Applications of Accelerators and Detectors to Cancer Treatment

Abstract:

The discovery of the FLASH effect has revealed a high potential for treating cancer more efficiently by sparing healthy tissue. The surge in related medical research activities over the last couple of years has triggered a demand for technology with the capability of generating and measuring ionizing radiation at ultra-high dose-rates (UHDR). A reliable dosimetry system is an integral part of a radiotherapy machine. Because existing active dosimetry methods are unable to handle the dose-rates required for FLASH, UHDR dosimetry has emerged as an important area of research. In this paper we present an active dosimetry method based on a scintillating screen and an integrating current transformer. This method provides a simultaneous measurement of the absolute dose delivery as well as the 2D dose distribution. The measurements have been correlated with corresponding readings from radiochromic films (RCFs), and a procedure for image processing has been established. Moreover, different methods of calibrating the active dosimetry system against RCFs have been introduced and evaluated. Lastly, we present results which demonstrate that an agreement with RCFs of better than 5% can be realistically expected if camera parameters are carefully optimized.

Abstract:

Background: Baltic States remains one of the few regions in the Europe without a dedicated particle therapy center. An initiative since 2021 has been started by CERN Baltic Group on a novel particle therapy center development in the region in partnership with CERN NIMMS collaboration. With a conceptual design idea in early 2022 and stakeholder engagement activities in late 2022 - next step forward was necessary for the initiative for a more in-depth analysis. Methods: A dedicated workshop “Particle therapy - future for the Baltic States? State-of-play, synergies and challenges” was held. The workshop was attended by medical community from the Baltics, as well as CERN technical experts and particle therapy practicing clinicians, with scientific programme split in 5 main areas of investigation. Results: Current cancer epidemiology statistics and RT technological possibilities in the region were analyzed, with first estimates of eligible number of patients calculated. Technological development level of the proposed accelerator complex was discussed, as well the clinical needs and synnergy possibilities with the nuclear medicine field. Conclusions: The current state and calculated first estimates presented here have shown a promising starting point, which prompts even further in-depth work – a feasibility study for development of a novel particle therapy center in the Baltic States.

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