Future Developments in Charged Particle Therapy: Improving Beam Delivery for Efficiency and Efficacy

Abstract

The physical and clinical benefits of charged particle therapy (CPT) are well recognised and recent developments have led to the rapid emergence of facilities, resulting in wider adoption worldwide. Nonetheless, the availability of CPT and complete exploitation of dosimetric advantages are still limited by high facility costs and technological challenges. There are extensive ongoing efforts to improve upon these, which will lead to greater accessibility, superior delivery, and therefore better treatment outcomes. The issue of cost however still remains a primary hurdle as the utility of CPT is largely driven by the affordability, complexity and performance of current technology. Several of these aspects can be addressed by developments to the beam delivery system (BDS) which determine the overall shaping and timing capabilities to provide high quality treatments. Modern delivery techniques are necessary but are limited by extended treatment times. The energy layer switching time (ELST) is a limiting constraint of the BDS and a determinant of the beam delivery time (BDT), along with the accelerator and other factors. This review evaluates the delivery process in detail, presenting the limitations and developments for the BDS and related accelerator technology, toward decreasing the BDT. As extended BDT impacts motion and has dosimetric implications for treatment, we discuss avenues to minimise the ELST and overview the clinical benefits and feasibility of a large energy acceptance BDS. These developments support the possibility of delivering advanced methodologies such as volumetric rescanning, FLASH and arc therapy and can further reduce costs given a faster delivery for a greater range of treatment indications. Further work to realise multi-ion, image guided and adaptive therapies is also discussed. In this review we examine how increased treatment efficiency and efficacy could be achieved with an improved BDS and how this could lead to faster and higher quality treatments for the future of CPT.