Muthu Sivakumar, Mudhana Gopinath
Department of Physics, School of Advanced Sciences, Vellore Institute of Technology (VIT), Chennai Campus, Vandalur - Kelambakkam Road, Chennai, Tamil Nadu, 600 127, India.
Department of Radiation Oncology, Sri Shankara Cancer Hospital & Research Centre, Bangalore, 560 004, India.
Jpn J Radiol. 2025 Mar;43(3):520-529. doi: 10.1007/s11604-024-01686-1. Epub 2024 Nov 6.
To optimize NTO parameters in non-coplanar RapidArc (RA) stereotactic radiosurgery (SRS) for multiple brain metastases and compare them with HyperArc (HA) plans.
Thirty patients with multiple brain metastases, receiving 21 Gy prescriptions, were retrospectively enrolled, with lesions ranging from two to eight and volumes between 0.27 and 10.56 cm. Non-coplanar RapidArc plans utilized manual NTO (RA-mNTO) with varying dose fall-off values (0.1 mm, 0.5 mm, 1.0 mm, 2.0 mm, 3.0 mm) and end doses (50%, 25% & 10%). Additionally, two HyperArc plans were generated: HA-ALDO used Automatic Lower Dose Objectives with SRS NTO, while HA-mNTO used the same beam geometry with manual NTO parameters optimized from RA-mNTO plans. TrueBeam with High-Definition Multi-leaf Collimators (HDMLC), 6 MV Flattening Filter Free (FFF) Beam at a maximum dose rate of 1400 MU/min, and Eclipse version 16.1 TPS were used. Plans were assessed for Paddick Conformity Index (CI), Gradient Index (GI), Homogeneity Index (HI), normal brain doses (V, V, and V), Monitor Units (MUs), and delivery accuracy using aS1200 Digital Megavolt Imager (DMI) with 2%/2 mm gamma criteria. Statistical analysis utilized integrated scoring and the Wilcoxon signed-rank test.
RA-mNTO plans with 0.5 mm⁻ dose fall-off and 10% end-dose showed superior dosimetric outcomes: CI (0.85 ± 0.08), GI (3.63 ± 0.87), and HI (0.36 ± 0.06) compared to HA-ALDO (CI 0.84 ± 0.09, GI: 3.97 ± 0.85, HI: 0.39 ± 0.07) and HA-mNTO (CI 0.83 ± 0.08, GI: 3.60 ± 0.93, HI: 0.40 ± 0.06). MUs were comparable: RA-mNTO (9679 ± 1882), HA-ALDO (9509 ± 1315), and higher for HA-mNTO (10,457 ± 1980). RA-mNTO plans exhibited significantly lower normal brain doses (V: 1.78 ± 1.23, V: 3.54 ± 2.37, V: 6.21 ± 4.09) compared to HA-ALDO (V: 2.02 ± 1.34, V: 4.09 ± 2.66, V: 7.15 ± 4.56) and HA-mNTO (V: 1.85 ± 1.20, V: 3.68 ± 2.33, V: 6.36 ± 3.97). All techniques achieved > 98% gamma pass rate.
Non-coplanar RA plans with optimized mNTO settings outperformed HyperArc plans in all studied dosimetric parameters for SRS treatment of multiple brain metastases.
优化非共面 RapidArc（RA）立体定向放射外科（SRS）治疗多发脑转移瘤的 NTO 参数，并将其与 HyperArc（HA）计划进行比较。
回顾性纳入 30 例接受 21 Gy 处方剂量的多发脑转移瘤患者，病灶数量为 2 至 8 个，体积在 0.27 至 10.56 cm 之间。非共面 RapidArc 计划采用手动 NTO（RA-mNTO），具有不同的剂量下降值（0.1 mm、0.5 mm、1.0 mm）和 50%、25%及 10%的末端剂量。此外，生成了两个 HyperArc 计划：HA-ALDO 使用带有 SRS NTO 的自动降低剂量目标，而 HA-mNTO 使用与 RA-mNTO 计划优化后的手动 NTO 参数相同的射束几何形状。使用配备高清多叶准直器（HDMLC）的 TrueBeam、最大剂量率为 1400 MU/min 的 6 MV 无 flattening 滤波器（FFF）射束以及 Eclipse 版本 16.1 治疗计划系统（TPS）。使用 aS1200 数字兆伏成像仪（DMI），根据 2%/2 mm 伽马标准评估计划的 Paddick 适形指数（CI）、梯度指数（GI）均匀性指数（HI）、正常脑剂量（V 、V 、V ）、监测单位（MUs）和照射精度。统计分析采用综合评分和 Wilcoxon 符号秩检验。
与 HA-ALDO（CI 0.84±0.09，GI：3.97±0.85，HI：0.39±0.07）和 HA-mNTO（CI 0.83±0.08，GI：3.60±0.93，HI：0.40±0.06）相比，具有 0.5 mm⁻剂量下降和 10%末端剂量的 RA-mNTO 计划显示出更好的剂量学结果：CI（0.85±0.08）、GI（3.63±0.87）和 HI（0.36±0.06）。MUs 相当：RA-mNTO（9679±1882）、HA-ALDO（9509±1315），而 HA-mNTO 更高（10457±1980）。与 HA-ALDO（V ：2.02±1.34，V ：4.09±2.66，V ：7.15±4.56）和 HA-mNTO（V ：1.85±1.20，V ：3.68±2.33，V ：6.36±3.97）相比，RA-mNTO 计划的正常脑剂量显著更低（V ：1.78±1.23，V ：3.54±2.37，V ：6.21±4.09）。所有技术的伽马通过率均>98%。
在 SRS 治疗多发脑转移瘤的所有研究剂量学参数中，具有优化 mNTO 设置的非共面 RA 计划优于 HyperArc 计划。
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