SU-FF-T-192: DVS MOSFET Dosimeter Response to Kilovoltage Radiation

Abstract

Purpose: To determine the dose response of implantable DVS MOSFET dosimeters to kilovoltage x‐ray radiation compared to the response to irradiation from a 60 Co source. Method and Materials: Sicel Technologies, Inc. has developed a Dose Verification System (DVS®), using implantable MOSFET dosimeters that are read telemetrically by an inductively coupled antenna. Three Virtual Water™ phantom cassettes, each containing four DVS dosimeters, were irradiated in a Virtual Water phantom with a 60 Co source for five doses of 200 cGy. These were used as controls to compare to a fourth cassette that was similarly irradiated by the 60 Co source before it was exposed to kV energy at NIST‐equivalent beam qualities of M80, L100, M100, M120, and M150. The dose delivered was determined following TG‐61 protocol (in‐phantom method at 2 cm depth), substituting Virtual Water for liquid water. Following the x‐ray exposures, the cassette was exposed again to 60 Co to confirm device stability. Results: Before correcting for temperature, energy, and isotropy, the 60 Co cassettes demonstrated a slight and consistent under‐response. After appropriate scaling, the overall ratio of corrected dose measured to dose delivered was 1.002 ± 0.004. The dosimeters irradiated with the kV beams, however, exhibited an over‐response. The overall ratio of corrected dose measured to dose delivered for the kV beams was 2.428 ± 0.043, whereas the same cassette demonstrated nearly the same response to the 60 Co source as the other three cassettes, with a ratio of corrected dose measured to dose delivered of 0.9755 ± 0.0113. Conclusion: This data shows the DVS dose response for the examined kV beams at 2 cm depth is ∼2–3 times greater than the response at MeV energies from the 60 Co source due to the shift in dominance from Compton to photoelectric events. Conflict of Interest: Funding for this research was provided by Sicel Technologies, Inc.