Abstract
Introduction: FLASH radiotherapy is based on delivering an ultra-high dose of ionizing radiation in a very short time, which allows for the enhanced protection of healthy tissues and the effective destruction of tumour tissues. The paper presents experimental verification of the applicability of the intraoperative electron radiotherapy (IOERT) accelerator to obtain electron beams with ultra-high dose rates. The results of electron beam dosimetric measurements were compared with simulations to verify the parameters of the electron beams obtained in FLASH mode.
Material and Methods: The IOERT AQURE accelerator is designed and manufactured at the National Centre for Nuclear Research. The device provides electron beams with energies in the energy range of 4-12 MeV. The accelerator was recently upgraded to deliver ultra-high-dose rates (FLASH). The emitted electron beams were verified by percentage dose depth (PDD) and beam profile measurements using Gafchromic EBT-XD films. The measurement results were compared with Monte Carlo simulations performed using the Geant4 application.
Results: Conventional and FLASH electron beam parameters, i.e. depths of doses, most probable beam energies at the phantom surface, and average beam energies at the phantom surface were determined experimentally for the upgraded IOERT accelerator for 6 MeV and 9 MeV. The results of dose measurements showed that the accelerator can provide electron beams with homogeneous and symmetrical fields with dose rates up to 300 Gy/s ± 6 Gy/s, for an electron beam at a nominal energy of 6 MeV, and up to 440 Gy/s ± 9 Gy/s at a nominal energy of 9 MeV. A comparison of measured and simulated PDDs and dose profiles for FLASH beams showed good agreement (no worse than 90%) under the gamma index of 3%/3 mm.
Conclusions: The results obtained confirm that the upgraded intraoperative accelerator can be used in planned, pre-clinical radiobiology experiments in both conventional and ultra-high dose rate (FLASH-RT) modes.