Author ORCID Identifier
0000-0002-0121-9579
Date of Graduation
8-2018
Document Type
Thesis (MS)
Program Affiliation
Medical Physics
Degree Name
Masters of Science (MS)
Advisor/Committee Chair
Rebecca M Howell, Ph.D.
Committee Member
David S Followill, Ph.D.
Committee Member
Sunil Krishnan, M.D.
Committee Member
Stephen F Kry, Ph.D.
Committee Member
Mohammad R Salehpour, Ph.D.
Committee Member
Ramesh C Tailor, Ph.D.
Abstract
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 was 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.
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 (Standard Imaging, Middleton, WI) for cross-comparison with the TLD. An acrylic irradiation stand was constructed to allow users to align the mouse phantom to the irradiator’s isocenter. Second, the mouse system was commissioned in a small animal irradiator using a 225 kVp beam. A pseudo tissue-air ratio was determined using the ion chamber mouse phantom. The dose rate was determined using the TG-61 “in-air” 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. Lastly, the commissioned mouse system was mailed to two institutions to verify feasibility of the service.
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 0.792 (SD=0.006) relative to 60Co. This factor can be applied to validate dose delivered in this model of animal irradiator. The feasibility of the independent peer review system was demonstrated by verifying beam output and small animal dosimetry for two institutions.
We established and commissioned a methodology for independent peer review of mouse dosimetry for a commonly used animal irradiator. This methodology can be used to characterize other commercially available orthovoltage irradiators.
Keywords
mail audit, independent peer review, dosimetry audit, orthovoltage, thermoluminescent dosimetry, phantoms, small animal irradiators