Characterization of microMOSFET detectors for in vivo dosimetry in high‐dose‐rate brachytherapy with 192Ir

Purpose The objective of this study was to characterize the Best Medical Canada microMOSFET detectors for their application in in vivo dosimetry for high‐dose‐rate brachytherapy (HDRBT) with 192Ir. We also developed a mathematical model to correct dependencies under the measurement conditions of these detectors. Methods We analyzed the linearity, reproducibility, and interdetector variability and studied the microMOSFET response dependence on temperature, source‐detector distance, and angular orientation of the receptor with respect to the source. The correction model was applied to 19 measurements corresponding to five simulated treatments in a custom phantom specifically designed for this purpose. Results The detectors (high bias applied in all measurements) showed excellent linearity up to 160 Gy. The response dependence on source‐detector distance varied by (8.65 ± 0.06)% (k = 1) for distances between 1 and 7 cm, and the variation with temperature was (2.24 ± 0.05)% (k = 1) between 294 and 310 K. The response difference due to angular dependence can reach (10.3 ± 1.3)% (k = 1). For the set of measurements analyzed, regarding angular dependences, the mean difference between administered and measured doses was −4.17% (standard deviation of 3.4%); after application of the proposed correction model, the mean difference was −0.1% (standard deviation of 2.2%). For the treatments analyzed, the average difference between calculations and measures was 4.7% when only the calibration coefficient was used, but it is reduced to 0.9% when the correction model is applied. Conclusion Important response dependencies of microMOSFET detectors used for in vivo dosimetry in HDRBT treatments, especially the angular dependence, can be adequately characterized by a correction model that increases the accuracy of this system in clinical applications.