Recently implemented photon optimizer (PO) MLC optimization algorithm is mandatory for RapidPlan modeling in Eclipse. This report quantifies and compares the dosimetry and treatment delivery parameters of PO vs its predecessor progressive resolution optimizer (PRO) algorithm for a single-dose of volumetric modulated arc therapy (VMAT) lung stereotactic body radiation therapy (SBRT). Clinical SBRT treatment plans for 12 early-stage non–small-cell lung cancer patients receiving 30 Gy in 1 fraction using PRO-VMAT were re-optimized using the PO-VMAT MLC algorithm with identical planning parameters and objectives. Average planning target volume derived from the 4D CT scans was 13.6 ± 12.0 cc (range: 4.3 to 41.1 cc) Patients were treated with 6 MV flattening filter free beam using Acuros-based calculations and 2.5 mm calculation grid-size (CGS). Both treatment plans were normalized to receive same target coverage and identical CGS to isolate effects of MLC positioning optimizers. Original PRO and re-optimized PO plans were compared via RTOG–0915 protocol compliance criteria for target conformity, gradient indices, dose to organs at risks and delivery efficiency. Additionally, PO-VMAT plans with a 1.25 mm CGS were evaluated. Both plans met RTOG protocol requirements. Conformity indices showed no statistical difference between PO 2.5 mm CGS and PRO 2.5 mm CGS plans. Gradient index (p = 0.03), maximum dose to 2 cm away from planning target volume in any direction (D_2cm) (p < 0.05), and gradient distance (p < 0.05) presented statistically significant differences for both plans with 2.5 mm CGS. Some organs at risks showed statistically significant differences for both plans calculated with 2.5 mm CGS; however, no clinically significant dose differences were observed between the plans. Beam modulation factor was statistically significant for both PO 1.25 mm CGS (p = 0.001) and PO 2.5 mm CGS (p < 0.001) compared to clinical PRO 2.5 mm CGS plans. PO-VMAT plans provided decreased beam-on time by an average of 0.2 ± 0.1 minutes (up to 1.0 minutes) with PO 2.5 mm and 1.2 ± 0.39 minutes (maximum up to 3.22 minutes) with PO 1.25 mm plans compared to PRO 2.5 mm plans. PO-VMAT single-dose of VMAT lung SBRT plans showed slightly increased intermediate-dose spillage but boasted overall similar plan quality with less beam modulation and hence shorter beam-on time. However, PO 1.25 mm CGS had less intermediate-dose spillage and analogous plan quality compared to clinical PRO-VMAT plans with no additional cost of plan optimization. Further investigation into peripheral targets with PO-MLC algorithm is warranted. This study indicates that PO 1.25 mm CGS plans can be used for RapidPlan modeling for a single dose of lung SBRT patients. PO-MLC 1.25 mm algorithm is recommended for future clinical single-dose lung SBRT plan optimization.

最近实现的光子优化器 (PO) MLC 优化算法对于 Eclipse 中的 RapidPlan 建模是必需的。该报告量化并比较了 PO与其前身渐进分辨率优化器 (PRO) 算法用于单剂量容积调制弧光疗法 (VMAT) 肺立体定向放射疗法 (SBRT)。使用具有相同计划参数和目标的 PO-VMAT MLC 算法对 12 名使用 PRO-VMAT 分 1 次接受 30 Gy 的早期非小细胞肺癌患者的临床 SBRT 治疗计划进行了重新优化。从 4D CT 扫描得出的平均规划目标体积为 13.6 ± 12.0 cc（范围：4.3 至 41.1 cc） 使用基于 Acuros 的计算和 2.5 毫米计算网格大小 (CGS) 的 6 MV 平整无滤波器光束对患者进行治疗。两种治疗计划都经过标准化以接收相同的目标覆盖范围和相同的 CGS，以隔离 MLC 定位优化器的影响。原始 PRO 和重新优化的 PO 计划通过 RTOG-0915 协议合规性标准进行了比较，包括目标一致性、梯度指数、风险器官的剂量和递送效率。此外，还评估了具有 1.25 毫米 CGS 的 PO-VMAT 计划。这两个计划都符合 RTOG 协议要求。符合性指数显示 PO 2.5 mm CGS 和 PRO 2.5 mm CGS 计划之间没有统计学差异。梯度指数（p  = 0.03)、在任何方向 (D _2cm )距计划目标体积 2 cm 的最大剂量( p < 0.05) 和梯度距离 ( p < 0.05) 显示了两种具有 2.5 mm CGS 的计划的统计学显着差异。对于使用 2.5 mm CGS 计算的两种计划，一些处于危险中的器官显示出统计学上的显着差异；然而，在计划之间没有观察到临床上显着的剂量差异。对于 PO 1.25 mm CGS ( p  = 0.001) 和 PO 2.5 mm CGS ( p< 0.001) 与临床 PRO 2.5 mm CGS 计划相比。与 PRO 2.5 mm 相比，PO-VMAT 计划提供的光束开启时间平均减少 0.2 ± 0.1 分钟（最多 1.0 分钟），PO 2.5 毫米和 1.2 ± 0.39 分钟（最多 3.22 分钟）PO 1.25 毫米计划计划。PO-VMAT 单剂量 VMAT 肺 SBRT 计划显示中等剂量溢出略有增加，但总体计划质量相似，光束调制较少，因此光束接通时间较短。然而，与临床 PRO-VMAT 计划相比，PO 1.25 mm CGS 具有较少的中间剂量溢出和类似的计划质量，且没有额外的计划优化成本。有必要使用 PO-MLC 算法进一步研究外围目标。该研究表明，PO 1.25 mm CGS 计划可用于单剂量肺 SBRT 患者的 RapidPlan 建模。PO-MLC 1.