image gently how can you help?

IMAGE GENTLY
HOW CAN YOU HELP?
Keith J. Strauss, MSc, FAAPM, FACR
Director, Radiology Physics & Engineering
Children’s Hospital Boston
Harvard Medical School
Acknowledgment
Marilyn J. Goske, MD
Robert Pizzutiello
INTRODUCTION
A.
B.
C.
D.
Introduction to Image Gently
Image Gently Focus
Pediatric Considerations
Your Involvement
1. Training
2. CT Patient Dose Index?
3. Pediatric CT Scan Parameters
The Alliance ….
A. Coalition of health care organizations
dedicated to providing safe, high quality
pediatric imaging worldwide.
B. Primary objective is to raise awareness of the
need to adjust pediatric radiation dose.
C. The ultimate goal of the Alliance is to
accelerate the change of local practice.
1. Scientific observation to local practice
change ~ 17 years!1
1Greenberg
SB. Trans Clin Climatol Assoc 119:2450261, 2008
What is Image Gently? A Campaign…
• Of education and awareness
• To improve radiation protection for children
How much do we really understand?
Under estimation by 75% of MDs!
Lee et al. Radiology. 2004; 231:393-398
PARTNERSHIPS
A. 42 Affiliates; 13 International; > 700,000 individuals
Academy of Radiology Research
American Academy of Pediatrics
American Institute of Ultrasound in Medicine
American Osteopathic College of Radiology
American Registry of Radiologic Technologists
American Roentgen Ray Society
American Society of Emergency Radiology
American Society of Head and Neck Radiology
American Society of Pediatric Neuroradiology
Asian-Oceanic Society for Paediatric Radiology
Association of University Radiologists
Australian & New Zealand Society for Paediatric
Radiology
Canadian Association of Medical Radiation
Technologists
Canadian Association of Radiologists
Canadian Interventional Radiology Association
Canadian Organization of Medical Physicists
Coalition for Imaging and Bioengineering Research
College of Radiology, Academy of Medicine of
Malaysia
Conference of Radiation Control Program Directors
European Society of Paediatric Radiology
National Council on Radiation Protection and
Measurements
North American Society for Cardiovascular Imaging
Radiological Society of North America
The Royal Australian and New Zealand College of
Radiologists
Society of Interventional Radiology
Sociedad Latino Americana de Radiología Pediátrica
Society for Pediatric Interventional Radiology
Society of Computed Body Tomography and Magnetic
Resonance
Society of Gastrointestinal Radiologists
The Society of Nuclear Medicine
The Society of Nuclear Medicine - Technologist Section
Sociedad Mexicana De Radiologia E Imagen
Society of Radiologists in Ultrasound
Society of Uroradiology
IMAGE GENTLY’S FOCUS
A. Positive, unified message
1. Vetted through Alliance member committees
2. Adds depth, clarity, and credibility.
B.
Consistent tone
1. Respectful to all
a.
b.
Medical professionals and
Families
2. Seeking information about patient radiation
doses.
IMAGE GENTLY’S FOCUS
Managing Patient Dose in CT Holistically
Configuration of CT Scanner
Radiation Dose / Image
Radiation Output Calibration
Operation of CT
Tissue Volume Irradiated
Should CT be Performed?
Image Quality Verification
Automatic Exposure Control
Exam Specific Acquisitions
Scan Length?
Contrast Media Management
Total Patient Dose from CT
IMAGE GENTLY’S FOCUS
C. Advocacy issues include:
1. Improved education regarding radiation risk
2. Promotion of standardized
a. Nomenclature of technique parameters
b. Radiation dose utilization (technique factors)
c. Radiation dose display
3. Improving medical literacy for parents and
patients.
