In vivo measurement of radiation dose during radiotherapy in breast cancer patients using MOSFET dosimeter

Objective The purpose of the study was to observe and analysis the actual dosage of patients with breast cancer using metal oxide semiconductor field effect transistor (MOSFET) detector.Methods First, Phantom measurements were performed to investigate dose distribution in the area of the junction in a half-field matching method and the influence of factors related to the accelerator. In vivo dose measurements were performed for patients with breast cancer to investigate the skin dose and the junction of supraclavicular-axillary field and tangential field in 6 MV X-ray beams. Results Phantom measurements showed that the relative deviation in the junction were within + 3％, and the dose distributions in the junction area depended on the matching field direction (x or y). In vivo measurement of tangential region for patients showed that, the maximum dose deviation between measurement and calculation was -30. 39％,the minimum deviation was - 18. 85％, the average dose deviation was -24. 76％. The dose deviation of tangential fields for patients with breast-conserving surgery was larger than that patients with radical surgery (t =2. 40 ,P＜0. 05), while dose deviation of supraclavicular-axillary fields was not significantly different. The average values of 15 fraction in the junction area showed more stable than one individual measurement.Conclusions It is important to real-time, in vivo measurement of radiation dose during radiotherapy in patients with breast cancer, and change treatment plan in time, to ensure the accuracy of target dose. Key words: Metal oxide semiconductor field effect transistor detector;  Dosimetry;  Adjacent half-fields;  Phantom;  Breast neoplasm