Compact and Real-Time Radiation Dosimeter Using Silicon Photomultipliers for In Vivo Dosimetry in Radiation Therapy

Existing dosimeters for radiation therapy are typically large, and their performance in in vivo system applications has not been assessed. This study develops a compact real-time dosimeter using silicon photomultipliers, plastic scintillators, and optical fibers and evaluates its in vivo applicability for radiation therapy. Dose calibration, dose-rate dependency and linearity, and short-term repeatability tests were conducted using solid water phantoms and bolus materials, and in vivo dosimetry was performed using an in-house phantom. The characterization evaluation results showed high linearity, with a coefficient of determination of 0.9995 for dose rates of 100-600 monitoring units (MU)/min, confirming an error rate within 2% when converted to dosage. In the short-term repeatability tests, the dosimeter exhibited good characteristics, with relative standard deviation (RSD) values lower than 2% for each beam delivery and an RSD value of 0.03% over ten beam deliveries. Dose measurements using the phantom indicated an average error rate of 3.83% compared to the values calculated using the treatment planning system. These results demonstrate a performance comparable to that of commercial metal-oxide-semiconductor field-effect transistors and plastic scintillator-based dosimeters. Based on these findings, the developed dosimeter has significant potential for in vivo radiation therapy applications.