Development of a micro-computed tomography-based image-guided conformal radiotherapy system for small animals.
OBJECTIVE
To report on the physical aspects of a system in which radiotherapy functionality was added to a micro-computed tomography (microCT) scanner, to evaluate the accuracy of this instrument, and to and demonstrate the application of this technology for irradiating tumors growing within the lungs of mice.


METHODS
A GE eXplore RS120 microCT scanner was modified by the addition of a two-dimensional subject translation stage and a variable aperture collimator. Quality assurance protocols for these devices, including measurement of translation stage positioning accuracy, collimator aperture accuracy, and collimator alignment with the X-ray beam, were devised. Use of this system for image-guided radiotherapy was assessed by irradiation of a solid water phantom as well as of two mice bearing spontaneous MYC-induced lung tumors. Radiation damage was assessed ex vivo by immunohistochemical detection of gammaH2AX foci.


RESULTS
The positioning error of the translation stage was found to be <0.05 mm, whereas after alignment of the collimator with the X-ray axis through adjustment of its displacement and rotation, the collimator aperture error was <0.1 mm measured at isocenter. Computed tomography image-guided treatment of a solid water phantom demonstrated target localization accuracy to within 0.1 mm. Gamma-H2AX foci were detected within irradiated lung tumors in mice, with contralateral lung tissue displaying background staining.


CONCLUSIONS
Addition of radiotherapy functionality to a microCT scanner is an effective means of introducing image-guided radiation treatments into the preclinical setting. This approach has been shown to facilitate small-animal conformal radiotherapy while leveraging existing technology.
Zhou
Hu
H
Department of Radiation Oncology, Stanford University, Stanford, CA 94305-5847, USA.
Rodriguez
Manuel
M
van den Haak
Fred
F
Nelson
Geoffrey
G
Jogani
Rahil
R
Xu
Jiali
J
Zhu
Xinzhi
X
Xian
Yongjiang
Y
Tran
Phuoc T
PT
Felsher
Dean W
DW
Keall
Paul J
PJ
Graves
Edward E
EE
D000818:Animals; D002138:Calibration; D004867:Equipment Design / Q000379:methods; D008175:Lung Neoplasms / Q000532:radiotherapy*; D051379:Mice; D008822:Mice, Transgenic; D008838:Microcomputers; D019047:Phantoms, Imaging; D011786:Quality Control; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000379:methods
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