tissues.
Thus, in certain situations, some invasive method of heating
might be preferred. Invasive methods now under consideration are heating with implanted electrodes [SI -191,implanted
microwave antennas [10]-[13], and thermal seed heating
[141-1
161.
In the last method, the tumor is heated by implanting into
i t ferromagnetic needles (thermal seeds) and by applying an
electromagnetic induction field. The induction field can be
generated by a coil encompassing the tumor-bearing region.
There are huo distinct categories of seeds, namely, constant
temperature seeds and constant power seeds. Constant temperature seeds are made from a material with an abrupt
transition from the ferromagnetic state to a nonferromagnetic
state. They produce significant heating power below the
critical temperature and only little power above it. This
*at
property
implants are at the Same temperature, and thereby some degree Of automatic CQmPenStioti
-,..
for inhomogeneities in the thermal properties of the tissues
is achieved. Various nickel alloys have been suggested f
material of the implants [ 171. [ 181. Constant power
are composed of a material with the critical puint Car
the clinical temperature range, and they iherefiwc p
in a given induction field a constant amount nf pow
gardless of their temperature. A typical material for
seeds is stainless steel W30.
Comparing the temperature patterns obtained by ih
types of thermal seeds, the pattern produced by the
stant temperature 'hpiants can be expected lo be
homogeneous, and thus ir the superior of the two. T
quuements for the material of constant temperature
are, however, very stringent. The needles niusi be
of producing sufficient power to reach the desired
ture, and the transition from the ferromagnetic to
ferromagnetic state should be sharp. Therefore. c
temperature seeds may not become available for lar
clinical trials for wme time. Constant power seeds. o
other hand, can be made of a wide variety of materials.
less steel #430, e.&, can be purchased in the form o
having any desired diameter. We will therefore restric
present investigation to constant power seeds.
For the construction of a thermal seed hypert
system, it is necessary to know what magnetic
the seeds must have and at what frequency and
the electromagnetic induction coil should o
questions are addressed by means of a theoretic
In Section 11, the unavoidable heating by eddy
investigated and shown lo put certain restricti
frequency and intensity of the induction fiel
111, temperalure patterns are computed. and from
heating power which the seeds have to be capable o f p
is determined. Section I V explains which combinat
induction field frequency and magnetic permeability o
implants are able to produce the required power. Secii
summarizes the findings and gives specific recommendaiio
for the optimal range of induction field frequencies.
11.EDDY CURRENT HEATING OF T i s s u ~ ~
wen
the tumor.bearing region is placed into an el
magnetic induction field,
tissues are he;ited by
currents flowing within the tissues, as well as by the th
currents originating from the hot seeds. In this section. ihe
formertype ofheating
be examined,
It
has
been
demonslrated
that for frequencies up io thc
r"
10 MHz
Manuscript rcceivcd March 1.1983:~evi~cd
juty 30, 1983. ~
h
i
~
~
~ region,
~
k there is essentially no attenuation of thc
was mpporicd inpnrt by theComprehensiveCaneer Center Coresupporf magnetic field within cylinders of mus,hequivalenl m i i r ? ¡
Grant CA 1 3 1 4 * a n d a m n t fmm the Friends of Lebanon, Birmingham, having radii
lo or maller than
of tlie ~iuman
l
r
AL.
The authors arc with the Department
Radiation oncology,
uni. [19]. Starling from this reSUlt. i t call bc sliiIU11 by eienientíW
methods that in a cylinder, the rate o f licit production per
versity of Ahbama in Birmingham,Birmingham, A L 35233.
..I
c
0018-9294/84/0100~070%01.00O 1984 IEEE
.nil
T,?I:?)blood te:!ipar)i'i:i a t point ,?('C)
m
y h m e t r x h l W d ;low rate (m'/kg-s)
p
density c' tis+< I kg/m')
ph
density I:: h l w d I k g h ' )
Ct, specific k a t o! h o d (J/kg°C)
K
thermal ciindqctiiity o f blood(W/m.°C)
H', power gctierdted by metabolic processes per unit
tlssue voisme(W,m3).
11%
ahere
J
the 1'
idd
dn
&stance
&e edd,
pmduct
d e r th
pt*nl
Since we will only cunsider cases in which the rate of
yeit produced bq the ihrnooeeds is much larger than the
etabolic, heat pi'uduation rate, we can ndgiect the term on
e righthand
. '
sIdz of (2). in addition, we will assume that
*e temperature (or' the blood as it reache1 any point in the
$s.me voleme will be normal body temprpture (37OC). Thia
*sumpti+
implies that each volume elemmt of tlssue is per%sed by blood ves+$ not connected to neighboring voiume
dements. Equntior. (21 is therefore a betternpproximation for
e
r
spetfused by capillaries than by larga veins and arteries.
us, deftning
x
AT(?) = T(í)- T,(r)
Where now Tb(8= 37'C, (2) becomes
V 2 ( A T )- u2(AT) = O
(3)
whereby
(4)
ip the blood perfusion constant. It is understood that AT =
47x8.
In derlving the sobtion to (3), the r-W wll be trken
darallel to the directbn of the inplanis. If the needier are
long compared tu the cross-sectional dimenlions of the a m y ,
the z.depbndence can he neglected and the biohsat equation
becomes
(5)
The temperature solution to (5) will, be repraented as a
linear su#erposition to N l i e sources coincidiq with the
axes of the neadbs in the array:
u
where r, is the distance between the point of hterest and
meedle i . and K,,is the hyperbolic B e w l function of order
Zero and o f the :scconü kind. By considering the thennoseeds
4s line sources. ni: are neglecting the fact that wme of the
qumor tisue has beeh replaced by metallic implmts. Sinif
rhc. thermdl prcpei:iec *>fthe impianrr .ire very diWerr.nt f r ~ m
@o\r (11 the tissue>, tqw~iilll) in the:: ;a&. ul: h u t iocivci.
tiuns will not be exact. However. the error should be very where
small since in any clinical situation. the total volume of the
implants will be small compared io the tumor volume (les
I< =(
than 5 percent). The expansion coefficients A i in (6) can be
d,,
found from the condition that the power emerging per unit
length of each needle has the same value P. Using Fourier's
r
law of heat conduction, the power emerging from implant
r > = { dfi
i can be represented as
P = -K
t
o ( A T ) . di
(7)
for r < d,,
forr>df,
for r > df,
and I,,, and K , are hyperbolic Bessel functions of the
and second kind and of order m = O, I , 2, -. Noting
1211
where the surface integral is taken along the needle surface
over one unit length of needle. Doing the same procedure
for all needles yields N equations for the N coefficients AI.
To carry out the integral in (7),we assume a cylindrical
and that upon integration over @ all terms
coordinate system with the z-axis coinciding with the axis
cos [m(@ @ti)] will vanish, we gei
of needle i. Writing the gradent operator explicitly and substituting the expression for AT,(7) becomes
-
Substituting(ll)and(l4)
into(8)gives
Q
where ri is the distance from needle j to the point of interest. where i = 1 , 2, '-, N.Upon solving the ensuing set of e
having coordinates r and 9,and u is the radius of each needle. tions for the expansion coefficients A, and substitution of
In our coordinate system,
Ai into (6), the desired expression for ATis obtained.
The power per unit length of needle is shown in F
(9) as a function of the blood perfusion for 3 X 3 , s X 5. a
r
j= [r2 + d j ; - t d l j cos (@ -@#)I
7 needle mays evenly spaced throughout a 4 cm2
where dG 1s the distance between needles i and J and @uis the needle diameter being 1 mm. The blood perfusion
the anguh coordinate of needle j . The dependence of
normalized io that of resting muscle mo = 4.50
on the partiwlar orientation of our coordinate system with IO-' m3/kg-s and the thermal conductivity is fued at thd
respect to ti.^ needle array d o e not lead to any ambiguities for living muscle K = 0.642 W/m."C (231. The h e a t i n g p M
of the results. As we will see later, all terms containing
was computed for a temperature elevation of l*C at a @
drop in the integration over @.
midway between the central needle and the nearest needy
The first integral in (8) can be computed by use of the reia- aiong a diagonal of the implant array. lsotheml plots
tion I2 I]
vealed that the temperature at this point is close to the m i d
mum temperature in the central region of the tumor. The com
a
puted heating power can therefore be considered as the pow¡
Ko(w)=-nK1(~)
(lo) required to elevate the temperature of the coldest point h
ar
the tumor by 1"C.
and by intcgralion over @:
It can be seen from Fig. 1that the power required by the
needles increases with increasing blood flow. In addition.
closely spaced needles require much less power than needks
( I i ) spaced far apart throughout the tunior. The above invesiigb
tions were repeated for needle diameters ranging from 0.1
to 2.0 nun. It was found that the power levels differ at moS
The second integral can be evaluated with the aid of the exby 0.1 percent from those computed for the 1 mm diameter
pression [22]
seeds. Thus, for all practical purposes. the heating power ir
independent of the diameter of the seeds if the minimum
Ko(wij)=Io(m<)Ko(m>) + 2
I,,,@r<)Km
X (w,) tumor temperature is to be elevated by a given amount.
m=1
As an example of the temperature computations, tempenture distributions were obtained for a 4 cm square array of 1
(12) mm diameter needles spaced I and 2 cm apart (Figs. 2 and 3).
COS ím(+ -&)I
x
-
-
,/
-.
CI
/
/'
needles are capable uf producing cnuugli h e l l
range of permeabilities and induction field ire
fact. in some applications. even noní'erroniagn
6 = I ) could be used.
v:h:
'
4-60
-
.
3:
fíhHzi
10'
3x10'
Hating power p r o d u d by uicrmal seeds oriented pmuel to
the induction field. The ppnmacr #~= F a 2 w h m the ridbra is
pressed in millimeters.
F@. 4.
(a)
ItkHZI
.m
Hating Power p r o d u d by thamai rcedr oriented pcrpendic.
u k to the direction of the induction fieid.(=) seed diameter = 1
mm, (b) seed diameter = 2 mm.
Fig. 5.
It can be seen that the heat production is gcneraily much
higher when the needles are parallel to the magnetic field.
In this case, there is a large nnge of frequencies and permeabilities for a giwn seed diameter in which the amount of power
required for adequate tumor heating, computed in Section
111, can be attained. The power drops for both orientations
as the frequency is increased. It can be seen that PI depends
strongly on the value of 8, and therefore upon the permeability for a given needle diameter. The dependence of P, on
the permeability is much weaker than for Pa. Note that
in the perpendicular orientation, 1 mm diameter seeds produce
sufficient power for adequate tumor heating only with a
narrow range of permeability values and only for close (1 cm
or less) needle spacings. On the other hand, 2 mm diameter
V.CONCLUSIONSAND DISCUS~ON
The heating power required by thermal se
quately heat tumors was calculated from a theoretical
Computations also showed that themuseeds can p
sufficient heat over' a wide range of induction field f
cies. The usable frequency range for a given t
was found to depend on its permeability, and since
quired heating power depends on the density of the
arrangement and the rate of blood PerruSion of the
on the particular application as well.
When designing a hyperthermia apparatus, o
in principle, make it operate a l any desired frequenc
magnetic permeability of the implants. on the uth
is rather difficult to control. It therefore seems
induction machine should operate at a frequenc
permit the greatest flexibility in the choice oí jí.
shown that induction field frequencies of about 20
lower would satisfy this condition. In the parallel arra
1rnm diameter needles with jí > 8 would produce
power. Needles with larger permeabilities would b
of producing more power than needed, and th
diameter implants could be used or the magnetic
sity could be reduced below the level assumed in th
tions. A lower induction field intensity would mak
thermia treatment more comfortable since !here wo
less eddy current heating o f the region exposed to the
lion field. This would be especially advantageous in the t
ment of obese patients.
We have shown that needier oriented at right angles
induction field produce substantially less power than
oriented parallel to it. While the perpendicular arrang
may be capable of producing sufficient power to heat t
in certain situations, the margin of extra available
would be generally very slim. It is therefore likely
many situations, the needles would not be a
sufficient heat.
In the computations of the power produce
seeds, the product of the field intensity time
was assumed to be fued at a certain val
lo assure that healthy tissues would n o t be unduly he
by eddy currents flowing within the patient in the case
the chest or the abdomen were exposed to tlie indu
field. In the treatment of tumors of the extremities. Iiowev
the relatively small radii o f the exposed bud) regions and I
resulting decrease in heat generation by cddy currents should
make it possible to use an induction field
value. Therefore, the reduction in the heat g
thermal seeds, which was shown to occur at high field fw
quencies, could be compensated for by 3pp
intensity. Thus, in the treatnieiit <iflesiuns
a wider range oí induction field frequiiicies iuiild be used
than in the treatment of visceral tumors.
Finally, we want to niention that tlie relir
production of the thermal seeds at high ind
REI~ H E N C E S
L r r r n . S. Wapnick. V Picone. G Vaih. m d N. ~Uinicd,
:ndic;uion by rarliiilnequcncy rhcr.<py " J . 4mrr M u d .
235. pp. 25-2''.
11.1) 1976.
.s. "Use of tí ticid\ 1.0pmducc h!pcrrhcmiii i n animiil
in Pioc. lilt. S y n p i:unrcr Ticrop> b:, H)prrihcrtniii ond
ihingim. DC.AUK. 1975. p p 226~227
u n . A. W. Cuy. i:. G . W m x . B. J. lklitcur. and 1 U.
<c. "Eviluation o(. a micmwwo c o r i l i ~ tuppiicicoor."
I. Mrd.. vol. 51. pi!. 143-146. 1970
mor. D.Pounds. 1'. U . Postic. mil<?.M. H;ihn. "7'rcaI.
aiprficial human nrnplmm hy hypcnhrrmia indueill hy
1," Cancer. vol. -I). pp. 1%-XlO. 1979.
1 mdC. V . McClihc. "A tcehniquc for Iocdizzd hcaiing
An adjunct to tumor ihrnpy." Mrtl. Inrtrurn.. WI. 10,
J.ri.-Feb. 1970
tu.J , M. Hcvczi. kl R. Manning. . i d E. J Orimsk.
cry of intersliiial lhcrrnoridioth~rapy." in P r o ' . i d lm
ncrr Th'licrnpy b.y lf>perthermio,Drug.<. ,ind R o d , h t r
O. Junc 1980. pp. 5115-507.
rnning. T. C. Ccw. and E. W.Genier. "inierstiiiil
¡ahcrapy." in P i o í 3rd Ini S y v C a m e , i h r r q ? by
d a . ~ r u . r~i n. d a d . F W ~ C O I I ~co.
~ E JUW
.
IYXO. p p
.
rovieh d I. H. Young. "Hypenbrmia w i t h implanicd
." Mcd. Phyr..
vol, 8.
pp. 79-.84. Jan --Feb,I9H 1
Y. I. A. Brrzouich. W. I. Aikinrm. I>
P.ChiiLribody.
ni. 1. l n g m . and R . 8. Mclilvein. "iiypctthmrnia with
I: in v i m and i n vivo c<,mla~ions." lm. J.
B ~ O Iin
. Piiy.t.. vol. Y. pp. 373-..3112. i ~ 8 ~ .
W.S m h k l i n . E.Bowers. and J Wilrh. "Cancer
nhcnnin using M inrriive rnicniwavc iysteni."
ver. vol. 14. pp.181-186. Jan.
