Time-resolved dosimetry of pulsed photon beams for radiotherapy based on diamond detector

The widespread diffusion of precision radiotherapy techniques, geared toward the release of larger dose gradients in shorter time frames, is leading to new challenges in dosimetry. Accurate dose measurements are essential to check for beam anomalies and inaccuracies to ensure treatment efficacy and patient safety during radiotherapy. This work describes the main features of a diamond dosimeter coupled to an extremely compact front-end electronics. The detection system was tested under the X-ray pulses generated by a medical LINAC for both the 6 MV and the 18 MV accelerating voltages. Located in the LINAC's bunker, it eliminates the need for a long cable connection between the detector and the electronics, detrimental for the system response speed. Signal acquisition was performed synchronously with the impinging X-ray pulses with a sampling period as low as 20 μs, allowing for a real-time beam monitoring. The dosimeter demonstrated a very good stability despite the high value of the absorbed dose during the performed experiments (~100 Gy). The measured dose-per-pulse values of 278 μGy and 556 μGy at 6 MV and 18 MV, respectively, are in excellent agreement with the nominal values expected for the LINAC apparatus used for the tests. In addition to single-pulse measurements, fundamental for dynamic radiotherapy, the proposed system also allows for the calculation of both the total collected charge and the photocurrent generated by the detector. In this regard, despite the compactness, it demonstrates its effectiveness as a tool for source diagnostics in terms of both beam intensity and emission timing.