Premium
MOSFET sensitivity dependence on integrated dose from high‐energy photon beams
Author(s) -
Tanyi James A.,
Krafft Shane P.,
Hagio Tomoe,
Fuss Martin,
Salter Bill J.
Publication year - 2008
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2815626
Subject(s) - dosimetry , reproducibility , imaging phantom , calibration , sensitivity (control systems) , dose profile , nuclear medicine , mosfet , materials science , optics , physics , voltage , medicine , mathematics , electronic engineering , transistor , statistics , quantum mechanics , engineering
The ability of a commercially available dual bias, dual MOSFET dosimetry system to measure therapeutic doses reproducibly throughout its vendor‐defined dose‐based lifetime has been evaluated by characterizing its sensitivity variation to integrated/cumulative doses from high‐energy (6 and 15 MV) photon radiotherapy beams. The variation of sensitivity as a function of total integrated dose was studied for three different dose‐per‐fraction levels; namely, 50, 200, and 1200 cGy/fraction. In standard sensitivity mode (i.e., measurements involving dose‐per‐fraction levels ≥ 100 cGy ), the response of the MOSFET system to identical irradiations increased with integrated dose for both energies investigated. Dose measurement reproducibility for the low (i.e., 50 cGy) dose fractions was within 2.1 % (if the system was calibrated before each in‐phantom measurement) and 3.1 % [if the system was calibrated prior to first use, with no intermediate calibration(s)]. Similarly, dose measurement reproducibility was between 2.2 % and 6.6 % for the conventional (i.e., 200 cGy) dose fractions and between 1.8 % and 7.9 % for escalated (i.e., 1200 cGy) dose fractions. The results of this study suggest that, due to the progressively increasing sensitivity resulting from the dual‐MOSFET design, frequent calibrations are required to achieve measurement accuracy of ≤ 3 % (within one standard deviation).