title: Toward an organ based dose prescription method for the improved accuracy of murine dose in orthovoltage x-ray irradiators.
abstract: OBJECTIVE
  Accurate dosimetry is essential when irradiating mice to ensure that functional and molecular endpoints are well understood for the radiation dose delivered. Conventional methods of prescribing dose in mice involve the use of a single dose rate measurement and assume a uniform average dose throughout all organs of the entire mouse. Here, the authors report the individual average organ dose values for the irradiation of a 12, 23, and 33 g mouse on a 320 kVp x-ray irradiator and calculate the resulting error from using conventional dose prescription methods.
  
  
  METHODS
  Organ doses were simulated in the Geant4 application for tomographic emission toolkit using the MOBY mouse whole-body phantom. Dosimetry was performed for three beams utilizing filters A (1.65 mm Al), B (2.0 mm Al), and C (0.1 mm Cu + 2.5 mm Al), respectively. In addition, simulated x-ray spectra were validated with physical half-value layer measurements.
  
  
  RESULTS
  Average doses in soft-tissue organs were found to vary by as much as 23%-32% depending on the filter. Compared to filters A and B, filter C provided the hardest beam and had the lowest variation in soft-tissue average organ doses across all mouse sizes, with a difference of 23% for the median mouse size of 23 g.
  
  
  CONCLUSIONS
  This work suggests a new dose prescription method in small animal dosimetry: it presents a departure from the conventional approach of assigninga single dose value for irradiation of mice to a more comprehensive approach of characterizing individual organ doses to minimize the error and uncertainty. In human radiation therapy, clinical treatment planning establishes the target dose as well as the dose distribution, however, this has generally not been done in small animal research. These results suggest that organ dose errors will be minimized by calibrating the dose rates for all filters, and using different dose rates for different organs.
authors.affiliation: Medical Physics Graduate Program, Duke University Medical Center, Durham, North Carolina 27705.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Belley
authors.affiliation: Medical Physics Graduate Program, Duke University Medical Center, Durham, North Carolina 27705.
authors.forename: Chu
authors.initials: C
authors.lastname: Wang
authors.affiliation: Duke Radiation Dosimetry Laboratory, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: Giao
authors.initials: G
authors.lastname: Nguyen
authors.affiliation: Duke Radiation Dosimetry Laboratory, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: Rathnayaka
authors.initials: R
authors.lastname: Gunasingha
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710 and Department of Immunology, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: Nelson J
authors.initials: NJ
authors.lastname: Chao
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: Benny J
authors.initials: BJ
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Dewhirst
authors.affiliation: Duke Radiation Dosimetry Laboratory, Duke University Medical Center, Durham, North Carolina 27710; Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710; and Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: Terry T
authors.initials: TT
authors.lastname: Yoshizumi
mesh_terms: D000465:Algorithms; D000818:Animals; D002138:Calibration; D003198:Computer Simulation; D051379:Mice; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D015203:Reproducibility of Results; D012119:Respiration; D014057:Tomography, X-Ray Computed / Q000379:methods; D014965:X-Rays