• flash radiotherapy
• geant4
• dosimetry
• scintillators
• electrons

Technological advances have improved radiotherapy techniques, becoming more precise and safer. However, radiotherapy still has risks, ranging from skin necrosis to significant healthy tissue damage, which limit its applicability. The new approach to radiation treatment with FLASH radiotherapy, consisting in ultra-high dose rate administration of the whole dose in fractions of a second, has shown promising results in recent studies, where an amplified healthy tissue sparing effect was observed with the same cancer tissue kill efficacy. So far, electron FLASH dosimetry has been performed with dose rate independent dosimeters, since conventional online instruments in FLASH conditions suffer from significant uncorrectable saturation, making them unusable. However, there is evidence that scintillators seem to have less saturation for high dose per pulse values. In this master's thesis, a novel method for online electron FLASH radiotherapy dosimetry, based on integrator-mode scintillator detectors, is investigated.
Two dosimeters, designed at the INFN in Pisa, are studied. One is a plastic scintillator, the other is based on a LYSO crystal. I designed a GEANT4 Monte Carlo code to account for medium-equivalence corrections, and Python scripts for data analysis. Experimental measurements in FLASH conditions conducted with the ElectronFlash electron beam accelerator at the Sordina IORT Technologies S.p.A installation. By varying the dose per pulse in FLASH conditions, saturation has been observed at 12.5 Gy/pulse, which is on the high-end of dose per pulse values used in radiobiological studies. The investigations allow to conclude that the use of scintillators are a promising solution for online electron FLASH dosimetry.