Verification of real-time dosimetry of ultra-high dose rate beams at AQURE FLASH RT on the sample surface

Introduction: FLASH radiotherapy involves delivering a dose of ultra-high-dose-rate ionising radiation (>40 Gy/s) in less than 200 ms, resulting in sparing healthy tissue and effectively destroying cancerous tissue. This article presents a preliminary verification of the feasibility of using real-time internal dosimetry at the sample surface to measure doses generated by the AQURE FLASH RT accelerator dedicated to FLASH radiotherapy studies.

Material and Methods: The AQURE FLASH RT emits a 6 and 9 MeV electron beam with a dose rate higher than 40 Gy/s. The real-time dosimetry system to measure doses on the sample surface was implemented into the accelerator and consists of inductive sensors in which the moving electron charge induces a voltage in the secondary toroidal winding. The internal dosimetric system was preliminarily calibrated for single pulse irradiations using passive dosimetry methods, i.e. film and alanine dosimetry.

Results: The study showed that there was no effect of the tested dosimetry system on the beam (PDD and beam profile). The linearity of the system’s response to successive pulses was tested and found to be <2% only for irradiation with two or more pulses. Therefore, a single pulse calibration of the system was performed to verify the applicability of the system for single pulse irradiation. The measurement results showed that the differences between the results obtained by the different methods were less than 2% for triode grid voltages below 30 V.

Conclusion: The results confirmed the possibility of using the real-time dosimetry system to measure doses on the sample surface delivered by ultra-high dose rate beams at the AQURE FLASH RT accelerator. The system has been tested and validated over the full range of dose rates emitted by the accelerator to measure a dose in a single pulse. The results of the dosimetric measurements confirmed that the system did not affect the beam parameters.