Small Animal Conformal Radiation Therapy Device
We are developing a Small Animal Conformal Radiation Therapy Device (SACTRD)
that will provide a degree of geometric/anatomic targeting comparable to
what is achievable in current clinical radiotherapy practice to promote
translational research in radiation oncology and radiation sciences. The
SACRTD will integrate 3D-conformal radiation therapy delivery with Cone Beam
Computerized Tomography (CBCT) imaging for registration, localization, tumor
and normal tissue segmentation, 3D dose computation/optimization and
advanced treatment planning tools.
– On-board CBCT imaging, 0.5mm voxel
– Adequate dose output, ~ 200 cGy/min
– Dose localization to < 1 mm
– Setup/repositioning ~ 0.5 mm
– Advanced treatment planning tools,
calculation and verification
The X-ray tube has
two foci, a small focus of 0.4 mm, 640 W, which can be coupled with a
collimating cone for irradiation field sizes ≤ 4 mm x 4 mm, and a large
focus of 3.0 mm, 3000 W, which for field sizes of up to 60 mm x 60 mm with
appropriate collimators. The maximum dose rate at 1 meter from the tube is ~
13 Sv/hr at maximum tube voltage and maximum anode dissipation, and produces
< 10 mSv/hr of leakage radiation.
The system is housed in a 6
x 6 x 6 ft3 enclosure constructed out of a steel frame and lead
blankets. The X-ray source is mounted ~40 inch from the floor. The
door-on-a-wheel has a magnetic lock with an emergency switch to open from
inside for safety. A door interlock (contact switch) ensures that no
beam-on is possible when door is open. The structure holding the X-ray tube
and other components is constructed from modular framing system (80/20 Inc).
The shielding of SACRTD meets/exceeds the
safety requirements of NCRP Report 49, which is good for sources up to 500
kV. The primary beam is shielded by 1 inch of lead equivalent or more and
secondary and leakage radiations are shielded by ½ in of lead equivalent
(two layers of 10 lb/ft2 lead blankets)
Beam Delivery System With Robotic Positioning:
Viper 6-Axis Robot
CT System with Robotic Positioning of Animal:
The cone beam CT
image will be acquired with a digital X-ray imager using the same X-ray tube
used for therapy but operated at a lower energy (~ 80-120 kVp). The animal,
positioned at isocenter, will be rotated by the robot. Robot motion, X-ray
activation and data acquisition by the imager will be under
computer-control. Planar radiographic projections of an animal image are
recorded by the digital X-ray imager aSi flat panel detector. These 2D
projections will be processed to reconstruct a 3D volumetric image.
Rotating animal platform using a robotic arm with 6 degree of
Imager: aSi Flat panel digital X-ray detector
80-120 kVp, dose ~5 cGy
for Conformal Radiation Delivery:
efforts (2008) are focused, dosimetric characterization of the
X-ray beam at various energies, installation and implementation of the
imaging system and software, development of a treatment planning platform,
and controlling of the robotic animal positioning system, the imaging system
and the X-ray tube from the one computer.
Arkansas Biomedical Institute and the Arkansas Master Tobacco Settlement
The Central Arkansas Radiation Therapy Institute (CARTI).
Department of Radiation Oncology.
We are grateful
for collaboration with John Hopkins University.