A novel approach for spot boosting selection and treatment plan optimization to enhance prompt gamma monitoring of proton therapy

Background and Purpose: monitoring can help address these limitations. Prompt-gamma (PG) imaging is a monitoring technique suitable for adaptive particle therapy, though it suffers from low signal at typical fraction doses. A treatment planning strategy was evaluated, that boosts selected spots to enhance monitoring. Material and Methods: A prostate and a head-and-neck plans were generated with a research version of RayStation (RaySearch, Sweden) treatment planning system. A detailed workflow was implemented to select candidate spots to artificially increase the number of protons (boosting) delivered according to specific criteria. Two boosting modalities were applied: (1) assigning a fixed number of protons per boosted spot; (2) maximizing the number of protons, given a lower bound. Reoptimized, boosted plans were compared to the initial one in terms of dose, dose-averaged linear-energy-transfer (LET), LET-weighted dose and robustness. Results: PG signals after boosting confirmed higher number of counts and noise level reduction. Conclusions: Spot boosting is a feasible approach to enhance monitoring with secondary radiation, like PG, without compromising the plan quality. Its integration into clinics could enable an improved delivery quality assurance and a more precise proton therapy.