a. Medical Image Record Card
b. Educational brochures for parents
- Multiple translations
IMAGE GENTLY’S FOCUS
Working together to change practice
Medical
Physicist
Radiologic
Technologist
Radiologists
Imager
vendor
GROWTH OF MEDICALRADIATION DOSE
A. Early 1980s Snapshot
1. 15% of Annual Radiation
Dose due to medical
imaging
2. 0.53 mSv per year
a. X-rays:
0.39
b. Nuc Med: 0.14
Consumer
Products
3%
Nuclear Medicine
4%
Medical X-rays
11%
Radon
54%
Internal
11%
Terrestiral
8%
Cosmic
8%
Adapted from Mahesh
Other
1%
Procedures vs Effective dose contributions
Interventiona
2%
CT
12%
Nuclear
Medicin
e
Radiography &
Fluoroscopy*
83%
Radiography &
Fluoroscopy*
19%
Interventiona
l
CT
46%
Nuclear
Medicin
e
Percent Procedures
Effective Dose Contributions
17% of All Exams Deliver 81% of Total Effective dose
91% of Pediatric Dose in the ED comes from CT
Adapted from Mahesh
Preliminary estimate of changes in
Medical radiation exposure to US population
US 1980*
US 2006
Other
0.06
Interventional
0.4 mSv
Radiography
0.6 mSv
Medical
0.54
Nuclear
Medicine
Natural
3.0 mSv
Medical 0.54 mSv per capita
Total 3.6 mSv per capita
* NCRP 93
Natural
??
(3.0 mSv)
CT
1.5 mSv
Medical 3.2 mSv per capita
Total ?? mSv per capita
Adapted from Mahesh
IMAGE GENTLY’S FOCUS
E. Newest Development
1. Image Gently in Pediatric Interventional
Radiology
F. Currently Under Development
1. Pediatric Nuclear Medicine
2. Pediatric CR/DR
3. Pediatric Fluoroscopy
PEDIATRIC CONSIDERATIONS
A. Radiation Induced Cancer Lifetime Risk
From 1 Sv Dose
1. Average
a. 5% Males
b. 6% Females
2. First Decade
15%
3. Middle Age
2-3%
4. Children 3 – 5
times more sensitive
Adapted from Hall
PEDIATRIC CONSIDERATIONS
Radiation Risk based on Effective Dose?
A. Almen and S. Mattsson, J. Radiol. Prot. 16 (2), 81-89 (1996).
Somatic risk
%/Sv
Hereditary risk
%/Sv
Total risk %/Sv
Children
Aged 0-9
14.5
2.5
17
Children
Aged 10-19
8.5
2.5
11
Whole
population
5
1
6
PEDIATRIC CONSIDERATIONS
B. Pediatric Patient Size Variation is Large
Abdomen
1. 5 yr old:
10 – 17 cm
2. 15 yr old:
14 – 24 cm
RADIATION PROTECTION
FOR CHILDREN
“ONE SIZE
DOES NOT FIT ALL”
PEDIATRIC CONSIDERATIONS
PEDIATRIC ANATOMICAL CONSIDERATIONS
Large Adult
Adult
5 year
1 year
Neonate
5 cm
1 HVL @ 120 KVP
1 HVL @ 70 KVP
ASSUME 5 CM TISSUE HVL
Abdominal Girth
(kg) Mass
PA (cm)
# HVL
LAT (cm)
# HVL
Neonate
2
6
1.2
6
1.2
Newborn
3
9
1.8
10
2
1 yr
10
12
2.4
14
2.8
5 yr
19
16
3.2
22
4.4
12 yr
31
18
3.6
27
5.4
Adult
68
22
4.4
33
6.6
Adult
100+
35
7
48
9.6
PEDIATRIC CONSIDERATIONS
•
Clinical dynamic range of mAs per image to
maintain a fixed kVp
– PA projection
•
•
6 HVL
Range of 64
– LAT projection
•
•
9 HVL
Range of 512
PEDIATRIC CONSIDERATIONS
CTDIvol—Tube Current Changed by
Weight or Mass
PEDIATRIC CONSIDERATIONS
CLINICAL EDUCATIONAL MATERIALS
Table II: mAs Reduction Factors for the Pediatric Head
Room #:
kVp
Head Baseline:
fill in
PA Thickness
(cm)
Approx Age
12
newborn
16
2 yr
17
6 yr
19
med adult
CT Unit:
Date:
mA
fill in
Time (sec)
Pitch
Filter
fill in
fill in
fill in
Head
mAs Reduction Factor (RF)
Estimated mAs = BL x RF
0.74
#VALUE!
0.86
#VALUE!
0.93
#VALUE!