. E.
1979.
Boweri. J~ Walsh. and E ü. Duuple. ,'An
wave lystem for locally-inducd hyperthermia for
1, Mirmwavr Power. vol. 14. pp. 339-.3.50.
.
Fellow at the Compo
Brmingh.tm imm IY
h"iBi,i.aer~Pn,p.. vol.
[SI
1963.
w
vol. L14. rp H72?..H'25,
"Conthou@meamremen: o f utcnc x m . , a ~ : ~ g e dl.'fer!i
enti and VC?, b microcomputer," Am& ,I.PI:)<io:,lol. 245,
pp) H 1 7 8 8 1 S 2 , 983.
[91 G . .A. Mook, O.
ran Asscnddft, and \?.,G. Zljlslrii. ' % w e Icq:th dependenq of the appatmphotom, 't: derentiinitioii iof
b W d oxygen aaliration," Ciirr. Chlm. .4<:u vi I 26, pp. 170179, 1969.
-,
.
Dk*cbic Ptoperties of Süüd Tutioiu D1irin.g
Nombtbemb end Hypertbcmiia
ROE%RTPELOSO;DhVlDT.TVMA, A N D :xAKI~SH
K.. ] A D ,
%bsrdr-D*lcctric
p m : p e u oí five rat munrncy i:ircinomlu,
O n e R t ~ i w n i , ~ r l R t / m ~ r k w c r e m e u u iYai ld
mL;8t37ind43"C
,
over a I)quency
of 1 MHz-I GHE. N6 -4gnlficmt di1Tmrncn
were w~ad
in the ~uisureddielecmc prq<:rlics xtf normal mid
neoplaati: h u e s , praai)mrbly due tn the hi@ ,vat= ccmtunt of luth
types of twirs.
---7
L
lNTRODUCTION
Recem research hps indicated that loo;iiiz?d :.iyper:hei mia
can be induced el'feqtivdy in mrnc tumolS ')) rudío tlcpuency
currents (RF) arid dy microwave power I W V ) a i a m O n i of
cancer t e a t m e n t [i]-[31. Sinci: the theniial energy ahsoiied
by a t i g u e from tin RF/MW source depeml. r.por; its electi ical
propertbs, characterbation of these propc' :irs i)! numml ind
eltecneoplas@c tissues is kmportani fix using ti :SI r~i:th,>d,i
lively [ 4 J . Alth,ougb a number of invcsti@:o.s !),:,veniiasimd
,in)<:I va:.iwui ,101the coqiplex dielccttic constant (e* E'
mal tiss(ies over ii wirte frequency range [5 , [ 6 ] , the '.lui:. on
ncoplas(ic tissues are scant L71-l I O ] . We ' h < : r e ? , ~m::asi.red
re
-
-
Manuwipt rcceimd Ftbruary 16, 1982;revised 'darct~ 7. l!l44, This
work wa) supported bi( a Research Career De% 'p m e 9 A'wd A .id a
NitionaiGcknn Foiindk1wn Grant to R. K.lain.
R Pclojo is with the +piirtmentof BiomediCJ 1:n &m:t rinl:. ( ' a r m :pie
MeUun L'hivarsily.I'iitrairgh. PA 15213.
D. T. Riirna was with tho Department of Eleu c I E r $ini:crmg.1:arne@eMeIon University:Pitirburgh. PA. He is no d c c t a r d .
R. K. hiin is with :hs Delt.irtmen1 of Chemical ni in5 e W I ~ ]',C u w c i e MeUun Chiirrulb. F'ili~Ourgh.PAlS2I3.
!
<l,.I
...
r
i
i
-
i
the dielectric constant 3nd cbnductivity i n i'irro of a variety of
neoplastic tissues from the rdt over a frequency range of I MHz-
1 GHz at 37 and 4 3 T . Frequencies within this range are used
for the heating of tumors [ I I .
EXPERIMENTAL APPROACH
We used, in this study, the shielded open circuit coaxial tine
method developed by Bussey [ 111. The use of an open circuit
h e eliminates the need for accurate determination of aample
length, allows one sample to be measured over a wide frequency
range, and permits instantaneous access to the tissue sample.
The coaxial sample holder (outer cylinder 31.6 mm X 7.0 mm
and center conductor 3.0 mm X 6.3 mm) and its contents were
uniformly heated by a lucite water jacket surrounding the sample holder. The temperatures of the sample holder and the tissue
weremaintnined within * 0 S 0 C o f the desired temperature [ i 21.
The amplitude and phase angle of the reflection coefficient
of the coaxial sample were measured using a General Radio
oscillator (GR 8601A) and a HewlettPackard network analyzer
(HP 8407A) for frequencies helow 110 MHz, and a HewlettPackard oscillator (HP 8690A) and network analyzer (HP 8410)
for frequencies above 110 MHz, in conjunction with a phase
magnitude display unit (HP 8412A) anda transmission test unit
(HP 8740A). These measurements were substituted in the transmission line equation to obtain the dielectric properties ( 111,
[ i 2 1 . The instrument precision in determining E' was 7-10
percent for frequencies less than 50 MHz, and 2-7 percent for
frequencies .greater than SO MHz. .For €".the precision was 1-2
percent for frequencies less than 5 0 MHz, and 2-15 percent for
frequencies greater than 50 MHz. Distilled water was used as
a standard to calibrate the system. Propanol (Table I) and
freshly excised rat muscle tissue (Table 11) were used to cornpare our measurements to the available data 113 1 -[ 15 I . The
spread in the available data was about 15 percent (owing to
different preparations), and our measurements fell in this range.
Dielectric measurements were made on five rat mammary tumors (Walker 2 5 6 , MTW9, MTW9A. NNU, and 13762), one
rat glioma (9L),and rat muscle. AU tumors were grown subcutaneously in rats and were excised seven days post implant.
Average water content of these tumors was approximately
80 percent (Guiiino, personal communication).
Since most of the neoplastic tissues were kept frozen until
the day of measurement, we also investigated the effect of
frozen storage on the dielectric properties of rat muscle. The
difference in dielectric constants o f freshly excised muscle and
previously frozen muscle was found to be less than the experimental error within the frequency range of the study [IZ].
RESULTS
Shown in Fig. 1 are the dielectric properties of six tumors
and rat muscle at 37'C. Temperature coefficients, calculated
as ( E ~ V - e430)lE3p X (i00/6"), are given in Table 111. The
difference among the various tumors in values of E' at 37 and
43OC was within the experimental error, and there was no clear
Qend in the effect of temperature on E' (Table 111). On the
other hand, ail tissues exhibited a temperature coefficient of
about 2 percentl'c except for the highest frequencies (>IO0
MHz) where we have established a large uncertainty. The temperature coefficient for E" is in agreement with the reported
value for normal tissues [ 161.
DISCUSSION
In order to explain and condense the data acquired on tumors,
-. two sets of equations with five parameters were used to fit the
experimental data. The first was the Cole-Cole equation ( 1 4 1 ,
[ 151 and the second was a set of empirical equations. Since
we could not fit the data well t o the Cole-Cole equation ovel
the frequency range 1 MHz-I GHz, we opted, for convenience,
to s t h e data t o the following expressions:
I-
-
18.6.0.6
lo
16.1
lS.7-16.6
23
18.1.1.0
50
18.L.l.C
17.7
17.6-17.8
7s
18.1.1.86
17.7
11.0-18.4
1 w
18.1.2.31
11.1
17.1-17.6
zoo
17.1.3.64
11.3
16.9-17.6
16.8
14.9~10.1
P?oP.nd
zoo
17.0,l.O
400
lb.2.8.S
24%
18.3
17.9-18.6
14.1
14,s-16.3
10.7.8,s
'Oo
8w
11.3
11.3-11.&
7.6.7.1
6.S.b.8
lwo
cOMsA
lo
200,1260
lS
109.S26
161-196
so
91.282
75
80.18s
104
92.llb
19.5
75-83
73.S.152
63-72
56.30
*oo
S3,Sl.S
sz.s.33.s
IW
log E' = a
log E''=
,3.8
s1.54
d
+b
log f
+ e log f
C
+log f
/bW4 3
.. ,
Here, a , b, E , d , and e are empirical constants, and
'
frequency in Hz. The empirical equJiions fit the dala t o b d
than 1 percent, and the Cole-Cole modrltoabout I O F ' $ ;
[121.
L.I 1
..
112
1 26
J 51
1 55
1 18
- 1 11
1 97
1 61
1 91
L 12
-1 27
-1 O0
8.8
.I
.5
.2
.4
.6
i.1 i
.9
.o
.7 I
.2.
1.4
1 O2
'.E1
- 1 81
- 1 01
I 58
1.9
,.o,
8.Z
! I,
F !EOllliNi:Y
:a>
.L.
.o
.91
1 91
L 8s
L I1
1 54
1 57
oi 0
100
IO
IHHiI
.I
.6,
.f
. 91
1
.6'
35
.&
.
i
,
'
94
, 67
! 51
z 28
.28.
.l'
. 43
.5,,
.4:
,.3:
39
'.4.
I1 O0
.or
- 1 80
I
P
'?,S*
I :#¶A
U
A.4
I'
i
l
l(I
I':lll(4
i
I"
" !j
. 'I
'1.)
,
I
Ir,?
I
! . I
! .!
I .I
o 12
a14
o
75
o a?
iE
51
I1
'/I
!1.1
!1.7
-.(I .9
L2.l
-.9'O
!2.7
-.94
-.9.¿
L.
. I L,
r.c
IV are t,he I i e i t S i t p;irain:terI,.alitci I. r ¡ u
iry urcinomas--WZ!i6, MiW9. HTW$ i
hlN!l,
, ~1.1
e rat
It. i r d r a t muscle ;it 8:;l mi! 83
:he values for ,111siii r e o p i a r t i c tinucp a r i ~ l : ,L
those of musc,e. a iiii,hwalcr conicl! riir I.: 5
expected since. witliiii this f r c q u r i c y 1inre I E ;I'IltiLnt ir the o r i m a r v 1,lctor. H o w e w i . k I f ' u 11. !!I
ITable
I.",,,
1 1
Qr P. 14
I
, I
IT.
.
i,
,
UUllii
o,
Cancer I n i t i t u ' e .
I Iiom Qr R. J
i e l i o r r IYu>ptt 11
r
REFERENCES
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n
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tiuues during norma and hyperthermia." MS. th
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S. K.Garg and C. P. Smyth.'Minownvcabwrption
structure in liquids. LXI 1. Thethreedielectricdirpr
of the normal primary alcohols." J. Phys. Chem.. YO.
1294-1301,1965.
K. S. Cole and R. H.Cole, "Dispersion and abmrpti
trics. I. Alternating current characteristio,"l. Chem
9,pp. 341-351,1941.
R. Pethig, Bioelectric and Electronic PropertiesofB
terials. New York: Wiley, 1979.
H. P. Schwan and K. R. Foster. 'RF-field interact'
logical systems: Electrical propertiesand biophysical
Fmc. IEEE.vol.68,pp. Iü4-l13,1980.
T. E. Dudar and R. K. Jain, "Düfmential response of
tumor microcirculation l o hyperthermia." Cirnnr Res.
pp. 605-612.1984.
R. K. lain, F. H. Grantham, and P. M. Gullino, "Blmd
heat transfer in Walker 256 mammary carcinoma."l. Na
hsr.,vol. 6 2 , pp. 927-933, 1979.
..
i ?,
,
,
.’.
A Sufvey of Computer Simulations of
Hypertherm¡a Treatments
i
.
JOHN W. STROHBEHN.
SENIOR MEMBER, IEEE. ANO
i,%,.\, \ , , y ,
Q
-
ROBERT B. ROEMER
Abrirnct-Tbis paper i
ra m k w of lh.
ru<.-o~-lh.-anof a ntw area
of comparative thermal dosimetry is the r.oniparaiiv
in hyperthermia: computerid simulations of hypenhermia ireat.
tion o f ihe abilities o f different Iieatiiig moddiiies
mrnls. OIK of the more dliii.?ult problem in hyprrthcrmh is the
figurations to properly heat clases of tumors. Cal
determinilion of the complete temperature field thraugbout both tufor this application can be done using
mor and nonial tiuue. Thearetical methods of rstimiting temperawhich contain only the most significant milto
ture diitribuüonr are needed lo help address Ibis problem. In Ibis
paper we divide this &Id into four areas: comparative, praspec~ivr, physiological features of “typical” patients and the
concurrent, and mrwpctive. We lhen summirim the malheoutiral
characteristics o f the power deposition patterns.
formulations of both the ekclromagnctic and ultrwnlc power deposifor
prospective thermal dosimetry (individual pat
lion probkms and the beal transfer problem. This is followed by
ment planning) detailed infonnaíion is needed fur
m i e w of lbe numeriul lechulqua available for calculating the power
d e W o n In the tiasve M d then tinding the resulting temperature dar patient’s anatomy and expected blood perfusio
distribution. The paper concluda wüh i
*riplion
of a IC&
ol so that detailed tower deposition patterns can be
i p p l k m k drawn from the current Iiterilurc.
and used to determine a complete temperature d
0.NE of
1.INTRODUCTION
the more difficult problems in clinical hyperthermia
is the determination of the complete temperature field
throughout both tumor and normal tissues.me temperatures
a
areta-s
only a limited number of locations d ~ i n
clinical heating, the temperatures in the +majOutrof the tissue
?e.g& w h o m and it is therefore..difficult .to.a$.gs the
efficacy of the equipment and treatment protocol ut&ed.
Similarly, when planning hyperthermia treatments it is desirable
to be a L k t o . & k u h e temperature fieid to be d=a
in a particular patient so that ihe treatment can be optimized.
To a t i k m i to g y h these
it is possible to use mathe.
matical models of the patient anatomy, thepower deposition
pattern in the heated tisue, the physiological response of the
patient, and the the‘rmal interactions in the tissue to calculate
complete temperature fields in the heated tissues. The purpose
of this paper iS to review the state-of the art in this rapidly
growing field. While analytical methods are appropriate in
same situations, we restrict ourselves tu numerical methods
because they are more appropriate for clinical problems
which normally have irregular boundaries and inhomogeneous
tissue properties.
Computer simulations of hyperthermia treatments have the
potential to become valuable standardized tools in four
aspects of thermal dosimetry [I] : comparative, prospective,
concurrent, and retrospective thermal dosimetry. The goal
for that particular patient. The goal o í these sim
to optimize the proposed thermal treatment by d
the power deposition parameters which niaximize
peutic effects of the tumor temperature disirib
minimizing normal tissue damage and patient stress. Cona
rent thermal dosimetry (feedback control during a treatmg
~involves calculating complete temperature fields d
ment and adjusting PO r deposition paranieiers (and o
variable quantities) to op . ize the actual treatnients as
lined
above.locations
In present
lications,while
measured
coyitrolled,
the goal
at
discrete
are ap
\
treatments is to control the complete teniperat
Retrospective thermal dosimetry (post treatment
of a completed therapy) has as its goal the calc
complete temperature field that was atiain
ment, based on knowledge of the‘measured te
selected locations.. These data are needed for meanin
clinical evaluation of the efficacy of hyperthermia as a tr
ment modality, as well as for evaluation of th
performance and of the heating protocol utilized.
