PDF(Pubmed)
Abstract：
Purpose. To enhance an in-house graphic-processing-unit accelerated virtual particle (VP)-based Monte Carlo (MC) proton dose engine (VPMC) to model aperture blocks in both dose calculation and optimization for pencil beam scanning proton therapy (PBSPT)-based stereotactic radiosurgery (SRS).Methods and materials. A module to simulate VPs passing through patient-specific aperture blocks was developed and integrated in VPMC based on simulation results of realistic particles (primary protons and their secondaries). To validate the aperture block module, VPMC was first validated by an opensource MC code, MCsquare, in eight water phantom simulations with 3 cm thick brass apertures: four were with aperture openings of 1, 2, 3, and 4 cm without a range shifter, while the other four were with same aperture opening configurations with a range shifter of 45 mm water equivalent thickness. Then, VPMC was benchmarked with MCsquare and RayStation MC for 10 patients with small targets (average volume 8.4 c.c. with range of 0.4-43.3 c.c.). Finally, 3 typical patients were selected for robust optimization with aperture blocks using VPMC.Results. In the water phantoms, 3D gamma passing rate (2%/2 mm/10%) between VPMC and MCsquare was 99.71 ± 0.23%. In the patient geometries, 3D gamma passing rates (3%/2 mm/10%) between VPMC/MCsquare and RayStation MC were 97.79 ± 2.21%/97.78 ± 1.97%, respectively. Meanwhile, the calculation time was drastically decreased from 112.45 ± 114.08 s (MCsquare) to 8.20 ± 6.42 s (VPMC) with the same statistical uncertainties of ~0.5%. The robustly optimized plans met all the dose-volume-constraints (DVCs) for the targets and OARs per our institutional protocols. The mean calculation time for 13 influence matrices in robust optimization by VPMC was 41.6 s and the subsequent on-the-fly \'trial-and-error\' optimization procedure took only 71.4 s on average for the selected three patients.Conclusion. VPMC has been successfully enhanced to model aperture blocks in dose calculation and optimization for the PBSPT-based SRS.
摘要：
目的：增强基于内部图形处理单元（GPU）加速的虚拟粒子（VP）的蒙特卡罗（MC）质子剂量引擎（VPMC），以在剂量计算和优化中对孔径块进行建模基于铅笔束扫描质子治疗（PBSPT）的立体定向放射外科（SRS）。＆＃xD;＆＃xD;方法和材料：根据现实粒子（初级质子及其次级）的模拟结果，开发了一个模拟通过患者特定孔径块的VPs的模块，并将其集成在VPMC中。要验证孔径光阑模块，VPMC首先通过开源MC代码进行验证，MCsquare,在8个3厘米厚黄铜孔的水模模拟中：4个具有1、2、3和4厘米的孔开口，没有范围移位器，而其他四个具有相同的孔径开口配置，具有45mm水等效厚度的范围移位器。然后，VPMC以MCsquare和RayStationMC为基准，针对10例小目标患者（平均体积8.4cc，范围为0.4-43.3cc）。最后,选择3名典型患者使用VPMC对孔径块进行稳健优化。
结果：在水中幻影中，VPMC和MCsquare之间的3D伽马通过率（2％/2mm/10％）为99.71±0.23％。在患者的几何形状中，VPMC/MCsquare和RayStationMC之间的3D伽马通过率（3％/2mm/10％）为97.79±2.21％/97.78±1.97％，分别。同时,计算时间从112.45±114.08秒（MCsquare）急剧减少到8.20±6.42秒（VPMC），相同的统计不确定性为〜0.5％。根据我们的机构协议，经过优化的计划满足了目标和OAR的所有剂量-体积约束（DVC）。在VPMC的稳健优化中，13个影响矩阵的平均计算时间为41.6秒，随后的“试错”优化程序平均仅花费了71.4秒。＆＃xD;＆＃xD;结论：VPMC已成功增强，可在基于PBSPT的SRS的剂量计算和优化中对孔径块进行建模。
