9-4 Ying Zhu

Fabrication of a Small Animal Restraint
for Synchrotron Biomedical Imaging
Using a Rapid Prototyper
Y. Zhu, H. Zhang, R. McCrea, B. Bewer, S. Wiebe,
H. Nichol, C. Ryan, T. Wysokinski, and D. Chapman
Biomedical Engineering
University of Saskatchewan
Synchrotron
S
h t
R
Radiation
di ti I
Instrumentation
t
t ti 2007
Baton Rouge, LA, April 27, 2007
1/14
Motivations
„ Motion artifacts are of p
primary
y concern in biomedical imaging.
g g
„ The study may require extended periods of time
„ The study may require positioning accuracy.
g movements.
„ Animals under anesthesia continue to make breathing
„ Motion may blur the image and reduce image quality.
„ Excessive restraint increases morbidity and mortality.
„ A well designed physical restraint is of great importance
2/14
Head restraints
Types of head restraints found in literatures:
„ Rigid mounting of the bone or skull through the skin
A.M. Wyrwicz, et al., Mag. Reso. in Med. 44 (3) (2000) 474.
„ B
Box or cylinder
l d restraints with
h ear pins and
d sometimes
a bite bar.
M.W. Bidez, et al., J. Biomech. 27
(10) (1994) 1271.
3/14
Head restraints
Types of head restraints found in literatures:
„ Rigid mounting of the bone or skull through the skin
„ B
Box or cylinder
l d restraints with
h ear pins and
d sometimes
a bite bar
„ Plaster or resin molds taken directly from the animal
K.D. Faulkner, Aust. Dent. J. 20 (1) (1975) 19.
3/14
Head restraints
Types of head restraints found in literatures:
„ Rigid mounting of the bone or skull through the skin
„ B
Box or cylinder
l d restraints with
h ear pins and
d sometimes
a bite bar
„ Plaster
Pl
or resin molds
ld taken
k directly
d
l from
f
the
h animall
B. Sanghera, et al., J. of Med. Eng. and
Tech. 26 (1) (2002) 16.
M.N. Pilipuf, et al., J.
Neurosurg. 82 (6) (1995) 1082.
„ Rapid
p prototyping
p
yp g technology
gy used for
f human head
restraints
3/14
Head restraints
Types of head restraints found in literatures:
„ Rigid mounting of the bone or skull through the skin
„ B
Box or cylinder
l d restraints with
h ear pins and
d sometimes
a bite bar
„ Plaster
l
or resin molds
ld taken
k directly
d
l from
f
the
h animall
„ Rapid
p prototyping
p
yp g technology
gy used for
f human head
restraints
An animal restraint f
fabricated using
g a rapid
p prototyper
p
yp ?
3/14
Fabrication Procedures
Fabrication of an animal restraint using a rapid prototyper:
(Digital Imaging and
Communications in Medicine)
Medical CT
- DICOM
Image editing
- DICOM
Software conversion
- STL
F b i ti
Fabrication
- a reall 3D restraint
t i t
(Standard Tessellation Language )
Experiments
4/14
Fabrication Procedures
- Medical CT
„ Medical CT (0.625mm/slice, 0.47mm or 0.35mm transverse)
„ CT image storage of DICOM format
DICOM image
i
data
d t of
f the
th rats
t
The first rat (420g)
The second rat (486g )
5/14
Fabrication Procedures
- Image editing
„ IDL (Interactive Data Language) DICOM Toolkit
„ Select a common region of interest for all slices.
„ Define
D fin animal
nim l outline
utlin usin
using an
n appropriate
pp p i t grayscale
s l th
threshold
sh ld.
„ Expand the animal outline using a convolution function by 3mm
„ Combine the outlines to make a shell of the restraint
„ Rotate and orient
„ Enlarge the nose and ear holes
„ Attach support frame and labels to the restraint
6/14
Fabrication Procedures
- Image editing
DICOM images of rat head restraints
The first rat head restraint
The second rat head restraint
The Novel Field Flatteners Specifically Fabricated
for Small Animals by a Rapid Prototyper for K-Edge
Subtraction Imaging, Y. Zhu, et al.
7/14
Fabrication Procedures
- Conversion and fabrication
„ JuliusLight from Julius Software Framework
- Accurate or smooth surface modeling
„ Eden500VTM from Objet Geometries Inc.
- Vero
V
White,
Whit Transparent
T
t
STL files of the restraints
The first rat
The second rat
The second restraint on Eden500VTM
8/14
Fabrication Procedures
- Fabrication
The first rat head restraint:
Smooth surface modeling, Vero White
The second rat head restraint:
Accurate surface modeling, Transparent
9/14
Fabrication Procedures
- Experiments
„ K-edge subtraction imaging experiments at the CLS HXMA beamline
„ 0.25mm
0 25mm*28mm
28mm beam
beam, 100eV above or below the iodine K edge
„ line scan mode at 2mm/s vertical scan velocity
10/14
Results
- A live rat in lateral view
A
B
C
1 min
i llater
t
4 min
i llater
t
D
images
above
iodine
K edge
K-edge
E: (B – A)/A
5 min
i llater
t
F: (C – A)/A
G: (D – A)/A
normalized
subtracted
images
1 min later
2.7%
4 min later
2.7%
5 min later
2.8%
Results - A live rat in dorsal-ventral view
A
B
C
1 min later
4 min later
D
images
below
iodine
K edge
K-edge
E: (B – A)/A
5 min later
F: (C – A)/A
G: (D – A)/A
normalized
subtracted
images
1 min later
2.9%
4 min later
3.0%
5 min later
3.1%
12/14
Conclusions
Conclusions:
„ Rapid prototyping is a simple, fast and relatively inexpensive
method to fabricate a humane, customized animal restraint
„ The restraint holds great promise in improving the quality and
repeatability of images while reducing stress on experimental
animals
Drawback:
„ Limited tolerance to animals of different sizes
ƒ Smooth surface molding
ƒ Averaging slightly displaced DICOM images
13/14
Acknowledgements
„ V. Verge,
g B. Juurlink, N. Cox, University
y of Saskatchewan
„ T. Anderson, L. Toews, Royal University Hospital
„ R. Wilson and H. Berg, Engineering Machine Shop
„ HXMA beamline, Canadian Light Source
„ SHRF Research Group Facilitation Grant
14/14