1
fill in
IMAGE
GENTLY
HEAD
1. Type in baseline head techniques and mAs in yellow cells
2. Spreadsheet will calculate mAs estimated for pediatric patients of varying sizes
Table II: mAs Reduction Factors for the Pediatric Head
Room #:
CT Unit:
kVp
120
Head Baseline:
PA Thickness
(cm)
Approx Age
12
newborn
16
2 yr
17
6 yr
19
med adult
Date:
mA
150
Time (sec)
Pitch
Filter
2
1
fill in
Head
mAs Reduction Factor (RF)
Estimated mAs = BL x RF
0.74
222
0.86
258
0.93
279
1
300
1. Type in baseline head techniques and mAs in yellow cells
2. Spreadsheet will calculate mAs estimated for pediatric patients of varying sizes
PEDIATRIC CONSIDERATIONS
CLINICAL EDUCATIONAL MATERIALS
Abdomen
Baseline:
PA Thickness
(cm)
9
12
14
16
19
22
25
31
kVp
fill in
Approx
Age
newborn
1 yr
5 yr
10 yr
15 yr
small adult
med adult
large adult
mA
fill in
Time (sec)
fill in
Abdomen
mAs Reduction Estimated mAs =
Factor (RF)
BL x RF
0.43
#VALUE!
0.51
#VALUE!
0.59
#VALUE!
0.66
#VALUE!
0.76
#VALUE!
0.90
#VALUE!
fill in
1.0
1.27
#VALUE!
Abdomen
Baseline:
PA Thickness
(cm)
9
12
14
16
19
22
25
31
Pitch Abdomen
Pitch Thorax
fill in
fill in
Thorax
mAs Reduction Estimated mAs =
Factor (RF)
BL x RF
0.42
#VALUE!
0.49
#VALUE!
0.57
#VALUE!
0.64
#VALUE!
0.73
#VALUE!
0.82
#VALUE!
0.91
#VALUE!
1.16
#VALUE!
kVp
120
Approx
Age
newborn
1 yr
5 yr
10 yr
15 yr
small adult
med adult
large adult
mA
400
IMAGE
GENTLY
BODY
Time (sec)
1
Abdomen
mAs Reduction Estimated mAs =
Factor (RF)
BL x RF
0.43
172
0.51
204
0.59
236
0.66
264
0.76
304
0.90
360
400
1.0
1.27
508
Pitch Abdomen
Pitch Thorax
1.25
1.5
Thorax
mAs Reduction Estimated mAs =
Factor (RF)
BL x RF
0.42
202
0.49
235
0.57
274
0.64
307
0.73
350
0.82
394
0.91
437
1.16
557
IMAGE GENTLY NEEDS YOU
TRAINING
Complete training fosters
–
–
–
Full use of equipment design
Improved image quality
Reduced radiation
dose
IMAGE GENTLY NEEDS YOU
TRAINING
•
Training is only as effective as the trainer’s
understanding of their trainees
– Each trainee may have
a bit different perspective!
YOUR HOUSE as
seen by...
Yourself
Your Lender
Your Buyer
Your Appraiser
Your Tax Assessor
IMAGE GENTLY NEEDS YOU
CT Patient Dose Index?
A. Limitations of CTDI
1. CTDI100 measured with 100 mm pencil chamber
a. Two Standard
Phantoms
b. Scanner Dose
Index
c. Allows comparison of radiation
output of
different CT scanner models & manufaturers
IMAGE GENTLY NEEDS YOU
CT Patient Dose Index?
A. Limitations of CTDI
2. CTDIvol (mGy) responds to changes in:
a. Scanner Design
i. Bow Tie Filter Composition & Shape
ii. Focal Spot to Detector Distance
b. Scan Parameters
i. kVp
ii. Pitch
iii. mAs
c. Patient Size?
NO
CT RADIATION DOSE
BODY, 32 cm.
HEAD, 16 cm.
100
100
100
90
100
100
50
100
100
CTDIvol = 97
Adapted from Frey
CTDIvol = 84
100
IMAGE GENTLY NEEDS YOU
CT Patient Dose Index?
