Search for practical scaling factors of Bragg peak arrangement for line-scanning proton beam therapy in RayStation

To enhance the efficiency of treatment planning and beam delivery in line-scanning proton beam therapy, we conducted a comparative analysis of various strategies for arranging the Bragg peak within the optimization of treatment plans. In RayStation, we had the flexibility to manipulate optimization parameters, specifically energy layer and line spacing, to control the Bragg peak’s location. To assess the impact of these parameters, we created a virtual spherical target and generated treatment plans employing both single and dual beams with diverse arrangement strategies. We then evaluated the target volume coverage using the homogeneity index. Furthermore, we selected 15 line-scanning plans. For each line-scanning plan, we generated nine comparative plans, employing distinct Bragg peak arrangement strategies. These strategies involved variations in energy layer and line spacing settings. We optimized these plans and compared their quality to the default setting. In addition, treatment planning and beam delivery efficiency were estimated. Our analysis indicated that smaller energy layer and line spacing generally resulted in improved homogeneity indices. Notably, reducing line spacing proved to be more efficient than decreasing energy layer spacing, a trend that remained consistent in the line-scanning plans. For line-scanning plans, adjustments in line spacing produced more efficient improvements in the conformity index and D_1cc. Based on our findings, adjusting line spacing is a more effective strategy for optimizing Bragg peak placement in RayStation. This adjustment not only enhances treatment planning but also improves beam delivery efficiency by reducing the time required for energy layer switching.