Most hyperthermia related simulation studie
either been generalized parametric investigation
tial of hyperthermia 12) -[I I] or have emphasized the probkrr.
of comparative thermal dosimetry [I?] -1261
one., two-, and occasionally threedimensio
idealized patients, dong with equally simplified power de.
position patterns. Although no work has been reported thr:
attempts to utilize detailed anatomical daia
thermal dosimetry, some work has been repo
Manuscript received June 2 3 , 1983; revised October 13,1983. This deposition patterns alone [27]-[32] iiiclud
work was mpponed in part by the National institutes oiHealth undw
Grants DDS CA 23594. CA 17343, and CA 2 9 6 5 3 , and by the National detailed patient models, and one paper has c;Uc
Science Foundation under Grant ECS 8025818.
ture distributions for detailed anatomies (331
1. W. Strohbehn is with the Thayw School oí Engineering, Dutconcurrent dosimetry, no published work is
mouth College, Hanovcr. NH 03755.
R. B. Roerner is with the Department of Aerospace and Mechanical attempts to control the complete teniperature
Entineering, University of Arizona. Tucson, A L 85721.
to controlling the measured temperatures).
e,
k * wic
u here
where E ir the speed of sound in the tissue. Values h r
may be found in the literature (5 11.
Equation (12) is a scalar version of ( 6 ) for the mr
In homogeneous tissue V*E= O and (5) reduces lo the stand- field. Therefore. !he same general analytical or nu
ard form for the wave equation. i r . , the vector Helmholtz approaches can be applied lo the ultrasouiid prub
equation. However, in patients there are large variations in the EM problem. Since most effort in the ultrasoun
the dielectric constant, e x . , between fat and muscle, and as applied io medicine has been for diagnostic
hence often this term must be retained. When operating at the concentration has been on calculating tlie fields
lower frequencies, ¡.e., in the resistive current range, k’ == ferent sizes and shapes of transducers. Most of 11
iowp. Since we expect significant gradients in E or H over culations have ignored the attenuation in tlie me
. l / R i . factor that is critical in hyperthermia. Finally. a rn
distances of the order of the body radius R,,, if ik3 I 4
then ( 5 ) and ( 6 ) reduce to
ference in applications between the EM problem and t
problem is that in the latter case the impedance mim
V~E:V(V.
E)=O
(8) at interfaces between some tissues, e g . , air-niuscle or
bone, is so large that almost all o f the energy ir refl
V’H = O.
(9) these interfaces. Since significant heating can occur
interfaces (e.g., mode conversion of ultrasound at 1)ie
Note for typical values of Ro (15 cm) and o (0.5 mholm),
this approximation is valid for frequencies up to about 10 bone interface) knowledge of boundary location
especialiy important.
MHz. For this situation we are essentially dealing with Laplace’s
eauation.
The other critical information necessary in solving the
111. NUMERICALM~~~~~
FOR sOLVING
THE B~~~
electromagnetic problem is knowledge of boundary condiTRANSFEREQUATION
tions. Particularly important are interfaces where E changes
‘Ost
realistic hyperthermia problems “quire
abruptly. It is well known that at such boundaries the p a r a e l
solutions,
and fmite differences or finite element
component of the €-field is continuous and the perpendicular
are
the
methods
of choice of most investigators. F
component obeys the relation
ference methods generally require less storage and E
time to run and are easier to program for s
e:EIp = E ; E ] ~ .
(lo)
but data entry for the boundaries of complex g
(7)
Good discussions of the development of the ultrasound
equations from fundamental principles can be found in many
sources, ex., [~i1-[53].AS noted above, the quantity we
need for hyperthemia is the intensity of the ultrasound wave.
As in the electromagnetic case we wu assume $1
are of
he fom p(t) = p,-iwr, ln this fom, the average intensity
at some point is given by
properties
when
finite element methods. At present. the c
method *O utilize depends on the individ
background, interests, and the
Of PI
addition, future developments will perhaps advance
of applicability of both the dkect discrete Fourier
methods [SS] and the weighted residual methods 15
are presently quire fast for problems with 11011
properties and simple regular geometries.
I= IP1’/(22)
(I ’)
For steady-state problems, the elliptic bioheai
=
acoustic
impedance,
equation
is solvable by finite difference methods de
where p E acoustic pressure
equation. For On
basic equations for acoustic or ultrasound waves are nonlinear, for the standard heat
be
lineanzed
sionai
problems,
efficient
tridiagonal
routines are a
but under reasonable appro~mations they
1521. Under these assumptions, a wave equation can be (551. Simüarly, successive over relaxation (SOR)
(point, line, block) are efficient for t\vo.diii,ensiuiiaI pr
written for the pressurePi.e.,
as is the alternating direction implicit (ADl) te
This latter method can be made more effici
V2P + K2P= o
(I2’ i f an optimal set o f cyclic paranteters can be dete
where the complex wavenumber K may be written as
experimentally [%l.
The AD1 method is not 3s exs
tended to three-dimensional problems as are SOR ni
K=k-jol
(13) but splitting methods can be extended to hmriic t l t ~ > ~
lems [ S S I . Most current finite element iiietliiid (FEXi)
and (I ir the attenuation coefficient in the medium. Under niques use triangular elements, stJndard orderins rcilini
most situations of interest in hyperthermia, ¡.e., in media and banded direct matrUr solvers. but tliir is a rapid11 de,
ne
’.o~st“ case
I
I40
.
ITL€ lHANSACTIONS(JN HIOMFDI~~\LINCl?rl:EHI~(..VOL
H X t I 31. NO. i . j A S t ' 4 ~ ~2
'S.!
operating at 27 MHz (741. Once the fields were f m d . they
calculated the temperature distributions using a finite differ-
.,POr
absorbing media, die local intensity can he calculated ,r
cnce method.
~~~o~=Kl*(ro~l*
At this stage in the development of hyperthemid. much of
the numerical analysis is oriented toward increasing our under- where K is a scaling constant and
is the local
standing of system performance (comparative thermal dosim- velocity potential. in this situation. gr(ro) can be
etry), and homogeneous models with regular boundaries from the Rayleigh-Sommerfeld diffraction integral
may be sufficient. In this case, finite difference formulations
are usually quite adequate. As efforts move into activities
*(ro) =
gsk-"" dS
such as treatment planning, where it is desirable to calculate
isotherms for a specific patient, nonhomogeneous
models
must be implemented. In this situation many investigators
which treats the transducer as a collection o f
feel there are strong advantages to finite element formulations
o f spherical waves. in this notation we have
since the basic algorithm is structured to account for both
X
= wavelength. S is the physical aperture of the tr
internal and external irregular boundaries. The use of fmite
and $(so is the aperture (source) weighting funct
element methods for EM problems is relatively recent (771
weakly attenuating media (the acoustic amplitude
(791, and further work in this area is needed.
is attenuated by approximately 1 percent p
The strength of the FEM for clmically oriented problems
of travel) the effects of attenuation are satisfactoril
is that anatomical and tissue complexities are accommodated
by means of the exp (-w') with r' being the path
in a general way in the basic algebraic formulation, such that
tissue
and a the amplitude linear attenuation c
from the user's viewpoint, complex problems are not signifiWithout
attenuation there are several efficient
cantly harder to solve than simple problems. The FEM, in
calculation,
eg., (831; however, the problem is more
conjunction with graphical systems for inputting data, eg.,
if
attenuation
is included. Criffice and Seydel (841pe
from CT scans, and outputting absorbed power and temperathis
integral
numerically
using a twodimensional su
ture data, should lead to systems that can be used in the
over
the
face
of
the
transmitter.
The rapid variation
clinic to facilitate specific patient treatment planning. How.
dkr
phase
term
forces
the
summation
increments to
ever, techniques for preprocessing the data and for automatismall
with
correspondingly
long
computation
times.
cally generating finite difference grids for situations with
et
al.
(as]
and
Swindell
I
8
6
1
have
independently
dev
irregular boundaries are under investigation for the fuiite
method
for
accelerating
these
calculations
by
difference formulation.
The disadvantages of the FEM compared to fmite dif- wards from the point of interest (ro) and summin
ference are: 1)greater complexity in the algorithms and pro- tribution from all points of the transducer fac
gramming, and hence a greater development effort; and equidistant from r,, .
For layered inhomogeneous material, reflection,
2) greater computational overhead. Because computers in
tion,
and mode conversion effects can be included. Re
hospitals tend to be moderate-sized and smaller than those
and
refraction
d o not usually appear to play signi
used in research settings, attention must be paid to developing
in
soft
tissues
because
of the similar acoustic im
efficient algorithms.
velocities
of
most
such tissues. Mode conversion can
in cases where the boundary conditions are known or can
portant at bone surfaces [87].
be approximated with specific values. imolementation of the
~~.
fmite element technique-to the vector EM problem is straightV.SPECIFICAPPLICATIONS
forward in principle. However, the fact that the fields are in
COflhfaDefieDevicm
general complex leads to potentially large matrix storage A.
problems. While there are techniques for handling these
One of the more common regional hyperthermia systm
problems, eg., automatic bandwidth reduction or sparse being evaluated in the clinic is the Magnetrode (Henry Me&
matrix techniques, to date these algorithms are just beginning Electronics, Inc., Los Angeles. CA) (88]-(9i]. which is bir
to be applied to the EM problem as it relates to hyperthermia. cally a circumferential copper electrode centered on the ksi
When the applicator is launching a propagating wave, e%., axis of the patient.
*
y
-
. .
..*'
..
,,..,
.._
*.-
~~
might o
Hill et a
die mon
sorbed F
model. I
die isott
p i d and
et
al. to
,,
t
I
7.5 CM
15 CM
Fig. 2. The finite element grid used for calculating the imthems for the concentric coil heating 1921
IO cm
SKIN SURFACE
5 cm
7.5 em
VISCERA
MODEL: BEST C á S E
15 ern
Fig. 3. A n example of the isotherms calcuhted for concentric coil heating for the case shown in Figs. 1and 2. Viscera
model: skin heldat20'C. blood flowintumor=O;Uivircera,27 mUiOOpm~min;inmurcle-fat 18mViOOgm.min 1921.
c
rn)
Fig. 6.
Onedimensional model for patient PnatomY and tumor used in uniform power deposition airnulition 1151
Recently Lynch, Paulsen. and Strohbehn (unpublished)
approached the EM problem using a fmite element model,
by extending a model o f Lynch [82] for a circulation problem. The basic equation reduces to a scalar wave equation
since in a two-dimensional model it is assumed that the electric
field from the annular phased array is tangential to the long
axis of the patient, and hence there is only one component
E*.Their results look very similar to those found by Iskander
et dusjngthemoment metbod.Theyused the powerdeposition
values in the bioheat transfer equation to solve for the
temperature distributions. The same finite element grid can
be used for the EM and thermal problems. The results are
presently being prepared for publication. More cases need to
be run with these types o f models (using either fuiite element
or moment methods) in order to evaluate how well the model
describes the phased m a y and to answer auestions about
what types o f tumon the annular phased array can heat effectively.
'O-
5)
--Y
45-
$ 402
w.
5
''-
C.Uniform Power Deposition
One interesting question is how effectively would a hyperthermia system that deposits power uniformly in tissue heat
up tumors under various blood flow conditions. Halac et al.
[is] analyzed. a one-dimensional inhomogeneous model of
the abdominal (Fig. 6) and pelvic regions subjected to a
uniform power deposition field. The tissue temperature
distributions were found using an SOR algorithm. Fig. 7
illustrates such a profile for a 7 cm annular tumor model
located in position one. The assumed tumor blood perfusion
pattern had three regions: a highiy perfused periphery where
the perfusion was set equal to the normal tissue perfusion
(W.DR = WN), an intermediate region where perfusion was
one-half of that value (WIR = wN/2), and a necrotic core
with no perfusion (WNC = O). AU normal tissues had the
same value of tumor perfusion (WN). The results of the
analysis are given in a compact format in Fig. 8 for the annular
tumor perfusion model for three tumor sizes (the three columns) and three blood perfusion magnitudes (the three rows).
Within each rectangle results are given for the tumor located
in each o f the five positions indicated in Fig. 6.The results
are given in terms of the range of absorbed power levels
that give acceptable tumor temperature distributions, as indicated by the size of the vertical bars. For absorbed powers
below the value at the bottom of a bar no1 enough power is
absorbed to heat the tumor to therapeutic temperatures. For
Fig. 7.
RADIUS k m l
An example oftempcrawre dirtribution in the unirorm,
depoaition sixnulition [is].
this simulation, the lower acceptable imperatun WIU cl
as 42OC. Conversely. for absrbed powers larger than the
at the lop of a bar, too much power has been applied
either 1)significant portions of the tumor are u n a c q
hot, (this upper allowable temperature was chosen as 6
or 2) a nomal tissue limiting condition was reached. TO!
late clinical conditions, the.temperatures in the nwmal m
and fat tissues were not allowed to exceed 44"C, since a
this temperature there is a risk of tissue dani3ge and
Maximum applied power in such cases is denoted as m
limited (ML) or fat limited (FL). Similarly, since to)
patterns in human whole body hyperthermu suggest that
organs may be damaged if a significant volume o f vi
tissue is heated to temperatures above 4,' C, a limi;
that no more than a 1 cm thick band o f viscera tissue
exceed 42OC was applied (VL). Finally. tile total 1
absorbed by the patient was not allowed to exceed 2 k
sulthg in power limiting (pL) cases. This is a practical
'
"L.-. ................
ux>.
<
0-
r
L
.
.
.
, . ! > I !
VL Y, YL
L. Y L
. . .................
,
. . . :~.!::: ..
<
I l l , 1:111 .I :
,
i
-
'
:4
.
:. ..
I..
.... I..._
T .
I
,
I
.
;
'
F.UU3E-
!
j
i
I
!
,
. ,
. c
[&6]who analyzed a 6 cm diameter by 20 cm lone uniform
tissue region whose axis was the same as that o f the 16 cm
diameter transducer which had a radius of curvature of 20 cm
and was located 10 cm from the skin surface. Figs. 9 and 10
show the SAR pattern and the resulting temperature fields
calculated using an SOR routine for two different blood
perfusion levels and for two different frequencies. In these
computer generated figures, the ten gray levels are evenly
distributed between the highest SAR (or temperature) and the
lowest. The gray levels do not vary monotonically with data
values, but were chosen t o give contrast between adjacent
isotherms. in all figures, ten gray scale levels (10 percent
increments up to the maximum field value) are presented. in
the lower part o f Fig. 9, the SAR distribution for the transducer operating at 0.5 MHz is shown. in the center, the temperature distribution for a blood perfusion rate o f W = 10
kg/m3/s (a value that characterizes viscera) is shown. In the
upper part is the temperature map for W = I kg/m3/s. It is
apparent that the value of W has a profound influence on the
steadystate temperature distribution. The temperature distribution is much more spread out for the lower blood tiow
and although it cannot be determined from the figure, the
maximum excess temperature reached is h o s t exactly
twice that found for the higher blood flow.
Fig. 10 shows the same situation as Fig. 9 except that the
frequency has been raised to 2 MHz. The SAR is seen to be
much more tightly focused, and the steady-state temperature
distributions bear little resemblance to the SAR. in the case
o f low blood flow, a large evenly heated volume is located
within 2-3 cm o f the skin. The temperatures in this region
are approximately the'same as those found at the focus even
though the SAR, as demonstrated by the lower figure, is much
smaller than that at the focus. The existence o f this region o f
superficial heating could limit transducer design and operating
parameters. Scanning will not necessarily remove the superfiiial
hot spot since the superficial heating pattern is quite wide
and significant overlap of power deposition will exist in that
region, but not in the region heated by the tightiy focused
beam in the tumor.
