SU‐E‐T‐317: MOSFET Assessment of Radiation Dose Delivered to Mice Using the Small Animal Radiation Research Platform (SARRP)

Abstract

Purpose: MOSFETS were employed in this study for in situ assessment of radiation dose delivered by the Small Animal Radiation Research Platform (SARRP) to mouse anatomical target volumes: brain, left kidney, left lung, liver, pancreas and prostate. Method and Materials:MOSFET detectors were calibrated with conversion factors (CF) determined for each MOSFET as a function of depth in tissue equivalent material. Calibrated MOSFET was surgically implanted post‐euthanasia into the mouse target volume, with minimal organ disruption. Using CBCT imaging and robotic motion, the mouse was then positioned with implanted MOSFET at the isocenter of the SARRP. The depth of the MOSFET from the CBCT image and corresponding CF were used in the SARRP dose calculation program to calculate the target dose for 220 kVp and 13 mA, without heterogeneity correction. Irradiations were conducted using a 0.15 cm copper filter. Three readings per MOSFET were obtained for each organ of three euthanized male mice. The measured dose was determined by averaging the MOSFET readings for that organ. The percentage difference between the measured and calculated dose was determined. Results: The results showed differences between the calculated and measured dose of between: +1.2 to 4.6 %, −3.3 to +4.8 %, +0.9 to +5.1 %, −5.9 to +2.5 %, ‐2.3 to +1.0 %, and −4.3 to +1.4 %, for the left kidney, liver, pancreas, prostate, left lung, and brain, respectively. Conclusions: The study indicates that, for 220 kVp x‐rays, the radiation dose delivered by the SARRP to characteristic target volumes in mice is within 6% of the calculated dose. The results provide a useful assessment of the need for tissue heterogeneity corrections in SARRP dose calculations for clinically relevant tumor model sites. The work also demonstrates the feasibility of using MOSFET dosimeters for in situ assessment of SARRP radiation dose delivery.