Measurement of dose with metal oxide semi-conductor field effect transistor in radiotherapy

Objective: To study the measurement of the radiation doses of patient using MOSFET with photon beam in radiotherapy. Methods: The experiments of reproducibility, non-linearity dose response, dependence of dose rate, and reproducibility at different dose levels were carried out with 6 MV X-ray beam by using MOSFET. According to the need in clinical treatment, the doses were selected depending on the field size, distance of source to skin, angle of incidence, energy response, wedge angle, and block and tray. The corresponding calibration factors were calculated. The doses of the pelvis, head and neck were validated with Alderson phantom and MOSFET. 42 cases of patients were choosed to evaluate the difference between MOSFET measured dose and TPS calculated dose. Results: 644 dose points were measured with MOSFET, including 374 points for abdomen radiotherapy and 270 for head and neck radiotherapy. The relative deviation was within ±5% both for 78.3% of abdomen radiotherapy and for 85.7% of head and neck radiotherapy. Conclusions: MOSFET is real-time and convenient to measure the radiotherapy doses of patients. It can be used as a method for quality control and assurance of clinical radiotherapy. (authors)