Fik 9. Lowa: absorbed power density due to foaircd US
opcrniiw at 0.5 MHr Middle: temperalure map m high
tissue. Upper: tempmiure map in low pafurion tiuue 186
VI. SUMMARY
The use of the computer to calculate power deposition and
temperature distributions is reasonably recent in hyperthermia,
but the field is now receiving increasing attention. To date
the large majority of the work has been oriented toward
comparative thermal dosimetry, though the techniques required for prospective thennal dosimetry are now appearing
in the literature. Good two-dimensional models for treatment
pia+nning should become commonly available in the next few
years. The areas o f concurrent and retrospective thermal
dosimetry are just in their infancy. Since numerically they
require the same types o f algorithms, they should move forward together. For two- and three-dimensional models we
see no fundamental problems that should preclude algorithm
development.
There are two major problems limiting the progress in this
field. First is the lack o f adequate data to put into the simidations. Clearly, blood flow is the most important physiological
1
Fig.
10.
E
Same as Fig. 9 , except US trmrduccr operating fwqvma '
2.0 hltU 186).
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Amrr.. vol. 70. pp. ISü8-IS17. IV81.
ous
t
.- ..-..
......
i
f
.' $,rript
~
.
m
ri
Ud,
,
I
i
May 30,, 71984.
,, , I,, 112;
, 'wlxd
t:la,rtriwl
~aurcr,E,P,.
,
I
,
cf
currerit.lav&ng 'r.ri!,torv. I'lius. the icnip:it.rure rue would be
well below that i , t otliei ~ I ~ t r ~ ~l hdeey :(lit1
~ . nut consider the
.>.is -3.r
thickness and width, and its electrical and thermal paranirters.
D.c.ni"
.MO .*ni."O
.i.C?&
they calculated the temperature distribution around thc dirpersive electrode and evaluated the effects of these changes on
thermal performance. Due to their use of symmetry in the
two-dimensional model, they could not show the leading and .c,i,,
trailing edge effects.
The main objective o f this paper is lo develop a reasonably
realistic three-dimensional human thigh model that can 1)show
not only the leading edge effect, but also the temperature rise
L.nl
I
5
W
n
e
and fall characteristics with respect to time, 2) explain other
experimentally observed phenomena, and 3) become a tool for
evaluating dispersive electrodes, predicting their performance, Fig. 1. Frontal view of the cylindrical model with 17
levels. Level 1 is the uppermost section of the left th$
and designing better and safer dispersive electrodes.
is the lowest. The x axis points in the lateral directio
axis points in the inferior direction. T h e small interior r
METHODS
rents a full-size square dispersive electrode locatcd be
and IO.
A. A QlindncalModel
Fig. 1shows the frontal view o f our cylindrical human thigh
model. Fig. 2 shows the horizontal view o f our model, one
crow section of the cylinder. The x coordinate points in the
right-to-left direction, the y coordinate points in the superiortoinferior direction, and thez coordinate points in the anteriorto-posterior direction. A s shown in Fig. 1,the model has 18
levels and 17 layers. A level is a two-dimensional cross section
and each level has 242 nodes. Two successive levels form a
slab layer and each layer has 240 hexahedral and prism ele.
ments. The f i t e element method [8] allows us to use different shaped and sized elements to model the boundary smoothly,
whereas the fmite difference method requiresidentical elements
everywhere in the model. A s shown in Fig. 2, we compres the
elements in the top and bottom parts of this cylinder in order
to bring out the details of the voltage distribution and power
dissipations. There are 4356 nodes and 4080 elements in this
model.
To calculate current densities and temperature rises, we must
fist determine the voltage distribution. To fmd the voltage
distribution throughout the model, we solve Laplace's equation:
4
v2v=o.
This equation is subject to the following boundaw conditions:
1) rigid (Dirichlet) boundary condition-voltage values are
specified on the boundary B, ,and
2) natural (Neumann) boundary condition-the voltage
change in the outward normal direction should vanish on the
boundary B2, ¡.e.,
...
whereB, +B2 forms the complete boundary:
In electrosurgery, the rigid boundary condition occurs at
both the active and dispersive electrode sites. Fig. 1alsoshows
one square dispersive electrode located between levels 5 and
10. The voltage value at the active electrode site depends on
the electrosurgical unit used, its operational mode, and its control setting. It is typically several thousand volts. The dispersive electrode is grounded through the electrode cable to the
electrosurgical unit. However, due to the radio frequency signal and high magnitude of current used (up to 1A),inductive
voltage drop occurs along the electrode cable. Thus,,the mlw.
value at the dispersive electrode site keeps changing depend@
on the amount of current collected by it.
The natural boundary condition states that current euuid
enter or leave the model except at the active and dispersive dec.
trodes. However, current can travel in any other direction .)
long as it satisfies the above restriction. Therefore,heat dircip
tion and temperature rise occur not only at the active and dk
persive electrode sites, but also within the boundary and 6
ternal elements.
The human body is so complex that it would be difiicult 10
model it geometrically and physiologically in real detail e K í
with 100 O00 elements. The shapes o f the internal organsad
the outside surface boundary are irregular and complex. Tb
resistivity values and thermal characteristics change from OW
to organ, and from tissue to tissue. Skelctd muscle is hiehi,
anisotropic. At low frequencies, tlic resistivity measured trAn>verse to the muscle fiber direction is higlier tlian that m a d
,
'
II .I ..
.
I
:
!.
s . I I ~< I
I:
.
L
.
'n). tenti&l value after t h e n itera.io IS. :ind k- is the 0ve:rrelo.a ion
is facti) ~hiChsp:edsuptherae,ifo,nvergt:nci:. Without u i i g
~
:ni-
I :
\>'IS
0'1.
o¡.,
-:I?:
I
,i.\",!
1 im I
. ,.
,
.iv,!iiiLiii>
'
.I:.
,
,,.
, .
, I , ,
.
..,
.
,
:
,
. .
,
: I .
I
11'
:We ioptheiterationifanyo'tli:fi>Uowiggconditionsiiri~~:
I ) t& number of itetptions ~xc:eds500,2) the iteratiw E ~ U tion ,!is diverging, or !) changes OF aU nodal voltages bete ein
sum.js$ve itsrations &e lesi thir. a prespeciiied error raiw.
Onl~~hena>nation8)ismet,<io
w e proceed tothenettrtep,
w,wteminpte the nhcle process.
we dietenninekhe vollag< distribution, we calculbte the
density throyh each :lele:nmt using
If "4 move the eleftrode 1o:ation forwatd or backwarcl a .ong
the jy$nder, or if we employ e1ei:t.rodes of different shapes and
size$ the tdal tmoe&nce b:twean the active and diqwsive
elecirades changes, which result3 in different current an4 p , w r
s thniughout the m d u t i i . However, an actual dlectro. set
u*t is able tadeiiver &noit constant power fo@a'vide
in the impe@ance valua. Therefore, the total p w e r
in the whde model n i u t be a constant regarale IS of
inipedanceualue, ¡.e.,
:s .s-
rof
11 d c ! m . : ~ .s ~:ir
~ I n is
iillii.l-:I' VCl.
Power =
1
C I ( ' )vo Y
slf
(81
wht+e;Vol(') is the vplume csf tli,: element i. We use the con.
4 ; ¡:¡. '¡:u. cL,e?!, ient Sta4 total power value o f 105 \V which is the typic4 piwer
> :' +.,>:,I.. i
, r ~.i:-age delibted by an eiectrbsurgical unir with the 50 percent coiitiol
' o :,tbr: v i ' real sett g(h@fpower)?ndpursciitmode [19]-[20].Weailjust
p.,! >., EO PO r'densffies unda differmt conditions to satisfy the conu)) :,! by stad dower ,requirement.
rile
C. hermination of the Teniptrtdure DlsMbution
T) (ietormine the temper2ture distribution. we mwt ,olva
the heat equation
b c
aT * l V a T t P
at
(9)
whse,p, u themarrdensit),,~t : k specific heat.1 the tjhermal
con&mtivlty, and Pthe energy ipteration due to Joulean ieat.
ing.iw@ch has units of power per anit volume. For innct mides,
P isberely the overal power deriiity discussed above.wlulc foz
surtkk nodes expos4d to ra,iiati*mand convection prccr oses.
P ii+lqdes, in addition to thi! p w m density. power lost t i l the
env&qunant due to radiation iind convection. The r d h tivn
le>b!P,hJs . m i t i .tipiwer per un¡! area. It is calculated b y
P, = e,o(r'
(10)
- T:)
where es is the emissivity of human skin (0.97 [Zi]),o is the
Stefan-Boltmann constant 15.67 X IO-' W/(ma . K')], and
T and T. are temperatures in Kelvins of each node and the
environment, respectively. The free convection loss P, has
units of power per uiut area. It is
(11)
P,=k,(T- Te)
where k, is the free convectioncoefficient (23 kcal/fm' .h.K)
[U]) which is equivalent to 2.68 W/(m' .K). We scaleP,P,,
and P, to obtain the total power for each node.
Our model used in determining the temperature distribution
is the same one used in determining the voltage distribution as
shown in Figs. 1 and 2. However. the temperature model is
homogeneous in contrast to the inhomogeneous voltage model.
We use the Same values of the mass density, the specific heat,
and the thermal conductivity for all elements because there are
not any e marked differences in thermal parameters from one
layer to theothers 1121-[14]. Nevertheless,an inhomogeneous
temperature model would be better. We select the massdensity
value pm of 1000 kg/m3, the specific heat c of 3400 J/(kg .K),
and the thermal conductivity I of 0.36 W/(m . K) to model
more accurately the thermal properties of the skin and fat,and
muscle layers that influence most the temperature distribution
around dispersive electrodes [i2].
The heat (Laplacian) equation in Cartesian coordinates is
We can approximate each term on the right side o f (12) in
terms of temperatures of neighboring nodes and distance to
them; for example,
aaT(x,y,z,r)
ax'
-
where the constant a = I/( prn<.)
15 t h C thcrni»nietric
O%.
tivity or the diffusivity. T(x..v.:.f + A l ) is the temperature
Of
the same node after m e A I , and from (13)
and we define ky,,kya,k Z l and
, k Z a siniilarly.
In setting up (14)for every node, we must give s p e ~
Ea.
sideration to surface nodes, because they do not have
neighbors used in (14). in (14). there is only one u
T(x,y , z, I t A t ) . By solving (14)for ail nodes, we
daar.
mine the temoerature distribution after time A l . For thetea
perature distribution after time n A i , we successively detenni
the temperature distribution by solving (14)4356 times,+
ing future temperature values as present temperature vpl
a,
and repeating the whole process 11 times.
When the electrosurgical unit is turned off. the power&%
in the medium becomes zero and heating due to current plas
comes to an end. However, node temperatures continm
change with time due t o conduction. convection, and rada%
effects. If weturn on the electrosurgical unit again before%
around the dispersive electrode cools off and becomes s t a b w
which is often the case during electrosurgery. t h e e i e t m d e ~
even hotter than before due to elevated temperatures from*
previous usage of the electrosurgical unit. Our model sim&
these effects of the electrosurgical unit during the course of^
simulation.
We implemented our model on a T1-990/12time-sharingcomputer and wrote the programs in standard FortranIV [I%
A minimum run time for solving the Laplace and heat tmrufq
equations for a specific electrode and its location in the&
sharing computer environment was IO min. It took 6 s form
iteration in the solution of (3), a simpiifid representation d
a
-.
-
T(x,Y,z,r) T(x - 1 ,Y, 2. f)
T(x + 1.Y, z, r)- T(x,Y,2 . 1 )
Ax I
Axa
A%
where A x , and Axa are distances between the node of our Laplace's equation, using the Gauss-Seidel iterative mnhod
interest and neighbors in the x direction one level above and It took 12 s to dciermine the temperature profde after tlmc
one level below, T(x t l , y , z , r)and T(x - l , y , z , r ) a r e t e m - Ar by solving (14) based on the present temperature dinri
perature value of these neighbors, T ( x , y , z , r )is the tempera- bution. We used a At of 6 s.
ture value of the node of our interest, and xo is the average of
Axl and A x 2 .
D. Experimenral Setup
Therefore, for each node we can represent (9)as
Fig. 3 shows the experimental arrangement used on humu
subjects. The subject controlled the activation and deactivati3
T ( x , y , z , t + A r )= T ( x , y . z . t )
of the electrosurgical unit by a foot switch to avoid possol
+ A r . a { k x l [ T ( x tl,y,z,t)
bums during experiments. Since we wereinierested in thetan
perature distribution only around the dispersive e1ectrode.n
- T(x.~.z,f)I
used a second dispersive electrode as an active electrodt
+ k,l [T(x - 1, Y , z , 1) - T ( x , ~ , z , t ) l
supply RF current through the body to the test dispersive elc.
+ k y l[ T ( x , y + I , z , t ) - T ( x , y , z , r ) l trode. Due to limited skin temperature change, we nieawc.
temperature with eight 34-gauge epoxy-coated copper-coo
+kyz t T ( x , y - I , z ,f ) - T ( x . Y . z . ~ ) I
stantan thermocouples. Each thermocouple could monfio
+ k r i [ T ( x , Y , zt 1.1) - T ( ~ , y , z , t ) ] the time-varying temperature chmgc of a specific point U&
the dispersive electrode without removing the dispersive cki
+ kr2 [T(x,Y,z 1.1)
T ( ~ , Y2 ,,r ) l }
trode. However, it was quite diíficult to get spatial t e m p
t-.
Ar
(14) ture rise information under the dispersive electrode usingtk
PmC
mocouples. Thermography could overcome this problem 12I:
.
.
/ I :,
.
.. . .. .,
111
,..,,::
3
..
~ _ . 1
I
/r
___*
_*
----
*_
_*
-7
.____
-..--- .-_
c.__
(h
I kg. 4. (,L)
Calwlated current Uur sil es across lhe righthalfaf die square
vn in Fig. I and the adjacunl surface
for three
hyyars.
irt cli
pointed by the x and Y. axes u c
mity valiics are tiorrnslirci to the
lpwest curra$ density undd Llie lispcrsive ,:la:trodc. n
i
.
lop curve
tlectrode with a contact qrxi 01' 130 cm:' was located between
levels 5 and 10. It a i n t ~ i i r : dfive layers tind consismi of 84
iiodes and 65 elementi. #:
the
i sinulaticm progressed. we used
.lifferent locations for act$ie and dispersrve eleqtrode!:,;ind d i f
ikrent electrode areas and :;t.apes, 'Pig. ,1 shows the i:ílculatcd
dirrent density across the. iighi half of t.he dispersive uiectrode
.iad the adjacent surface, :irid the temperature rise around it
which exceeds the normalskin temperature of31"C. The cur.
lent density across the lefi hail is symmetrical to that of the
light half. The rnaximuth traiisi'erse current density ratio oí
2.00 across the disperrivei8:li:ct .ode occiirs at the second layer
,if the disperbive electrode [.hf ratio betwcen Ghe current den.dies when r/r = 1.0 and x/r = O along the middle curve in
Fig. 4(r)]. l ñ e rnaximunr ratio betwecn the higheat current
density [upptr left and right cr'rners, when1 x/r = 10 along the
iop curve in Fig. 4(a)l a& r:hc lowest current density [center
of the fourtb layer. w h e ~.x/r = O along the bottom wrve in
Fig. 4(a)] wlthm the dispersive electrode is 3.14. Overmyer
o/. (41 calculated 3 ratio o f 2.9 for the circular electrode
without allowing diflerei't la) err, which is reasonably close
T O our result of 3.14 arid 2,110. However. they did no7 consider
.he leading edge effect.
