title: Image-Guided Radiotherapy Using a Modified Industrial Micro-CT for Preclinical Applications.
abstract: OBJECTIVE
  Although radiotherapy is a key component of cancer treatment, its implementation into pre-clinical in vivo models with relatively small target volumes is frequently omitted either due to technical complexity or expected side effects hampering long-term observational studies. We here demonstrate how an affordable industrial micro-CT can be converted into a small animal IGRT device at very low costs. We also demonstrate the proof of principle for the case of partial brain irradiation of mice carrying orthotopic glioblastoma implants.
  
  
  METHODS
  A commercially available micro-CT originally designed for non-destructive material analysis was used. It consists of a CNC manipulator, a transmission X-ray tube (10-160 kV) and a flat-panel detector, which was used together with custom-made steel collimators (1-5 mm aperture size). For radiation field characterization, an ionization chamber, water-equivalent slab phantoms and radiochromic films were used. A treatment planning tool was implemented using a C++ application. For proof of principle, NOD/SCID/γc(-/-) mice were orthotopically implanted with U87MG high-grade glioma cells and irradiated using the novel setup.
  
  
  RESULTS
  The overall symmetry of the radiation field at 150 kV was 1.04 ± 0.02%. The flatness was 4.99 ± 0.63% and the penumbra widths were between 0.14 mm and 0.51 mm. The full width at half maximum (FWHM) ranged from 1.97 to 9.99 mm depending on the collimator aperture size. The dose depth curve along the central axis followed a typical shape of keV photons. Dose rates measured were 10.7 mGy/s in 1 mm and 7.6 mGy/s in 5 mm depth (5 mm collimator aperture size). Treatment of mice with a single dose of 10 Gy was tolerated well and resulted in central tumor necrosis consistent with therapeutic efficacy.
  
  
  CONCLUSIONS
  A conventional industrial micro-CT can be easily modified to allow effective small animal IGRT even of critical target volumes such as the brain.
authors.affiliation: Medical Radiation Physics/Radiation Protection, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany; Department of Radiation Oncology, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Manuela C
authors.initials: MC
authors.lastname: Felix
authors.affiliation: Department of Radiation Oncology, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Fleckenstein
authors.affiliation: Department of Neuroradiology, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Kirschner
authors.affiliation: Department of Radiation Oncology, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Linda
authors.initials: L
authors.lastname: Hartmann
authors.affiliation: Department of Radiation Oncology, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Frederik
authors.initials: F
authors.lastname: Wenz
authors.affiliation: Department of Neuroradiology, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany; Department of Diagnostic and Interventional Neuroradiology, University Hospital Aachen, Aachen, Germany.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Brockmann
authors.affiliation: Medical Radiation Physics/Radiation Protection, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany; Department of Radiation Oncology, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Glatting
authors.affiliation: Department of Radiation Oncology, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Frank A
authors.initials: FA
authors.lastname: Giordano
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000473:pathology / Q000532:radiotherapy; D051379:Mice; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D015203:Reproducibility of Results; D055114:X-Ray Microtomography / Q000379:methods*