Metrology for advanced radiotherapy using particle beams with ultra-high dose rates.

Dosimetry of ultra-high dose-rate (UHDR) beams is one of the critical components which is required for safe implementation of FLASH radiotherapy into clinical practice. In the past years several national and international programmes have emerged with the aim to address some of the needs that are required for translation of this modality to clinics. These involve the establishment of dosimetry standards as well as the validation of protocols and dosimetry procedures. This review provides an overview of recent developments in the field of dosimetry for FLASH radiotherapy, with particular focus on primary and secondary standard instruments, and provides a brief outlook on the future work which is required to enable clinical implementation of FLASH radiotherapy.