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Experimental verification of the applicability of the AQURE IOERT accelerator for FLASH radiotherapy

Lenartowicz-Gasik Aleksandra, Misiarz Agnieszka, Adrich Przemysław, Wronka Sławomir, Piotrowski Tomasz, Pawałowski Bartosz, Nowaczyk Piotr, Trzuskowski Jan, Rzadkiewicz Jacek

Polish Journal of Medical Physics and Engineering

2025

Vol. 31, Iss. 1

62--72

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.

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

Lenartowicz-Gasik Aleksandra, Misiarz Agnieszka, Markopolski Vasyl, Walo Marta, Gryczka Urszula, Bułka Sylwester, Pawałowski Bartosz, Kruszyna-Mochalska Marta, Rzadkiewicz Jacek

Polish Journal of Medical Physics and Engineering

2024

Vol. 30, Iss. 4

300--304

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.