Proton radiotherapy spot order optimization to maximize the FLASH effect

Cancer is a group of deadly diseases, to which one treatment method is radiotherapy. Recent studies indicate advantages of delivering so-called FLASH treatments using ultra-high dose rates (> 40 Gy/s), with a normal tissue sparing FLASH effect. Delivering a high dose in a short time imposes requirements on both the treatment machine and the treatment plan. To see as much of the FLASH effect as possible, the delivery pattern should be optimized, which is the focus of this thesis. The optimization method was applied to 17 lung plans, and the results show that a local-search-based optimization achieves overall good results, achieving a mean FLASH coverage of 31.7 % outside of the CTV after a mean optimization time of 8.75 s. This is faster than published results using a genetic algorithm