Pulse-resolved real-time dosimetry in FLASH radiotherapy using Ge-doped silica fiber scintillators

We present a time-resolved evaluation of a Ge-doped silica fiber scintillator under ultra-high dose-rate (FLASH) radiotherapy conditions delivered by a 6 MeV clinical linear accelerator capable of achieving instantaneous dose rates up to 500 kGy/s. This study aimed to assess the scintillator's ability to accurately measure such extreme radiation conditions. While successful signal acquisition was achieved across a range of pulse repetition frequencies (PRFs), saturation effects—including signal plateauing and decay overlap—were observed at PRFs above 200 Hz, leading to baseline elevation and reduced peak resolution. Nevertheless, the dose–response remained approximately linear, with minor degradation in correlation at the highest PRFs. An iterative deconvolution technique mitigated pile-up artifacts and restored signal fidelity. These findings demonstrate both the potential and current limitations of Ge-doped fiber dosimeters for real-time FLASH dosimetry, underscoring the need for correction strategies to ensure accurate dose measurements at ultra-high delivery rates.