Development of Photodiode-Based IOT Detector for Area Monitoring in Brachytherapy Rooms

A monitoring system was developed to measure the ambient dose equivalent rate H*(10) in High Dose Rate (HDR) brachytherapy rooms. For this research work, HDR brachytherapy implements radioac- tive sources of Ir-192 with a maximum activity of 10 Ci. The detector consists of an array of three VBPW34FAS p-i-n photodiodes, which detect incident gamma photons, and electronic stages that condition and shape the output current. Shaped pulses are integrated in a capacitor, producing a voltage value that correlates with H*(10). The instrument has a detection range from 0.03 to 715 mSv/h, with an expanded uncertainty of 2.36%. It was calibrated using a reference Geiger-Mu¨ller dosimeter, with measurements differing by less than 2%. The system has a Wi-Fi connection to send data to ThingSpeak for display and storage, providing a historical record of H*(10) over time for dosimetric quality control tests, in compliance with radiation protection requirements.