title: Development of a micro-computed tomography-based image-guided conformal radiotherapy system for small animals.
abstract: 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.
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, CA 94305-5847, USA.
authors.forename: Hu
authors.initials: H
authors.lastname: Zhou
authors.forename: Manuel
authors.initials: M
authors.lastname: Rodriguez
authors.forename: Fred
authors.initials: F
authors.lastname: van den Haak
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Nelson
authors.forename: Rahil
authors.initials: R
authors.lastname: Jogani
authors.forename: Jiali
authors.initials: J
authors.lastname: Xu
authors.forename: Xinzhi
authors.initials: X
authors.lastname: Zhu
authors.forename: Yongjiang
authors.initials: Y
authors.lastname: Xian
authors.forename: Phuoc T
authors.initials: PT
authors.lastname: Tran
authors.forename: Dean W
authors.initials: DW
authors.lastname: Felsher
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Keall
authors.forename: Edward E
authors.initials: EE
authors.lastname: Graves
mesh_terms: 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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