Our result also indicates; i h a f 1:liere is a maximuri current
:lcnriry ritio of 2.12 ilonl: t h ! dispcrsi.ve ekcirude iii the y
d i r e a i o n , the miiu betwecii r h . i u r r c n : d.~ri~:!!, uf t i e <enter
oí the leading edge [the first layer, when xJr = O alorig thc top
.y '*
curve in Fig. 4(a)] and that of the ínurth layer [when xJr = O
p
.
tribution
along the characteristic
bottom curve at
in the
Fig. dispersive
4(a)]. Theelectrode
current density
shows that
disthe peripheral region withonly 26percent ofthe total dispersive
electrode area collects 45 percent of the total current,while the
remaining 7 4 percent of the area collects 55 percent of the
current. Therefore, nonuniform temperature rise occurs under
the dispersive electrode. Fig. 4(b)clearly shows that the leading
edge and side area exhibit higher temperature elevation than the
trailing edge and center area. The highest temperature gradient
occurs at the leading edge corners, and there are also temperature rises away from the dispersive electrode site. The ratio
between the hnhest
and lowest temperature rises under the
dispersive electrode is 5.52 compared t o that of 4.00 obtained
by Overmyer et al. [4].
B. lime-Dependent Temperature Distribution
Fig. 5 shows the temperature rire characteristics from our
simulations and temperature cooling characteristics from both
simulations and measurements from a male subject whose measured data points best match those from simulations. Variations
in the maximum temperature rises among seven subjects were
+ l " C for the full-size electrode and t3'C for the small-size
electrode. Female subjects consistently exhibited higher temperature rises. Fig. 5(a) shows results for the fullsize oval
electrode and Fig. 5(b) shows results for the small-size square
electrode. In experiments, we used Johnson and Johnson ovalshaped electrodes with 130 cma area for the full-sizeelectrode,
and we cut this full-sire electrode into a 6 X 6 cm square electrode around the dispersive electrode's connector to determine
the details o f the temperature rise and fall characteristics. While
the electrosurgical unit was on, the temperature rise with respect to time was almost linear. Howeve1,the slope of temperature rise tapered off due to effects of radiation, conduction,
convection, blood perfusion, and blood circulation as temperature under the dispersive electrode increased. Using the fullsize oval electrode, the temperature rises after 0.7 A of RF
current for 1min were 2.47'C from simulation and 2.4"Cfrom
measurement, and temperatures after 2 min of cooling were
3225°C from simulation and 32.15"C from measurement. It
took more than 20 min for the temperature under the dispersive
electrode to return to normal skin temperature (31°C). Temperature rises after 1min using the small-size square electrode
were 39.65"C from simulation and 40°C from measurement,
and temperatures after 2 min of cooling were 34.52'C from
simulation and 3 5 9 C from measurement. At this p i n t , we
applied another 0.7 A of RF current for the next 1min, which
resulted in maximal temperatures of 42.36-C from simulation
and 4 1 3 ° C from measurement. If we allowed 2 min more for
cooling, the simulation predicted a temperature of 36.38"C
while the measured temperature value was 36.7"C. These re.
sults indicated that our model could be a useful tool in predicting temperature rise and fall characteristics under various
conditions.
We also modeled a 130 cm' full-sized figure-eight.shaped
electrode. Fig. 6 shows isothermal contour maps after 1min
of current for an oval electrode and a figure-eight-shaped elec-
1
p
,
....,
-
r
3%
O w 1
orr
Tm.,
mm
(81
D
(b)
4
w.
Fig. 5 . Temperature rise and cooling characteristics. Solid h
i
simulation, X indicates meawremcnl. (a) T;ullYze owl
(b) SmiUlizc quare elccuode.
,"?.
6. Iwithnmal contour map showing the tcmperature rise from w
mal skin 1cmPerature of 31'C after 1 min of RF cunent lor (11 b
full-rize ovd- electrode, and (b) Ihc lull-sue fwurc-cwhiJuld
Fig.
electrode.
e.
trode. The maximum temperature rises for these e l e c t r d
were lower than that of the square electrode. The areas wilhp
33OC isothermal contours (2°C above the skin teinpernturc'
decreased, and less than 40 percent of the total electrode im
had a temperature riseof 1"Cormore. In F i g . ó ( b ) . t h e r e d
leading edge at the center ofa figure-eight-shaped electrode
a lower temperature rise than other iionrecessed leading d P
Fig. 7 shows three isothermal contour maps after 1 mb P!
heating, 1min of heating and 2 n l i n of cooling. 2nd I min.'
heating, 2 min of cooling, and 1 ,nit] of Iicntinp. again.
.,.
::
Wr:
Wc
'
WllJ
i
thy
1)i
F
(C)
8, Inoüiermal coqlour map for the sniaiisize oval electlode after
min of heaüngi
1mirl of ,waling and 2 min of c+m.nwi
(4) I min of heating.2 min 01'ciinliig. md 1 min ofadúiiiorüheatii.
m)
thp dispersive electrode depcnds not only on the h@hest temp$"ire,
but alto On the rhcrmal characteristics of underlying
ti** and the dispersive electro(e applied, and the dqration of
tq14which this elevated temper&ture is maintained. Webelieve
t*t;l:he burn temfleraturc for the permanent tissue damage in
t# (high ,area is over 48°C. Th$correspondswell t o m e results
odShahaiíd Webster [3] and PeQiee [ S I .
C; 4ffectt of t h e b c a t w n of Dlsperuvr
oddilctiVe Eiecmdes
!Fig. 10 shows the effect of inoving the square dispersive
electrode along thd y axis in our model. The activeelectrode
l*ion
%Itillfilledithe entire IWd 1and the square electrode
ofcqpied 6 levels. We coiild nqt place the dispersimelectrode
s@r(ing at level I &e to the codflict between the twodifferent
qrkhlet boundaw conditions. When the electrode v a s placed
smrting at level i f , its tiaiiingi edge touched the end o f our
&dci. which has 18 levels. When the dispersive elearode war
l@<ic;ltedI<IOclose 10 the active electrode.the temperature under
¡I;hrc3iii~.quite hy?h d u e to the coiicentrired cunehr density
f
/-
Sloltlnp Lnil
Fig. 10. HQhert temperature under the dispersive elccirodc
tion of its loution in the cylinder.
I,,
Fig. 11. Isothermal contour map for the íull-size square electrode Y
it was placed starting at level 13.
(d
Fig. 9. lsothumal contour map ior the small&e figure-eighthped
elcsirode aftex (a) 1 min of heating, (b) 1 mm of heating and 2 min
of cooling, and (c) 1 m m of heating, 1 min of waling, and 1 min of
additional hating.
at the leading edge and heat conduction from the active electrode site with its very high temperature. As soon as thehighest
temperature hit its minimum when the dispersive electrode was
placed starting at levels 3 and 4, it started to rise as the electrode moved farther away from the active electrode. W e can
explain this effect in terms of imposed boundary conditions
on our model. The model had finite extent. The electric field
distribution which determined the current density was disturbed because the Neumann boundary condition required that
no current exit through level 1 8 in the y direction, however,
the dispersive electrode had to collect the same amount of current no matter where it was located.
Fig. 11shows the isothermal contour map when the electrode
was placed between levels 13 and 18. Due t o the Neumann
boundary condition at the entire level 18, current was concentrated more at the leading edge. Therefore,the temperature
rise at the leading edge was higher than that with normal dispersive electrode location (between levels 5 and 10). At the
same time, the current density at the trailing edge was smaller,
resulting in lower temperature rise at the trailing edge. Compared to Fig. 4(b), Fig. 1 1 shows more concentrated current
density at the leading edge, higher temperature elevation
higher temperature gradient in the y direction. We con
this unexpected result an artifact because of our mo
extent. However, human limbs also have finite di
Our experiments yielded higher temperature rises and
leading edge effects when we placed the dispersive elear
on the lower leg or on the lower ann. iherefore, as long I
dispersive electrode was placed reasonably far away from
active electrode but not close io the end of the extremi
temperature rise was minimal and the exact dispersive el
location became a factor o f little importance.
To test the validity of our active electrode assumpt
changed the active electrode from the entire level 1to
nodes in level 3 in order to simulate the sharp active el
used in electrosurgery. Calculated temperature around
electrode area was several thousand degreesCe1sius.w
be enough to make tissue around it evaporate. Fig.
the temperature distribution around the dispersive electrodr
which was placed between levels 13 and 18. If we e x a d
both Figs. 1 1 and 12 closely, there is no significant differem<.
which supports our modeling of the active electrode,
Up until now. calculated current densities and ternperalui:
distribution characteristicshavebeensyniiiietric iii thex mrd;
nate due to symmetric or centered active electrode locatiom
If the active electrode location is skewed with respect lo tk
dispersive electrode. which is often the case iii our experinimt’
and actual electrosurgery, the teniperature rise oí the two si*’
of the electrode will be different. Fig. 13 sliows the ¡sothem.*contour map around the dispcrsive elrctriide loc;ited bctum
I
'I
*
Icro1:
.
..........
.
l'al : l ~ :I
..
7.'
...........
~
,'.l,:xim,.m
tkrqer:,we
...........
....
l,r
.IS.
...
.....
ziii.:
Sari.* *IIciroi:*
....
Fcpir. Wt1-rtmio.c
awtioa.
-,
squaw .l.Elll<(i I
unibtord
I I(
">Z
Y
",2
2.:":
Y
",Z
I.!'*C
IY
"J
1IL.C
Zi
nz
.-
:.~.í
OM1 *bstW*
/
L Y I I l t dCSi.,
Rinp ibclmd.
~
lar ri1g were ideptical. lii O L I s i x AaticDx WI
vtri:i:
current qensity iiiideii :.he C.spersiw el
i&cd that curreht density tn :very eleincni 1 1 1
to iii.Le the currbnt density unier tke dispmi ,J elbctrijdeuniíottii However,, we cc~uldnqt reniiwe r i h t i v : ! ! , Ygh :went
. . . .......
..... .deiisi'.yat the IeaPingedge outbide th- dispersiv: eledtro' e. The
........
mixiinurn tempaature rise fdi the q u a r e i:!e:iiode w i t h unihi current density wiis I:l7'C. 'Ilús ternpei; lure lis':isonly
....
Wi' or' that of the quare sl+:trode wiLlico1 i.rifdrm :urrent
...........
Liaisiry. I f the leading edge Sfect outside thr dispers;veelec.
xr?dc were removed with the iddition rifaz.withd miieq the
..........
tetnp,:rature rise would have become even I~,wiv.
&i.>rher conceptually superior disperiivc el?cmde !; a ring
alictiode. We b o w thar reaiperaiure r i m < I any di.-pasive
iel4Ct;ode are highest at and ap.>undthe leading t:d$e,a:id only
ia crindi electrode area near 'the luding cdg: Ipanici,latcs in
c<llie,:ting the b d k of t.he ret&rningcurrent I t:;teed c'f trying
tqi:liniinate the leading edge Bifect;xecariIcn!tlientht
leading
e&i: and shortep its uiidih in the v. directioi, tci rediice the
i : I I'UI ; L ; ~w ~ a i : cii:tI ,de
:lebiii,ig edge effect. We raiodeled the ring elerr:ode uith a 21 < ! II, .F a x i r e * tend-location cifi-nidehand encircling the 1'3.cni-radiuis,cyliiisier at 'ayer 1 ,
'retiui:.ing in a 1as.7 crn' cobtact area arid a o;!.& cm leading
,e&
The maximum temperature rise after 1 -.in of O ?-ARF
i,!
,)i:illi
in
.,a.,skeyed
jcjricnt
was only 1.14"C. men we modtled tie ,hay active
,!,:
i
iqer.
.elt:st:ode
in level 3 instead of the eiitirc leiiel J ,t k m simum
~ ! , ! ~1 !$,,ewi
l l,,!>
I,,
I
/
13. la
,
"
,
:
,
,
elec.
tqiilerature r i w o f the! ririg ekctrode at I;iye~13 was 137°C.
'
I
,
'imi :xn jeratii e ['se. for tar-
I , i.!~rhc.iiiispc!rsl!c <b:ctmd.es.
, ! '(i11I :!ii:wic i;!,e, , i f :he cbm, I '01 e ' , Y hile 1 he .rltiare eleci
I i I ¡!;e
H:I NCVCI thdJference
I
'
I:, :(!:I tlian 1,ü iei.iirit. Wlley
, I I: I I c i > d i :'L Iiic t i i, iiivitled
I
,
:,
,
:
I
i
~
:'
I
!,ti[ I t e t i : ¡I(:[
y ' < i t , , e an1 ri: Lit )I values
i i i , : i i ' i i i ~ . 1.h: ,e er. they
! , : 1 , I S I K I I ! ' ~' I, l
i
i
itrly far
, ' 11 ! ) i i i i i ctry; :h; I! ,,cur(ent
I L'c !,'s i
t t h t i i 11: ' J iie.iiiiiii-
I
,I
I
'iI
,
,
iii~:~:t:dto:the
Tb,:r.:fore, we conclude that lby leiigthewig the &ad.ng edge
dktmce in desigbing the <Iispeisive electr(i.de, r'tiichu1 nnntely
letids to a ringelectrode, we should he able to 1e:rdase fhetemp$i;iiure rises sipificantly , and consequently. redlice the risk
olpcssible burns.
Tmle It show6 the maximum tt:mperature rises of square,
ov;il. and figure-~ight-slhap,:dtlectrcideswitha: 6 cmr vectrode
; a h after 1rnin with the rlectrosur?icalunit c 11, 2 min off,and
1.rwn on again.,in sequence. The small S ~ U Í I : elpctr.xle had
"t8e highest teniperature rises. while IIII: .ii."ie..tigh..shaped
ekcrwde had tHe lowest temperature ris,i:i. 'Wtien we applied
a0.7-ARF current for I iriin to thr s q u w rlirlicrrive e cctrode
r r.he first time, thte niaxiiiium temp<:i:iir;iewas :9.6SoC.
miparing Tablus I and I i , the singk mw;r iiinix~rt;~t
fxtar for
the 'emperaturn rise in the dispersive elecIriJ,.li: was .he elect w h ' s area. which is ittie traditional puiiir 01' view. lquition
(1),,Iiowi that the power dem<.ityi r pro~ioiricii;iIto t h J squue
< J I !,liecurrent density Equation 1 9 )s h i w , !.:it the iurnpcritu:.: . t u n g is linc.>rl> rel:itr.J t o i t i i p(wicr d::i,;ii) i i i w e v e r .
. .
<!
Fguia . i g M - W l
6ü2.C
L.931:
I*Et.Cd.
