ESTRO 2025 - Abstract Book

S3562

Physics - Optimisation, algorithms and applications for ion beam treatment planning

ESTRO 2025

4210

Digital Poster Introduce a novel Spot-scanning Proton Arc optimization algorithm for Singe Energy Extraction Synchrotron Accelerator-Based Proton Therapy System Xiaoda Cong 1 , Jiajian Shen 2 , Peilin Liu 1 , Gang Liu 3 , Xuanfeng Ding 1 1 Radiation Oncology, Corewell Health, Royal Oak, USA. 2 Radiation Oncology, Mayo Clinic, Scottsdale, USA. 3 Radiation Oncology, Union Hospital, Wuhan, China Purpose/Objective: SPArc has drawn significant interest from the particle therapy community because of its outstanding target dose conformity, Organs-At-Risk (OARs) sparing, and Linear Energy Transfer (LET) modulation. 1,2 However, all the existing SPArc optimization algorithms are only designed for cyclotron accelerators (PTS -cyclotron ) instead of synchrotron accelerator-based Proton Therapy Systems with the Single Energy Extraction (SEE) technique (PTS -synchroton-SEE ). The PTS -synchroton-SEE delivers a bunch of proton particles through each cycle. The remaining proton particles of that specific energy layer will be discarded if not used, which could result in a significantly prolonged treatment delivery time for the Spot-scanning Proton Arc (SPArc) plan compared to PTS -cyclotron due to the 2 seconds of cycling time. 3 Thus, this study aims to develop the first SPArc optimization algorithm based on the Dynamic Programming (SPArc -DP ), to improve the treatment delivery efficiency for PTS -synchrotron-SEE. Material/Methods: Dynamic Programming, initially designed for combinational optimizations in fields of bioinformatics, finance and scheduling, was introduced to optimize the energy layer and MU distribution based on the features from the PTS synchroton-SEE . It started from a plan generated via the original SPArc algorithm (SPArc -original ) 1 . Based on the maximum charges per extraction, it iteratively merges the adjacent energy layers into the same energy layer while ensuring the plan quality. Thus, it effectively reduces the unnecessary cycling from the PTS -synchroton-SEE by maximizing the utilization rate of each spill . Five representative disease sites are selected for testing purposes, including the base of skull chordoma, bilateral HN, prostate, lung, and liver cancers. The SPArc -original plans are used as benchmarks. Dosimetric quality, including Dose-volume Histogram (DVH), target coverage, and OARs sparing, were evaluated, and the total number of cycles, utilization rate of each spill, and total treatment delivery time were simulated and compared between SPArc -original and SPArc -DP using a dynamic arc system controller 4 . Results: With a similar plan quality (Figure 1), the SPArc -DP plans reduced an average of 118.80 ± 80.67 acceleration cycles and improved the average utilization rate per spill by 28% ± 31%. These improvements effectively saved total treatment delivery time by 239.67s ± 243.90s (relatively 43% ± 15%) compared to SPArc -original plans (Table 1).