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Abstract:

Purpose: This study provides a comprehensive overview of the progress in hadron therapy within Europe, particularly highlighting the critical roles of the Proton Ion Medical Machine Study (PIMMS) and the European Network for Light Ion Hadron Therapy (ENLIGHT). Methods: Our approach includes a retrospective analysis of the advances in hadron therapy facilities, facilitated by a synthesis of interdisciplinary collaboration data gathered from ENLIGHT's annual meetings since 2002, and an assessment of European-funded projects and networks' contributions to the field. Results: The results showcase significant advancements in cancer treatment due to collective efforts in hadron therapy, underscored by ENLIGHT’s pivotal role in fostering interdisciplinary cooperation and the harmonization of treatment protocols across Europe. Conclusion: The evolution of hadron therapy, from its inception to its current impact on patient care, demonstrates the successful realization of complex medical technologies through sustained collaboration and standardized practices across European institutions and projects.

Abstract:

Very High Energy Electrons (VHEE) are a promising radiotherapy modality due to their increased penetration, reduced sensitivity to inhomogeneities, and delivery via scanning or focusing. VHEE beams at ultrahigh dose rates (UHDR) could be beneficial for treating deep-seated tumours using the FLASH effect, which selectively spares healthy tissues while maintaining effective tumour control. One of the main challenges in making VHEE FLASH treatment clinically viable is real-time dosimetry and beam monitoring, as ionisation chambers exhibit non-linear responses at UHDR due to recombination effects. This research addresses this challenge through the characterisation of VHEE interactions using Monte Carlo (MC) simulations, film dosimetry at the CLEAR Facility, and by developing a novel fibre array beam monitor. Using TOPAS MC simulations, the interactions of VHEE beams were characterised. The dose distributions and resulting secondary particles generated from these interactions were evaluated to determine feasible in vivo dose verification methods for VHEE UHDR beams. A radiochromic film dosimetry protocol was developed for VHEE FLASH experiments at the CLEAR Facility to ensure accurate dose measurements. Various Gaussian beam size determination methods were compared. Charge measurements using an integrated current transformer were correlated with dose-area-product measurements on radiochromic films for both UHDR and conventional irradiations. Radiochromic film measurements were also compared to those made with other passive dosimeters to ensure accuracy and reliability. A novel optical fibre beam monitor was developed for real-time beam profile and dose monitoring at UHDR with VHEE beams. Consisting of silica fibres and a CMOS camera, the monitor was tested and characterised at the CLEAR Facility. A linear response with dose rate was demonstrated alongside accurate beam profile measurements for Gaussian and uniform beams. This shows real potential as a solution to address the critical need for accurate beam monitoring with VHEE FLASH radiotherapy

Abstract:

Given the present availability of high-gradient accelerator technology for compact and cost-effective electron linacs in the 100-200 MeV energy range, the interest for Very High Energy Electron (VHEE) radiotherapy (RT) for cancer treatment recently reached an all-time high. Particular significance is assumed by the Ultra-High Dose Rate (UHDR) regime where the so-called FLASH biological effect takes place, in which cancer cells are damaged while healthy tissue is largely spared. VHEE beams from linacs are especially well adapted for FLASH RT, given their penetration depth and the high beam current needed to treat large deep-seated tumours. In recent years, several multidisciplinary user groups carried out a number of studies on VHEE and FLASH RT issues using the CERN Linear Accelerator for Research (CLEAR) user facility, in close collaboration with the local operation team. In this paper, we give an overview of such activities and describe the main results of chemical and biological tests aimed at clarifying the damage mechanisms at the root of the FLASH effect and the relevant beam parameters needed to achieve it. We also describe the dedicated systems and methods developed and used in CLEAR for these activities, focusing on recent advances in the crucial aspects of uniform beam delivery and high dose rate real-time dosimetry.