Development of a dose-rate dosimeter using a silicon photodiode for a medical linear accelerator in a 10 MV flattening filter-free mode.

This article focuses on the development and evaluation of a dose-rate dosimeter using a silicon photodiode (Si-PD) sensor to measure instantaneous dose rates and depth dependence in radiotherapy with a commercially available medical linear accelerator (medical linac). The Si-PD dosimeter, incorporating a complementary metal-oxide semiconductor (CMOS) operational amplifier, resistor, capacitor, and a copper filter for energy correction, demonstrated dose-rate measurements up to approximately 0.6 Gy/s and showed peak voltage variations corresponding to instantaneous dose rates at different depths in a solid–water phantom. While the dosimeter’s measurements correlated well with a reference semiconductor dosimeter for x-ray tube calibration, limitations were noted in pulse detection accuracy and sampling speed during medical linac irradiation, indicating the need for further improvements. The study highlights the potential of the Si-PD dosimeter as a compact, inexpensive tool for dose-rate monitoring in radiotherapy, including applications related to emerging ultra-high dose rate ("FLASH") treatments.