''-
I
"
-
in Table 11,we reduced the electrode's area by a factor o f 3.61
from 130 cm' to 36 Em2. The maximumtemperaturerise ratio
is 3.23 (8.65/2.68) instead of the expected ratio of 13.03
(3.612). This discrepancy exists because human tissue conducts heat quickly t o the immediately surrounding area, and
there are effects of convection, radiation, blood circulation,
and others.
When we applied this current again after allowing 2 min of
cooling, the maximum temperature was 4236°C. This clearly
indicates that factors in evaluating this dispersive electrode
must include time or history of current application, and the
ability for the dispersive electrode to dissipate heat quickly.
The only standard existing to guide in designing the dispersive electrode is the suggestion made by the National Fire Protection Association that 1cml of electrode area is required
for each 1.5 W of applied RF power [24]. In this guideline,
both the actual temperature rise under the dispersive electrode
and the duration of the electroiurgical unit's activation are neglected. Our full-size electrodes have 0.81 W/cm2, which is well
below the suggested maximum power density of 15 W/cm2,
and mallsize electrodes have 2.92 W/cm2. However, i f we use
the full-size electrode and turn on the electrosurgical unit for
more than IO min, the maximum temperature can be dangerously high, even though the full-size electrode satisfies the power
density requirement. On the other hand, for less than 30 s of
RF power application, the small-size electrode does not pose
any hazard even with its unsatisfactory power density.
A more relevant standard might include the following
factors.
I ) The maximum temperature under the dispersive electrode
applied on a fixed location o f a surrogate medium in a controlled
environment, after applying constant RF current for constant
time through a fixed active electrode, should not exceed a prespecified maximum regardless of the electrode's shape,size,and
whether it is gelled or dry.
2) After another constant time of cooling o f f , the maximum
temperature should be lower than another prespecified
tempeiature.
3) After applying RF power again for yet another constant
time, the maximum temperature should be lower than the third
prespecified temperature.
Requirements 2) and 3)could be combined into one standard.
For pediatric dispersive electrodes, a similar set of standards
could be written due to the smaller amount of RF current and
power used in pediatric operations.
Our experimental results have been based on using a dry
dispersive electrode which has only a thin layer o f conductive
and adhesive polymer. However, there is no major difference
in temperature characteristics between dry and gelled electrodes, so we can apply the above analyses also t o gelled dis-
R.IoIoIM Fwior
Fig,
The
number of
.
range and the rclpxation factor usad in
with bounduy conditions. Initial guess
except those with the Dirichiet bounduy
voltage values at the active and dispersive c
o v,respectively. x indicates R I O ~ rangc O
error range of 0.01 V,and q u a r e indicates c
persive electrodes. One difference is that the skin te
drops from 1t o 2°C when we apply the gelled electro
skin because the gel in the electrode has cooled to r
perature. After the gel and skin temperatures have w
due to the applied power dissipation, the rate of coo
somewhat lower than that of the dry electrode because
gel's added heat capacity to the electrode.
For solving Laplace's equation, Fig. 14 shows the r
number of iterations as functions of the error range a
relaxation factor used. We start all node voltage values
those with the Dirichlet boundary condition with the
guess of 50 V. If we use the underrelaxation techni
this Gauss-Seidel iterative method,the rate of converge
down, whereas the overrelaxation technique speeds u
of convergence. The purpose of overrelaxation is to ac
convergence, rather than to promote convergence in an
wise divergent iteration scheme. The use of too large an
relaxation factfr b e a t e r than 1.9) causes divergence.
minimum numbers of necessary iterations are 35, 55,
when the relaxation factor is 1.8 for the error ranges O.
and OaOl V,respectively. We used the error range of 0.001
throughout our simulation to achieve high accuracy in the
tion. With an error range of 0.0001 V. we could not ac
any completely converged solution within 500 iterations R
gardleu of the relaxation-(actor value. The ratio between t
required number of iterations without the relaxation techniq
employed (relaxation factor of 1.O), and 11131 with an o p t i d
reiaxation factor, was 6 3 when the error range was 0.001 v.
Therefore, findinga best relaxation factor is iiiiportant for uivinl
computer time in any iterative problem solving. Also,thenunl.
ber of iterations is a function of the elcctrode 1ocaiion.shap.
area, and initial guess, but in a less dramatic way.
There are some limitations in our iiiodeI3nd ntodelinp tech.
niques that can be improved in future rcx3rch. The effccl @f
blood circulation is not considered in wlvinp the heat transftr
equation (9) because blood carries auay little iif thc heat pew
rated during the I-min test. 1nteriaceshctwcr.n the skinandil'
layer and the muscle layer and betweir the iiiuscle layer 2nd
the femur are not smooth. Therefore, their shapes are not r4urate compared t o the cross sectional picture of the thigh 1151.
~ c t i L T: E W I ' ~ l ~ . . ~ , T U' P, II/
'
!
I~
i l l IN .\ROLIN<> 1.1-
:
,,)r~iiiatc s!stcii. ' l i r o ~ g
I ,'.:,udirjtc tcinsion
id of uún3 I :IC ( 3rteij: KIII: . rciiiilt: s);tciri F
16 problem '111,: ;tiarbcs (11 o v i l atid fipis.e.eig1
&a
used i n Fip. 6,8,a m ! :ir( iiilt p ~ r edy
, ~ ~ l ~ t r o d e si odthe
i i ~ iriite vkiiient ii:itureo
:htiique. 1lic:e 3i c nosliiir~:~c~:rricrriiialirirnc.r
31iJ ti~ure.r.i~:tic-alr.ip~~d
rlwt :ode:i. 'lliereft
~ q r r a t i u edistribu:.ions e:ipr.,:hilly those of 1115. \ ~ i c c 9,
have siqniiLii 11 aitiiac: diie to tile p:eserict o: $ ! i ~ r pcr.
in small arca:;. I f we roriotetl tlihi error in r i)i:d
trodes, the iwxiiiiuin iei7ipc"atiire rises for tl cs: d:;;i~n;dzi
mirized in TaSI: I1 woiilil h.iv: been lower. \Ve . < ! i i < L ) r t .
e this problein tNy criip!oying triangular el4m 111, OII til-:.
aceand usingmxe c1eni~:ntjirittieniodel. q o 1x1:iiriexic
d
e
r inwlving dimensuns of the model, resis i v I I , w (ir..
at
L
D
L
c
I
I , . ' '
ut layeis, and thi,ir theirnd chiractrristics copld Ik.id :c :it1
lanation of wh). individid .differences in t h l tmcer:i[urc
ributions around the dislmsin: electrodesexht, !io.': signil..
mt it is. and how to predict it
-. Phpdmi T.:din;)u~?s
Bu,lc,gi'dReseurch:ck~Vol. 6,W. L. N a m k ,
19 3.
121 J. A. J. SioIwi!L :mi1 I. I ) ~11 dy, "Temperature rcwlatiin in
mai-.A thiore.jc.it SIL:^) ." t' u g m Archir., vol. 291. pp. 129162, 1966.
; ,I. C o b and Y:Houd~~,"Er~iprimentdderemilialion of cwífii(11
Ed. Newiork:Acad:mi,.
CIIKLIISIONS
i
k
We constructed a three-diniensiondc y l i d r ca' cjrirpiter
el of the thigh ibiised i.mthe finite element n etliti.1 to si)Iva
the current density (clisiribution and tern r a ' w ~prc,fili:
mund diapersive ele,:trod.es, Our model is versa1 le .iilri
[Iruiblir
M.Woods, "Thmry.meaiunthat we can easi..y simiilate the sizeof the cy,inii:r, a n J the
, shapes. and locations of different active p i c!is?CriiVi:
rodci. In spiti: of it!, Iiniitations,it isa usefiil !s,,>iY i >re.
k t i g current den:;it:ies and temperature rises arciiir
1: 61 Y. Kim. W. I. Tiripkins,i i i d li G. Webrter, "Athrce-dhnensbd
trades. We coinpared tkie results from our F~I.I:J~IOII; ti:#
rimentd resuiis not oriiy for the rnaximuiii !cni)JcrJ urtl
but also for tooling. characteristics with rJrp:¿: :o tinic.
sirnulitions shuwed tlia!. tho current densityldibt riktiticn i!r
uniform transversely. It is dso nonuniform Jorgircdiii;iliy,
Fronriers Cornput. Med., vol. 1,
lhich is called the leading tdgs effect. Electrobe scimetiy :!I
elactor in determining ithe maxiniurn temp rature ris: i r i
shaped elec:tro'de. The s q w e ele .tr(ide Ius the
est temperiiuie rise, whila oval and figuh.-i~~ylit-slibpe<l .... *,
have sinilar temi:ierature rises. The i o c h m of tho I ! I D. O. Coomy. Iliornedicil Cbgineering Rincipleu. New I'ork
Marcsl I)ekker, 1976.
ive elec~rod: is not inil?ortant as long iis !I 15 pi;tcetl
i:!
J.@
A.
]Pcarcs,
proposcrl inelhod for quantitative pdorniance
far away from the active electrode aid riot close to
evaluation of eldc:rosuruic.il düpcrsive electrcdes.".Med.Inshn<nwil..
vol~13.pp.52- 4 1979
the extri:mitie!i. 'The unportant facto/sin evliuating
[::!DI H.N. N o r t i i n , I b i ; d ~ ~ ! k ~ , T * n r d u c s r ,EkcIrodcMeomrlmg
~
ive electiodeart: the electrode size, tlieiclcr tr<wrgii:al
Synemr. I:ngl&nod C1if.s. NI: PienticeHall. 1969.
I activation time, at:d the electrode's abil$y tv t l i s s i : > m
The ,%fe llse of Hipti-Frequ+cy Equipment in Hospital., wl.
76C, National Fir: Protection Arsuciation. Boston, MA. 1971.
und it. Wi:prop.iscsd fwtors that mightlbe :nc!iiúcd i n
%"
k
1
It1
k9,
e
t.
.. . .
"4
[::!hi
rd for evaliuiing tiis,per:iiveelectrodes. )ie a I ; c qu:!nti.
y examined .I disparsive i:l<:ctrode with uliiftorin current
and a ring elec~ri:,dowith a long leadin4rcig.e. I f 1,lt:se
es were rn,ide aviiihble commercially. !hey !;liould re.
ower teiiip:raturt: ri,ses,and thus reduct$tli,: kizarii of
t
e burns iiiidi!r the ~.lisperr,ive
electrode. W a:Imdiuwsed
cal aspects i'fouriii«~drl:indtheeffrctof he ~iver.reI~~:ci'
'
':
hnique in rubstant idly ri:ducingoveraIl cdinl.Mmgtiine.
Yonlpnin Kim ( S ' 7 9 4 ' 8 2 ) was bora in <!h4u.
Korea, in t%3. He receival t b B.S. degnc In
electronics acgincerins from Seoul Nitmnal University. S i u d . Korea. in 1975. and the MS.and
Ph.11. d8:greqs in electrid and computer e@
nrcriny fruq tho University of Wisconsin. Madiw n . ~n IY7Yiand 1982. respoc1ivi:ly.
Sinc: IYal he has been mAwsiin1 Profes%>r
in it!< llq~.~r!men!o f Elcctricd Engllieering 11
ihc
l,u\,:nii> <if U.~diinei..n. ScJiik. and
>cr.hs*
Lh.:
t < ~ p ~ . ~ .<i i>mi - t i i ~ . rw.hiteiturC.
p . d i e l cumputcr~ and applicatmnr. i u i n p ~ r ~w íh * )-!cm dcs!pn. d d .
\anted (16- and 32-bit) minocomputer system d c r p . and i m r p rTocrvinp computer syrtcrns. He has drwldprd nim, ncu wniorand grrd.
uate level computer engineering c o u r ~ ai t the l!nivn*ity of Washington.
His research intercrts include wmputcriied impcdmcc h a g i n g , micro-
computer-bas& medical instrumentation, human body modelin@ and
simulation, image and signal proccssbg. and advanced computcr architecture. He is a ninuibuting author to the textbook Design ofMiCr0.
mmputer-Emed Medimi Insrrurnmrofbn W.J. Tompkins and J. G .
Webster, Edr.. Englewocd C W s , NJ: Rcntice-HaU, 1981). and other
books in press. In 1981 he was1 finalist in the student paper wmptitionr at both the SCAMC and ACEMB conferences.
Dr. Kim is a member of the IEEE Engineering in Medicinc and Biology
and Computer Sacktier. the Awciation for Computing Machinery, and
Tau Beta Pi. He ia a Faculty Advisor for the Washington Alpha Chapter
of the Tau Beta Pi Association.
rc""".
..
.
John C. Webuer (M'S9SM'69J r e d v e d the
B S E . degree from CurncU University. Ithaw.
r
m
N Y , i n 1953.andthcMS.E.E.rndPh.D.dcgrcer
from the University of Rochester, Rochester,
NY.in 1965 and 1967.rcspectively.
He is a Professor of Electrical and Computer
Engineering. at the University of Wisconsin,
Madison. in the field of medical inrtrumenlation, he tenches undergraduate. graduate, and
short courses. and does research on electrodes,
biopotcntial amvWieis, impedance measurements, and tactile vieon. He iscoauthor. wilh B. Jacobson. of Medicine
and Clmionl En&ecnnf
(Englewood C W s , NI: Rentice-Hall, 1977).
He is the Editor of M e d i a l Instrumentation: Appliwtion and DeJign
(Boston. MA: Houahton Mifilin. 1978). He is co-editor. with A. M.
Cook, if Cliniml Éngineering: .findpies and h c t i c e s (Englewood
W f s , NI: Rentice-Hall, 1979);wilh W. I.Tomplunr, of Design ofMicrocumputer-Based Medical Insmrrnrntarion (Englewaod C W s . NJ: Ren<-...
'
.,
a
I-
.[..
t,
i
r
I-
s ,
i
,-,
,
'
I. 1,
:rmc
¡Oi
~
A~iiiii:c:tioris of NMR Irnagi!:iy in Hyperthermia:
At1 E\!c?Ii_iationof the Potential for Localized
,.
.
1 issue Heatinig and Noninvasive
,
i
Tern peratu re Mon¡to ring
.
.
-.
h,.I I
I.
',
.
z.i
1 '
,
/I
/I!
Df:NNíS L . t ' 4 R K I R
1
'
, . <
“__-I_
-If h l l H A 5 S > A t l I < ) N S < ’ ~
161
rate o f teniperature increase of about O.OOl°C!s fainiosi
4°C per hour) would result. This heating process is equivalent
to microwave techniques and is not localized by gradients in
the static magnetic field such as are used for imaging. For
imaging purposes. the R F field is only on a small fraction o f
the tinie and the resulting tissue heating should in general be
negligible.
:r’
1
\
111. NONINVASIVE TEMPERATURE
MONITORING
The potential for noninvasive temperature monitoring
arises because the relaxation rates, longitudinal ( T I ) and
transverse (Tl) are both functions o f temperature. The problem o f using the relaxation rates to measure temperature is
complicated not only by the fact that tissue water exists in
multiple compartments between which the relaxation rates
differ substantially. but also by the fact that the rate o f
repetitive measurements is limited by the relaxation rates
themselves. There is therefore a tradeoff between temperature sensitivity, spatial resolution, and temporal resolution.