A. Limitations of CTDI
3. CTDIvol (mGy) does not respond to changes in
Patient Size!!
a. IG recommendations deliver similar patient
dose independent of patient size
Abdomen
Baseline:
IMAGE
GENTLY
BODY
PA Thickness
(cm)
9
12
14
16
19
22
25
31
kVp
120
Approx
Age
newborn
1 yr
5 yr
10 yr
15 yr
small adult
med adult
large adult
mA
400
Time (sec)
1
Abdomen
mAs Reduction Estimated mAs =
Factor (RF)
BL x RF
0.43
172
0.51
204
0.59
236
0.66
264
0.76
304
0.90
360
400
1.0
1.27
508
Pitch Abdomen
Pitch Thorax
1.25
1.5
Thorax
mAs Reduction Estimated mAs =
Factor (RF)
BL x RF
0.42
202
0.49
235
0.57
274
0.64
307
0.73
350
0.82
394
0.91
437
1.16
557
IMAGE GENTLY NEEDS YOU
CT Patient Dose Index?
A. Limitations of CTDI
4. CTDI doses UNDERESTIMATE pediatric doses:
creates false sense of security
a. New Born vs Adult
dose display error
i. Head: ~ 35%
ii. Thorax: ~ 175%
iii. Abdomen:~200%
IMAGE GENTLY NEEDS YOU
CT Patient Dose Index?
A. Limitations of CTDI
4. CTDI doses UNDERESTIMATE pediatric doses:
b. Solution: Pediatric CT Physics Work Group
i. Group within Medical Imaging & Technology
Alliance (MITA)
Developing Correction Factors to estimate a
Patient Dose Index from CTDIvol as a function
of patient size
ii. AAPM Task Group
Developing standardized
recommendation
that can be universally adapted.
IMAGE GENTLY NEEDS YOU
CT Patient Dose Index?
A. Limitations of CTDI
5. No uniformity of display currently exists
among CT Scanner manufacturers
a. Incomplete information
b. Confusion among Users
IMAGE GENTLY NEEDS YOU
CT Patient Dose Index?
6. Actual Displays
a. CTDIvol in mGy
IMAGE GENTLY NEEDS YOU
CT Patient Dose Index?
6. Actual Displays
c. CTDI: Which one?
d. DLP with units
CURRENT DOSE DISPLAYS
6. Actual Displays
e. CTDIvol Units?
f. How does Eff. DLP differ from DLP?
CURRENT DOSE DISPLAYS
6. Actual Displays
g. CTDIvol & DLP with units
h. Phantom size identified!
i. Is only DLP additive for multiple series?
4. Does the vendor bother to
to teach this information?
IMAGE GENTLY NEEDS YOU
CT Patient Dose Index?
A. Limitations of CTDI
7. Dixon’s challenge to 100 mm pencil chamber
a. A New Look at CT Dose Measurement:
Beyond CTDI Med Phys 30(6) 2003.
b. Restructuring CT Dosimetry—A Realistic
Strategy for the Future Requiem for the
Pencil Chamber Med Phys 33(10) 2006.
IMAGE GENTLY NEEDS YOU
CT Patient Dose Index?
A. Limitations of CTDI
8. Boone’s response to 100 mm chamber dilemma
The Trouble with CTDI100 Med Phys 34(4) 2007.
a. 100 mm chamber
underestimates
the dose for all
scans, 40 mm vs
a 10 mm fan
beam.
IMAGE GENTLY NEEDS YOU
CT Patient Dose Index?
B. Solutions to Limitations of CTDI
1. Point Chamber Measurement of Dose
2. Develop agreed upon correction factors to
estimate and display Patient Dose Index
3. Simplify and standardize dose displays on
CT Scanners
IMAGE GENTLY NEEDS YOU
CT Pediatric Scan Parameters
A. AAPM CT Dose Summit
1. Atlanta at end of April
2. All 11 hours of presentations will be in AAPM
Virtual Library
3. Clinical Users Need Help Setting Up Scan
Parameters
a. Not a simple endeavor.
b. ACR CT Accreditation
IMAGE GENTLY NEEDS YOU
A. Conclusions
1. Image Gently is an Awareness Campaign
2. Vast majority of Pediatric Imaging Occurs in
Adult facilities
3. Children are not small Adults . . .
4. CT Patient Dose Index Function of Size
5. Help Clinicians with CT Scan Techniques
Now
6. Children are not small Adults, but . . .
. . . Most Adults are BIG Babies!
Working together to improve radiation protection for children worldwide!
Don’t forget to “Image Gently” and “Step Lightly”.
www.imagegently.org