Electron FLASH beams from a modified Elektra Precise LINAC: characterisation and dosimetry

This research explores advanced techniques in radiotherapy to enhance treatment efficacy and reduce side effects. The conventional approach involves fractionated doses of ionising radiation, delivered through techniques like 3D conformal radiotherapy, intensity-modulated radiotherapy, volumetric modulated arc therapy, and stereotactic ablative radiotherapy. FLASH radiotherapy, utilising ultra-high dose rates, has emerged as a promising avenue to improve the therapeutic ratio by swiftly irradiating targets. The primary objective of this study is to investigate the feasibility of adapting a standard linear accelerator (LINAC) for conventional radiotherapy to produce FLASH-level electron beams. The study employs Monte Carlo (MC) simulations to model a LINAC, assessing modifications for FLASH-level beams and characterising resulting beams using diverse detectors, including a novel inorganic scintillator detector. The MC model, validated against measurements, demonstrates robust agreement for both conventional and modified LINAC settings. It proves valuable in validating dosimetry detectors under FLASH irradiation, assessing dose, dose rate, and dose per pulse (DPP) dependencies. The second objective involves characterising dosimetric detectors using a modified LINAC to generate an electron FLASH beam for radiotherapy (eFLASH-RT). By adapting a 12 MeV electron beam, the study establishes radiobiologically relevant FLASH conditions through MC simulations. The results show good agreement between simulated and measured data for reference depths and beam profiles in both conventional and eFLASH setups. The study suggests the potential for online real-time radiation dose evaluation during therapy.

The final part explores the use of novel detectors for real-time dosimetry in ultra-high dose rate applications. The study employs inorganic scintillating detectors (ISD) and plastic scintillation detectors (PSD) with short temporal resolution. These detectors, tested under a 12-MeV electron FLASH beam, exhibit favorable linearity, repeatability, and DPP characteristics. The detectors, integrated into the HYPERSCINT platform, demonstrate a robust response to ultra-high dose rates, offering a versatile dosimetry platform for various research domains.
In conclusion, this research contributes to the advancement of radiotherapy by exploring the feasibility of FLASH-level electron beams, validating dosimetry detectors, and introducing novel detectors for real-time dosimetry in ultra-high dose rate applications. The findings have implications for improving treatment efficacy and understanding the radiobiological impact of ultra-high dose rate irradiation.