\
‘
A. Primmy Tempemhrre Dependence
--
The temperature dependence o f the NMR relaxation rates
was predicted by Bloembergen et al. [I31 and demonstrated
experimentally by them and others [14]. Detailed derivations
of the temperature dependence can be found in many text
books [ 9 ] , but for completeness a brief derivation is given in
and
Appendix B. The net result is that the longitudinal (TI)
transverse ( T z ) relaxation rates can be written:
-
1/Ti = 72HzTo/(1 + w87:)
l/T, = -rZ$[r0
+ so/(i + wxs:)]
(3)
(4)
where 7 is the gyromagnetic ratio, H is the local magnetic
field due to local magnetic moments and which therefore
changes with thermal molecular motions, so is a molecular
position correlation time, and wo is the iarmor frequency.
The correlation time so is found to approximately follow the
relationship [13], [I41
ro = constant X d T 2 KIT
(5)
where K is roughly constant as the viscosity q o f water changes
very slightly as a function o f temperature. A plot o f predicted
relaxation times TI and T2 versus correlation time is given in
Fig. 1. From tissue TI measurements made at two frequencies
(24 MHz and 2.5 MHz) by iing eral.. it is possible to estimate
the value of K to be in the range of 2 X IO-” s-K [15].
This is sufficiently small that in the temperature region where
water is liquid (O-100°C) and at frequencies used in NMR
imaging (10-60 MHz), the quantity wore is found to be much
less than 1. Thus, for pure water the relaxations times TI
and Tl are about equal and both arc approximately linearly
related to the temperature. In tissue, due to various factors,
Tlis found to be about a factor of 1 0 shorter than TI [16].
Fig. 1. Plot of expected reiaxation times v c r ~ u sconehtion tinit,.:
i s generally assumed that temperature is inversely rested to
lation time. The minimum in TIoccurs when v u = I .
tion in the magnetization. If the relaxation process is
exponential, attempts to characterize it with a
constant will be inaccurate and will depend upon
and timing o f measurement.
The simplistic model of relaxation given in the
section becomes very complicated when considering
o f protons in tissue. The “inhomogeneity” d
microstructure results in a large variation in water pm
relaxation rates. There is empirical evidence that wate
tissue resides in either bound states (hydration of large m
cules) or free states [IS], [17]. The relaxation rates for
states are found ¡o be much faster than those for wit
free state. bhen multiple compartments (states) exist an
exchange between states occurs, the observed
is the sum o f the magnetization in the various
each compartment decaying with its own characteristic d
time [IS]:
m)
2Piie-”’j
n
=lor
ir!
is I
where P,j is the fraction o f the original magnetization comp.
nent Io, in the j t h compartment. A typical curve for IQ
compartments is shown in Fig. 2(a). When exchange is pc
mittcd between compartments, the separate decay ratis h
come less obvious. in the limit where exchange is very rapl.
(i.e., much faster than the rate o f relaxation) the relaxatiiv
becomes exponential with a single relaxation rate given by
B. Nonexponential Rebarion
The potential for relating relaxation time to temperature
depends upon the existence o f consistent, exponential, relaxa-
--
Lo-,:
1lTaw =
2PijlTj.
n
i- I
i
where I, is tlie equilibrium niagnetiza1ii)n uliicli is determined
by the applied static field. u is the time betueen tite 90'
pulse and the 180" pulse, and b is the time beiweeii successive
90" pulses. The times u and b can be varied independently.
Hliile holding b constarit and measuring I(t) for two values
of a (a = 01. u2j, one obtains for T2
T2 = (ai -uZ)/ln (12/Ii).
(9)
Assuming independence for It and I2 and defining
K =
.'(Ij/G and 3! = (u1 - u2)/Tl the relative variance in T2 can
be obtained as
o2(T2)/T:= Ke2"/r2(e2@
+ 1)/O2.
(10)
The function of /j is minimized when 9, I1 (Le,, when the
time between measurements is about equal to T 2 )having then
a value o f about 9 . The exponential in u1 is minimized when
01 is zero, becoming about I when 01I! T 2 . I f it is assumed
that the relative standard deviation in the maximum signal is
about 1 percent, then K I!0.0001. Using these approximations,
the relative uncertainty in T, can be expressed:
u ( T ~ , ) / TIO.08.
~
(1 1)
In a simidar manner, two measurements of I(2) obtained
for different values o f b(b = bl , h2) while holding a constant
allow Ti t o be computed. The expressions are complicated
for arbitrary b l , b2 but can in principle be solved. If a simple
solution is assumed the relative variance in TI can be computed as
Although the expression in j3 (which is here defmed as j3 =
(b2 - b l ) / T l ) is complicated, i t has a minimum of about O
when fl I! 1.5. Using again K I0.0001, the relative
standard
enor in Ti is given by
o(TIJ/TiI0.06.
(13)
D.Temperature Sensitiviry
The precision with which temperature may be measured
using NMR depends upon the precision of individual relaxation time measurements, on the number of such measurements
which can be made and averaged together, and on the sensitivity (proportionality) between Ti and temperature for the
tissue studied. In a nonimaging study of relaxation time
( T I ) versus temperature, iewa and Majewaka demonstrated
a sensitivity of about 0.8 percent per "C for spleen, heart,
lung and muscle tissues 1211. in the imaging experiments
performed by the author, a sensitivity for blood o f about
1.4 percent per "C was obtained for T I 161. Thus, in order
to measure tissue temperature changes t o within lec, it is
necessary to measure T, to within 1 percent.
An example of potential temperature precision in imaging
is given in the two compartment blood study of Fig. 3. The
Fig. 3. (a) An example of cross-sectional Ti
temperahm difference of about 1S'C. (b)
certainty obtained from an average of five
bars represent one standard deviation for
and conespond to a temperature uncertain1
image is a T~ cross section of two approxinlateiy cy
blood samples, the brighter one maintained a1 ?OeC and
darker maintained at 2°C. The sample cross sections
approximately 1 cm2 . The tempeiature precision camp
from an average of five such scans was ipproxiinately
It was very evident in this study that improved prcc
results when multiple scans are averaged together. Assumir:
the measurements are independent and that the noise bi
zero mean, the precision is improved hy tlie square 10:
of the number of measuremenis included in Uie average.
If it does prove essential to average multiple measure
together, serious timing constraints result when us
' ,
<111': 8
YLI
4
I.$!
,. ,
.'
'1,115.
&retit
1 18
g"'ie:it,
,
I
,
:
8''
, ,
Jture iiicdsurmen:,
a
d .yT i t d l . I'liis. i t TI i r less thin I s. as appears
c;.se i
i
ib i t ) l 6 ~ ~ ~tiuiies.
i,A
JS many .is 60 s e p t a t e
:.Lwretticncs I trcni 'u tiicii TI is coriiputed:l could
ed in onc ii,iiiiiic, :;id;iing
precisicn in tenipara.
other facti,:s
uIi.\:ha r e i t
thc precisian of measure-
icli is b1:iiig ,:c.isured The signal will therefore vary
c r i ~o' .he :iiiciir d::iieniii.in of die volume being
,\11'1 \ D I X .!\
~:-~oio
!mains less than I , the signal can also be
prupor:itonit1 t o the squire of the applied static
&Id, H,, itiie induced signal i s proportional to both
etic moiient and the lreqiiency, both of which are
na1 to tlic .ipplicd ficid). Athough 7 , is found i o
frequcricy in accordance with (3),
is s m l l [ 151 ( w o í o is much less than 1) and
ttle i!flect on i:he sig~al-to-noise ratio. Whereas
experirnenr!i were performed at 0.35 Tesla, curng has heeri successfully performed
d a . an increase in a factor of over 4, corresponding
tbarl an order o f magnitude increase in the signai.10-
ai
omiriuus observation concerning temperature
he data o f Lewa and Majewska [21].
on tissue TI relaxation times versus temperand an irreversible decrease in TI occurring
c. I t wuuld thus a p p e ~ rthat a t the point where
eded, their: is a coniplete lass in
e catise of the d?cre:isa appears t o be a great
fU,ridanien,tally related to the hyperthermia
Pouitile that an abrupt change in TI at just over
be a very precise indicator ofphysiological
' Further re,ieirch i:i clearly justified.
The rate o:' heat abswpti ' r i:i a iti:,.,n(rue :o UMR le,<
nant absorptiuii depeiiili 11: .ti i w se:iara:e ::itej of inn:^^
actions: the rate ;it wlii:l~ ~ ! I : I<€ field úter;icth with i.hs
local magnetic m«meiiti. L I I . ~ 'he 121- at wiiich the lox!
magnetic moments trarisf:i 1' erriial i:nti-gy tsi tli? siirrouriding
environment. In the pro ,e:w< ( c t a lar:c in~piieiicfield Jf,
the degenerate energy lei
.i~;ad,ihie to prm>toriso f spin I / ?
are split into two levels 9
did by l i =l!y€I,,.Thefluctu~
ating local magnetic field. ,Iiic :c the r a n h thermal
~
motions
of neighboring nuclei dila) irieriict \\irh the protori magnetic
moments and cause the-nial quilihritlm, riccording to the
B o l t m a n distribution, t , j 3:: whieved. If' no is defined as
the equilibrium populatioii ,differi:ni:e between the two states
and n is the population d i l f e r x c c ivliich exists a i some instant
in t h e , the return to equilihr,iim in be expressed [9] :
dnfdt = (no.-")/TI.
(AI)
For thermal interdctions, i f i !,iti:ir.s
~
which tend io cstablisheil
thermal equilibriuni occur
sr: xpidly ( o r rnori: often) than
the reverse transitions.
The addition of energy t i ) tlii: !$;?in !;yriem is .iccomplisheil
by the use of an RF ma::ni:i.c fiiid. o~rtliogunalto the static
field. Neglecting thermal k1.x r:ciiloris. in the p:esence i1f the
RF field, stimulated enii 111 ;uid ;ibsorprio;i o,:cur with
equal probability. W 191:
1111
ltn"dt =
itie
~-'
t i t i rdt:
(!,e :.,..,,
e:'
(A')
Wtr.
,,!
.rAn\ltiL,r i,; 11:
.I
:..< !
,111'
:'
',:
,'I
,:I.:
ir df -= u .:
!ields for 11
n = n o / (I
+ ?hT,1.
(A31
The net rate oí energy absorption is
*
d€/dl = fiw Wn = nofiwW/(1 + 2WTl).
644)
Because W is proportional to Hi (the square of the RF
field) 191,the rate of energy transfer is increased by increasing
the RF field strength. Unfortunately, as W increases, the
quantity W/(l + 2 W 7 , ) approaches the limiting value l / 2 T i .
BecauseliyHo is much smaller than kT,the Boltzmanndistribu.
tion reduces to
no = h%7Ho/2kT.
(As)
The rate o f energy transfer becomes
(A61
dE/dt = N y 2 h 2 H i / 4 k l T T , .
For the case of protons in water, N = 0.66 X
protons/
c m 3 , y = 2 . 6 7 5 2 X 108s-1-Tesla-i,6=1.0546X 1 0 - 3 4 J * s ,
k = 1.38 X
J/K, and the temperature is about 3 1 0 K .
For protons in tissue, the energy transfer rate is thus
dE/dt 2 3 X 10-9H?,/Ti
l/s.
APPENDLXB
(A71
(U*)--Io)
where the longitudinal relaxation time is then given by
1iTi = y ' I k x A w o ) + ky,(woIl.
Similarly, the x component of the niagnctization
acccording to
dUx)ldr=1í(1)XHo)x
-y2[kyy(wo)+ kzz(O)]V,)
with
]IT2 = y21ky,(wo) + kzz(0)l.
It is generally assumed that the thermal motions show
short range correlation such that
Hkr)H,fr
T
+ T ) =H ~ e - l r l / r o
where the bars imply ensemble average, the subscript
sents one o f the components x,y, or z, and TO is the
tion time of the motions. The power spectral density.
obtained as the Fourier transform of the correlation func
is therefore given by
Bloembergen demonstrated that, for a system of molecules
of identical magnetic moments, the relaxation of the system
k,Xw) = H f r o / ( l + w2r;).
to thermal equilibrium is accomplished through the random
Brownian motions of the molecules [13]. If, for example, It is also generally assumed that the various coniponcnk
the system of molecules is held rigidly, with only motions the fieldHi are equal. The relaxation rates can then be writ
(rotations) of the magnetic moments of the nuclei are allowed,
the only interactions between the nuclei which can occur are
1/T1 = y2H%o/(1 4- W?,7;)
those which do not change the total energy of the system
1/T2 =r2H2[ro TO/(^ + U?,.?,)].
(Le., those which do not change U,).the average z component of the magnetization). When motions of the molecules
ACKNOWLEDGMENT
are allowed, transitions can occur which transfer energy
In addition to others previously acknowledged,
between the system of magnetic moments and the molecular
motions and which therefore lead to thermal relaxation o f suggestions have been received from C. Durney, D.
the z component of the magnetization. B y taking ensemble and D. Christensen of the University of Utah.
averages o f the possible molecular motions, the power spectral
and k,,(w) of cordensity Components k,,(w), &,,,,(u),
REFERENCES
responding components of the fluctuating magnetic field at
[I]E. M. Purcell. H. C . Tomy. and R. V. Pound. "R~SOMKI b
a typical nucleus can be obtained. It is easy to show that
sorption by nuclear magnetic moments in I solid." Phys. Rrv.. *D
69. p. 37. 1946.
only the x and y components have an effect on U,),the y
121 F. Bloch. "Nuclear inducrion." Ph,vs.Rev.. WI.70. pp. 4MU';
and z components affect <I,),and the x and z components
1946
._
affect U,). Furthermore, only components o f the power
131 E. L. Hahn. "Spin echoes." P h k Raw. w .UO. nu. 4 . F
58CL594, 1950.
spectrum which represent a local magnetic field which is
141 P. Mansfield and P. G . Monis. NMR I m q i n p tn BirimrdiiW
stationary with respect to the precessing moments will have
New York: Academic. 1982.
any nonnegligible long range effects. Because the expecta151 L. Crooks. L. Ksuimin. md A . Marpulir. NMR lrnupinp in YW
tion values o f the magnetic moment components form a
cinc. New York: IgakuJhoin. IVn1.
I61 D. L. Parker, V. Smith, P. Sheldon. L. E Criwb. iind L. F u S i
vector which precesses around the static field at the iarmor
"Temperature dirinbutian measuxmcnir in iuo-dinicowonil hM'
frequency. wo = yHo, the components which are stationary
imaping."Mcd. Phw.. vol. IO. no. 3. pp. X I - X S . IY83.
with respect to the precession are k,,(wo), k,,,(wo), and
171 K . S. h c r and R. Damadiui. "NMR in cancer: IX.T k mrt
-
I
3
....
....
J.
O
'I
1
<
!,
I.
L
L
.......
.........
. . . . . . . . . .
.....
~
.....
--_.. ....--.....
-<.,.,................
................
-,,,
,_"
b
91I
I
ru
h
(a)
.
(C)
(b)
Tip. 1. Three arrangements of cunent Imps and the conerpondinp d$
rcctions of magnetic Yield lines arc shown (a) Single-turn c o i l (b)Coaxial pair ofcoüs. (c) Concentric c o t
-
assigned values of complex admittance to cells of tissue,
as represented on computed-tomographic scans of human cross
sections, to obtain a three-dimensional model of SAR.
