Room: Davidson Ballroom A
Purpose: Dosimetry for small animal irradiators lacks the standardization of clinical radiotherapy practice, yet plays a central translational role in human trial design. The purpose of this work is to improve the dosimetric accuracy and consistency of animal studies by developing an independent peer review system to verify dose delivery from animal irradiators. This study focused on the development of a mouse phantom and characterization of the thermoluminescent dosimetry system for a commonly used small animal irradiator.
Methods: First, a mouse model and irradiation stand were designed with the purpose of being used in a mailable audit. Two mouse phantoms were machined from high impact polystyrene; one accommodated three thermoluminescent dosimeters (TLD) and the other an Exradin A1SL (0.053 cc) ion chamber for cross-comparison with the TLD. An acrylic irradiation stand was constructed to allow users to align the mouse phantom to the irradiatorâ€™s isocenter. Second, the mouse system was commissioned in a small animal irradiator using a 225 kVp beam. An effective tissue-air ratio was determined using the ion chamber mouse phantom. The dose rate was determined using the TG-61 â€œin-airâ€? method, along with the measured half-value layer of the beam. The response of the TLD in the mouse phantom was characterized under identical irradiation conditions.
Results: We designed a robust, user-friendly mouse phantom and foldable irradiation stand, ideal for a mail audit service. The system was commissioned at 225 kVp in a small animal irradiator. The energy correction factor for TLD in the mouse phantom was 0.731 (SD=0.003) relative to â?¶â?°Co. This factor can be applied to validate dose delivered in this model of animal irradiator.
Conclusion: We established and commissioned a methodology for independent peer review of beam output for a commonly used animal irradiator. This methodology can be used to characterize other commercially available orthovoltage irradiators.