TIME-RESOLVED PROTON BEAM DOSIMETRY FOR ULTRA-HIGH DOSE-RATE CANCER THERAPY (FLASH)

A new radiotherapy modality, known as FLASH, is a potential breakthrough in cancer care as it features a reduced damage to healthy tissues, resulting in the enhancement of the clinical benefit. FLASH irradiations are characterized by ultra-high dose-rates (>40 Gy/s) delivered in fractions of a second. This represents a challenge in terms of beam diagnostics and dosimetry, as detectors used in conventional radiotherapy saturate or they are too slow for the FLASH regime. In view of the FLASH clinical translation, the development of new dosimeters is fundamental. Along this line, a research project is ongoing at the University of Bern aiming at setting-up new beam monitors and dosimeters for FLASH. The proposed detection system features millimeter scintillators coupled to optical fibers, transporting light pulses to a fast photodetector, readout by high bandwidth digitizers. First prototypes were exposed to the 18 MeV proton beam at the Bern medical cyclotron. The new detectors have been found to be linear in the range up to 780 Gy/s, with a maximum time resolution of 100 ns. These characteristics are promising for the development of a new class of detectors for FLASH radiotherapy.