Commissioning and performance assessment of diodes and MOSFETs in in-vivo dosimetry for external beam radiation therapy.

The precision of radiation therapy treatment depends on several calibration and quality assurance processes. In-vivo dosimetry (IVD) is used in external beam radiotherapy to evaluate the delivered versus planned dose as a patient-specific quality assurance verification procedure. This study aimed at assessing the performance of diodes (EDP-103G and EDP-203G) and metal oxide semiconductor field-effect transistors (MOSFETs) and corresponding correction factors followed by IVD evaluation in different treatment configurations. Linearity, stability, gantry angle, field size, and source-to-subject distance (SSD) were assessed across various photon energies, with correction factors determined. To minimize patient movement uncertainty, the study utilized the Alderson Rando phantom to replicate clinical setups, comparing diode and MOSFET dose readings to treatment planning system (TPS) doses. Diodes and MOSFETs were evaluated across different photon energy levels for brain, chest, and pelvis planning sites. Diodes and MOSFETs demonstrated good stability and linearity at the different utilized photon beams. Data analysis showed that MOSFETs had a slightly higher sensitivity compared to diodes in gantry angle, field size and SSD corrections. Regarding the validation process after applying the correction factors, dose variations between diode readings and TPS doses were found to be 1.89%, 1.58%, and 6.72% for brain, breast, and pelvis, respectively. In contrast, MOSFET readings were 2.40% for brain, 2.03% for chest, and 2.03% for pelvis. It is concluded that, while diode and MOSFET dosimeters both allowed for accurate patient dose measurements, for different anatomical sites, MOSFETs demonstrated better performance for the pelvis compared to diodes.