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Purpose: An implantable metal-oxide semiconductor field effect transistors-based dosimeter has recently been developed for the in vivo monitoring of hypofractionated radiotherapy. This DVS-HFT dosimeter is designed for fraction sizes of 340-950 cGy and can also be used for bis in die fraction monitoring. The current work reports on the testing and evaluation of this dosimeter, including both its basic characteristics as well as its performance during simulated clinical treatment plans. Methods: The authors tested the dose rate dependence of this dosimeter (300 MU/min versus 600 MU/min), the treatment time dependence (4 min per treatment versus up to 60 min per treatment), and the dose and energy dependence (6 and 18 MV irradiations of 700-900 cGy per fraction). Additionally, they irradiated the detectors in-phantom with breast and prostate hypofractionated treatments. Results: The detectors showed no significant dose rate, treatment time, energy, or dose dependence. Furthermore, the detectors were found to perform within manufacturer tolerances for all hypofractionated treatments examined, accurately reporting the measured dose (average disagreement of - 0.65%). Conclusions: These dosimeters appear well suited for in vivo monitoring of hypofractionated radiotherapy doses, and thereby, have the potential to improve patient care.

Purpose: Evaluate the performance of an implantable MOSFETdosimeter designed for hypo‐fractionated protocols. Method and Materials: The DVS® implantable dosimeter has been developed for use with external beam radiotherapy. A new version is currently under development for use with hypo‐fractionated protocols (DVS‐HFT*). This dosimeter is pre‐calibrated for use at body temperature in a dose per fraction range of 340–1200 cGy. The dosimeter response was evaluated in a water phantom at 37°C to validate the accuracy as a function of dose. Since delivery times for high dose fractions can vary, a study of the response as a function of treatment time was performed. In addition, dose rate dependency for high doses was evaluated. Final dosimeter accuracy was validated by delivering simulated hypo‐fractionated treatments on a body phantom at 37 °C. Two dosimeters each (total six) were irradiated inside the phantom with a breast BID plan at 340 cGy per fraction (10 fx), two prostate IMRT plans at 700 cGy per fraction (5 fx) using 6 MV and 18 MV. Results: The dosimeter had minimum dependency on dose fraction size from 340 to 1200 cGy. Phantom testing found a response accuracy of