The essential features of the SAR distribution in tissue
produced by a single-turn coil are that the SAR rises from
values of zero along the coil axis to maximum values at distances from the axis similar t o the coil radius. The maximum
SAR in any plane perpendicular to the axis diminishes with
increasing depth into tissue (or distance away from the plane
of the coil), within a region o f fixed complex dielectric permittivity 121, [3].
The improvement in SAR at a given depth that results
from using a coaxial paU of coils can be estimated from Fig.
2 for a pair having a radius of 10 cm and a separation of 34
cm. The ratio of maximum SAR on the skin surface t o maximum SAR at the body midplane for varying coil radius a ,
coil separation of 34 cm, and body diameter of 30 cm is
obtained approximately from Fig. 3 by multiplying the values
on the ordinate by the ratio of electrical conductivity for
superficial tissues by the conductivity for viscera. The coil
radius required for maximum midplane SAR of more than
25 percent o f maximum superficial SAR is > 10 cm. Standard
formulas were used for the calculation of the magnetic fields
in this example 1171, and the approximation results from
using SAR a$IF&
electrical conductivity, and by ignoring
effects of finite load size upon SAR, as will be discussed next.
When the load has finite extent in the plane perpendicular
to the coil axis and also is noncylindrical in this plane, the
SAR distribution has the general features described above,
but with possibly marked variation in SAR at a given radius
from the coil axis resulting
- from electric fields associated
with charge displacements onto the boundaries of the load,
as illustrated in Fig. 4.
Numerical techniques are essential for elucidating the SAR
distributions in the case of single or paired coils with finite,
noncylindrical loads, in order for appropriate boundary conditions to be satisfied. The deviations in SAR from the toroidal
distribution predicted for semiinfinite loads. increase as the
coil diameter becomes similar to the minimum load dimension in a plane perpendicular to the coil axis. This conclusion
is based upon a series of phantom heating experiments w e have
done at the University of Arizona.
The highly nonunifom SAR produced by magnetic induc~
~~~
wh . 4 . ~ ~
iwuh * w
.torn R.U
--- 'Dm
U
..
.I
I
W
6
z
O.
2
e
I
z kml
-- -- ----_
IZ
u
16
Fig. 2. The squared value of axial magnetic fieid, in arbitrary I
evaluated at a mdius of 10 m tor a coil pair with radius of 1
and reparation of 34 cm ( s o u h e ) is shown versus the i x i
tan= z from the pkne of one COL
Similarly the results for I#
coil of 10 cm radius are shown (dotted Une).
Fw. 5.
Un6a
inten
nnu
The c
'
I
~
Fig. 3.
u&l
6cld
*,, wlun(cv~l
a1 a ndiusa of a coil pait of radiur a separated by 34 cm) u#
(skin a<rface) + H2 (body niaplane) I V ~ I S Uhlul
.
bled as
ing the ratios of @ by resp&ive tissue elccViwl conducti
an utimstc of the mrio oT SAR nlucs
uiñaee to
pknc.A Foilmdiu~of>10 cm i r r q u u o d for sdnnagmusratl
tion, particularly in the c a s o f the pancake coil or pairec
arrangements, has led t o the suggestion by von Ard
1181 that the SAR may be time averaged to mure un?
values by scanning coils over the body region of intc
Other simple phantom experiments at die Univeriit!
Arizona lead us to be skeptical that SAR disiribuiions ca
dteend.
scannin,
from di
Iir dab
ofthc
i c i iir iiurnericd so:utions of ikic lii.)b.ear e<iii.Ltibn (hce the
thy Strohhsiin and Roemer i n :!lis isme). I r , I>,LI:~s~iliii:ic;ri>, niodels niiist be choien h r iri!r~tutn<iral 5k)<><!
flow
rates 2 n d distrih.iiii>ns, and 11c>n1i.i11:ssiic blo,id nou rates
!nus: be par;iinetii-!red as well [241. 1251.
The temperatriie distribiitioris iin I I O I P ; ; ~ti.,sui ' obtained
w t t i a Iielicd p:incakc cod were :d:ulatei
hy lirrid et ai.
1:31 u\irip ail aridytical solutiixi tiir SAK logediet Uitli a
:iiiii:e-dirfererice iiiiirie:iciil metliiid ,of solving i i 6 bioheal
:quaAm. These .:iuthors studied 111: cflect 01' coü tile. coil>kin >c.paratiun, !at tliickncss, mid hicocilirig ~orit~itiiins
iipoii the tempcratiite distribution. Itripioiie<i I citing at
ieprli relative 1:) superficial tissiics rwdtud fro,< a larger
.!itxi
d
.dwri
I
.L
:,
!.\is;.t
11.
.id
reliably by means o.f
pattern resulting
the influence of
1
Ill,,,:,:
'.#
e in SAR distri.
s less intuitively
SAR in a given
'Ik.;
[I
t.
>:
I , , I!IC
iiiagnetic field intensity
iurfacc is >92 percent
gnetic skin depth
~ i i: dl l i u s , and the temperature distrihuticic caicdlated f o r
.ilti$c!e foUowed the toroidal SAK pdtterii chisely. In the
' a t la!er, howeier, steady-state ierriperaí~ire diskibutions
.i:flwicd the effect o f heat transfer procerser and #:onformed
.i:ss W e i i i o the S A R h a n did the ieriip,eratiire d6tr;bution in
11111scic Excessive temperature rise i n the in! layer resulted
irom rclatively h a h SAR values tiigether wit11 Iciwei. perfusion
ia1e.i rlian in the deeper muscle layen, a pn;,l>lenithat was
menruated with increasing fat thickness. <:oo!inp o? the skin
w i t h cliiued water at 10°C, however, cu iid dEplace the
maxkniim temperature 1.5 cm deeper that, the r';;it-murle
iitertace. assuming ii i cm thick fiit Iayei.
The normal tissue temperature di..:ribui,ionii obtained
.*.it11 ,,iitde pancake c<irlssuggest that elíecti;r iunlcr heating
:(iuldt e obtained ori,.y for tumor; cc,ritinec r,o a few centi.
':ietci> dcplli from t h e skin, and thar. !,k:in 8.u,;~lin{:
,drerr the
;l:wr;.ttue distribilti~>nsignificanti\ cmrily iri tlhe m'ict íiiperI'
\i
:. ,. , ' ,.c f r o m die axis than
tumor niudri (IOU perfurlon in cmlral zune. high
perfusion in outer zone) with scanning of the coil over the
tumor bearing tissue. With such a model. intratumoral temperatures 242°C could be achieved in a 2 cm radius X 2 cm
len?th cylindrical tumor extending to 3 cm below the skin
surface.
The reports of Hand and colleagues are valuable for defining conditions under which this magnetic induction method
can produce therapeutic temperature elevations (>42'C)
in tumors, and for revealing the rather limited application of
the small radius pancake coil method to treatment of small
superficial tumors.
Similar bioheat analysis for tumor and tissue temperatures
with a paired coil arrangement have not been reported, and
would be markedly more difficult to perform accurately bec a w of the complex SAR distributions associated with this
arrangement, the fmite load size effects, and the greater
variety of blood perfusion rates that would probably be
present in large tissue volumes.
Modeling o f temperature distributions obtained by magnetic
induction with concentric coils has been reported by Strohbehn
1281, Brezovich ez of.1201, Halac et ni. 129) ,and by Paulsen
er al. 1301. These models all include tumors of varying size,
blood perfusion, and depth from the skin surface, and differ
somewhat in the method of calculating SAR and solving the
bioheat equation.
The aim of such modeling, as indicated previously, is to
calculate intratumorai temperatures likely to be achieved
for conditions simulating clinical practice in which maximum
temperatures in normal tissues are limited to 42-44OC, depending upon tissue type. Reasonable values of conductive
or convective heat transfer across the skin surface may also
be included to model the clinical use of forced air or chilled
water cooling.
Only the study by Paulsen et al. has included numerical
methods of calculating electric fields in tissues with numerical
bioheat equation solutions. This,in principie, allows the effect
of areas of excessive heating to be included in the analysis.
Excessive heating can result from the presence of fat, bone,
and air volumes in the superficial tissue that ])can deviate
eddy current flow and produce h& current densities in surrounding high water content tissues (analogously to a parallel
electrical circuit) and 2) can result in predominant eddy current flow perpendicular to tinue interfaces and excessive
heating in low water content tissue (analogously to a wries
electrical circuit). On the other hand, the fact that induced
electric fEldr are, on average, tangent to the major annular
tissue interfaces in the body is an advantage o f the electric
field configuration produced by magnetic induction, as Elliott
ef al. have observed 171.
The conclusions of the referenced papers on bioheat
transfer modeling are similar and consistent and can be summarized as follows.
I) Magnetic induction heating with a concentric coil
produces the maximum SAR and maximum normal tissue
temperature elevation in the outermost 5-6 cm of tissue.
With blood perfusion values typical of resting muscle (2.7
m l i l 0 0 r m i n ) , homogeneous perfusion, and a cylindrical
patient with radius of 15 cm, Strohbehn [28] found that
.a
IKU-ZUIIC'
x.Iieii rlie maxmium
.
I
(arteri,,
blood temperature 37OC) a t a dcplh of 1.5 cm. the b,,dil
center temperature was 38.6"C in stead! state.
t
Maximum temperatures in necrotic tunam can cxcC
ec
42°C for sufficiently large tumors (eg.. 4.5 cni radius) evg
at the center o f the patient. although the time required to'
reach temperatures X 2 - C by thermal conduction can &,'
quire long periods of time exceeding 60 min. The edge
nonperfused tumor in Strohbehn's model would not re*'
temperatures >42"C.
2) Portions of spherical, uniformly perfused tumors pir.
rounded by lung in the model of Brezovich el of. 120)
reach >42"C for tumor radii >5 cm and for values of S&
that produce temperatures near 42'C in subcutaneous fat and
chest wall muscles. lntratumoral temperatures are predktM
to be nonuniform and minimum temperatures >42OC at ch<
tumor-lung interface are unlikely, especially at the poj,,
regions of the tumor. The maximum temperature in turno,,
<5 cm radius may not exceed 42°C. Cooling o f the sum.
ficial tissues is important for elevating applied power levy
t o maximum values.
3) The model o f Halac et al. 1291 considered tumon al
uniform or annular patterns of blood flow surrounded
viscera, muscle, or fat, as would b e the case for pelvic and
abdominal tumors. Solutions were obtained for three valua
of the tumor blood perfusion rate. the two perfusion pattern;
three tumor positions, three tumor sizes. and three no
tissue blood perfusion rates. Particular solutions were idenql
fied where all intratumoral temperatures could be elevatedi
to >42" without exceeding 44'12 in muscle and fat or 42.4
in a significant volume of viscera. The principal fmdings w q
that proper. tumor heating was achieved only when most d
the tumor was within the superficial muscle tissue, this in tun
limited tumor size to a diameter of 2 un. No proper i d
heating was found for any tumors that had a margin extend'
to the center of the body. Only 11 percent of al1 cases
which the tumor was contained within the visceral annul4
(IO cm radius) were properly heated. In a majority of cas%
applied power levels were limited by excessive temperatura
rise in superficial muscle and fat annuli. Similarly to the c o b
clusions o f Brezovich et al., these authors concluded that
marked temperature elevation of necrotic tumor cores i
i
possible, but portions of the tumor periphery are usually
below 42OC.
The study of Paulsen er aL (301,including tumor models
in both lung and viscera, corroborates these conclusions.
issue ieriipcrxiure nd<i 45°C
9
1
LABORATORY
INVESTIGATIONS
Magnetic induction methods have been studied in phanrmi
[19],1271, [31] and in large animals (31]-(33], and such
studies are an important aspect of the physical cliaracteriri,
lion of any hyperthermia technique. Nonperfused phantom
studies are useful for revealing SAR patterns. as Cuy ha~
demonstrated in analysis of microwave applicators 1341. The
principle involved is that of construct in^ electrically accur~te
phantoms modeling tissue properties so that the teniperaturc
rise produced during a brief heating interval is proportiona!
to SAR. Temperature distributions after heating c m be oh
served accurately with split phantums and therniogrnphk
..
96
t i I I I H - \ Y S A < T I O \ ~ O \ I~IO:II.IKA~.
t i ~ e r n ~ m i c i r in
y order to quantitate the ctricac) of h!per.
i l i c n i i i a therapy and to assure quality. This prognostic inipuriance of niininiuni temperature. i f also true for human
tuni~irs. justiíies the need for assessing ability of Various
hyperthermia devices to achieve minimuni temperatures
of therapeutic vplue (>42’C) in theoretical modeling studies.
In the work of Baker eral. [46], 1 1 8 patients were treated
with a concentric coil. Maximum tumor temperatures 2 4 3 ’
were observed iii 21 o f 99 patients. Minimum temperalure
data were nut reported.
The experience of Twoomey and Frey 1441 in 19 patients
with a concentric coil revealed that the temperature o f at
least one intratumoral site exceeded 42OC in about 1/3 of the
patients. with a trend of lower temperatures with increasing
depth and decreasing tumor s u e .
Corry, Meoz, and collaborators [36], [37], [50] have
clinical experience with use of single or paired coils in superficial. intrathoracic. and visceral sites. In 16 patients with
tumor diameters >5 cm, 33 o f 50 superficial tumors had
intratumoral temperature? a42OC, and m 1 1 of 26 deep
tumors, temperalures were >42’C. In nine patients with
intrathoracic tumors, average temperatures were X 2 O C
in 30 percent o f hyperthermia sessions. Thermometry in this
latter series could be done at few sites because of the limitations associated with intraoperative thermocouple placement.
Use of a single pancake coil for treatment of superficial
lesions has also been reported by Kim erni. 1431 Thermometric
analysis o f this series was described by Antich qr u/. 1511.
These authors investigated the possibility of correlating
temperatures with S A R in both tumor and normal tissue
sites. For given S A R , intratumoral temperatures were higher
than in normal tissue in 213 of. the cases. The correlation
o f S A R and temperature was higher in the case of normal
tissue than in that of tumors. Their conclusion was that
blood flow rates in tumor are frequently lower than in normal
tissue, in part because o f thermoregulatory vasodilation in
normal tissue. Variation in values of average tumor blood flow
rates relative t o normal tissue weaken the correlation between
S A R and average blood flow in the former case, but close
correlation could still remain for minimum tumor temperature and SAR.
i ~ ~ , ~ ~ i ~ ~ , i ~ i ~ ~ , . \~~ . ~J iA..&)<yIp
Y. n
~ ~ ,!:~ i : ~ i . v u
‘ii’OLI.SON:’
Small p m i a k e coils are an eflcr.iivc nican, r d lieak
small tumors with dimeiisions <4 cni i n ihr musi supcflrk
several centimeters of body tissue. Largr dimieiei D ~ J ~ ,
paired coils niay produce higher S A R at given depths th%
concentric coils. These coils produce a toroidal S A R discrib,
lion that is complementary t o ihal produced by ConcrnN
coils. The sites, depths. and tumor sizes appropriately trepb
wiih paired coils reniain to be defined.
r
ACKNOWLEDGMENT
S. McFarland typed themanuseripi.K.Crochowskipre
illustrations, and J. Conrad and A. Fletcher assisted
laboratory and clinical studies.
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concentric coils. Limitations o f induction methods for treat- I 181
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~
~~
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! i
I LL'
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