Development and application of in-vivo dose and time-resolved measurements for clinical application of ultra-high dose rate radiotherapy

Background and PurposeUltra-high-dose-rate (UHDR) radiotherapy (RT) has emerged as a promising technique to widen the therapeutic window.However, clinical implementation is critically dependent on standardized dosimetry systems.This study reports on the integration of passive and active detectors for in-vivo dose monitoring in a clinical setting. Materials and MethodsFour detector systems were evaluated for patient treatments with UHDR at a modified C-arm linear accelerator (linac) (9 MeV, dose per pulse 1.08 Gy, average dose rate 216 Gy/s): two passive systems -optically stimulated luminescence detectors (OSLDs) and radiochromic films -and two active systems -a scintillator and a diamond detector.The detectors were positioned on a dedicated 3D-printed mount or the patient skin to measure integral dose and time-resolved parameters.OSLDs were calibrated against a reference ion chamber and validated under varying conditions.Scintillator and diamond detectors recorded pulse-topulse and intra-pulse stability, respectively. ResultsOSLDs provided reproducible dose reporting within 5%, with precision improved through averaging multiple chips.The pulse-to-pulse stability measured with the scintillator was in agreement with the diamond detector measurements within 1%.The diamond detector resolved intra-pulse stability and identified instabilities in case of poor beam tuning. ConclusionsThe combined use of OSLDs, scintillator, diamond, and film detectors enabled robust and time-resolved recording of UHDR RT in a clinical trial setting.While resource-intensive, this approach ensured redundancy and precision, providing a feasible strategy for early clinical adoption.