Spot-scanning proton and heavy ion arc (SHArc) is an emerging topic in the field of ion beam therapy. Other than the conventional ion beam therapy approach, which uses a small number of intensity modulated beams to treat the tumour, SHArc leverages the increased flexibility that comes with irradiation from a large number of beam directions. This can produce a more conformal treatment for certain indications, such as oropharyngeal cancer, and may enable better targeting of radio-resistant tumour regions by focusing the region of high linear energy transfer in hypoxic tumour regions. While gantry-based arc delivery has been developed for protons, for heavy ions, gantries are rare, because of their large size and enormous cost. Upright patient positioning will bring SHArc treatment planning concepts to clinical feasibility. There are, however, multiple challenges to be solved when rotating the patient in front of a fixed beam for SHArc delivery.  

1. New planning algorithms that take into account and optimize on the parameters set by the upright positioning device are needed 
2. The treatment delivery sequence has to be optimized to permit the most efficient delivery, that fits in the clinical workflow at ion beam therapy centres 
3. The upright positioning system needs to be interfaced with the beam delivery system to ensure accurate and safe SHArc irradiation 

The project will tackle these challenges, utilizing state-of-the-art infrastructure available at the GSI. The TRiP98 in-house treatment platform includes a dedicated infrastructure for SHArc plan optimization, including strategies for efficient beam delivery via spot and energy layer reduction techniques. This platform will be further advanced within the DC 5 project to tailor it to the parameter space of upright treatments. Further, a small-scale demonstrator system, already connected to the dose delivery system at GSI’s Cave M, will enable to test the developed ideas in practice. Secondments are planned with Raysearch laboratories in Stockholm, Sweden, to investigate advanced SHArc planning concepts, as well as with the Czech Technical University in Prague for QA of SHArc therapy and the Jagellonian University for investigating PET as a possible SHArc verification technique. Overall, the project offers a fruitful research environment for research in SHArc therapy, enhanced by further collaborations within the SHArc community.