Scintillation dosimetry for FLASH radiotherapy

The use of ultra-high dose rate (UHDR) beams for radiotherapy treatments is currently of great interest, as multiple experimental findings show that they may elicit the so-called FLASH effect, an increased sparing of normal tissues while maintaining unaltered tumour control. Dosimetry and beam monitoring in FLASH radiotherapy require a paradigm shift in both instrumentation and methodology compared to conventional radiotherapy, given the specific characteristics of UHDR beams. In this scenario, scintillation detectors have emerged as a valid dosimetric tool, and tens of studies have been published in the past few years. In this review paper, we first recall the general properties of scintillators (e.g., scintillator types, available detector geometries, readout systems, and experimental configurations) and discuss the challenges that arise in the context of scintillation dosimetry, with specific reference to FLASH radiotherapy (e.g., linearity and radiation damage). We then provide a comprehensive overview of the current state of research and development in FLASH scintillation dosimetry, focusing on its most critical aspects. The manuscript concludes with a short comparison to other available technologies and a discussion of the key findings to date and future perspectives.