Abstract：
BACKGROUND: Robust optimization has been suggested as an approach to reduce the irradiated volume in lung Stereotactic Body Radiation Therapy (SBRT). We performed a retrospective planning study to investigate the potential benefits over Planning Target Volume (PTV)-based planning.
METHODS: Thirty-nine patients had additional plans using robust optimization with 5-mm isocenter shifts of the Gross Tumor Volume (GTV) created in addition to the PTV-based plan used for treatment. The optimization included the mid-position phase and the extreme breathing phases of the 4D-CT planning scan. The plans were compared for tumor coverage, isodose volumes, and doses to Organs At Risk (OAR). Additionally, we evaluated both plans with respect to observed tumor motion using the peak tumor motion seen on the planning scan and cone-beam CTs.
RESULTS: Statistically significant reductions in irradiated isodose volumes and doses to OAR were achieved with robust optimization, while preserving tumor dose. The reductions were largest for the low-dose volumes and reductions up to 188 ccm was observed. The robust evaluation based on observed peak tumor motion showed comparable target doses between the two planning methods. Accumulated mean GTV-dose was increased by a median of 4.46 Gy and a non-significant increase of 100 Monitor Units (MU) was seen in the robust optimized plans.
CONCLUSIONS: The robust plans required more time to prepare, and while it might not be a feasible planning strategy for all lung SBRT patients, we suggest it might be useful for selected patients.
METHODS: Thirty-nine patients had additional plans using robust optimization with 5-mm isocenter shifts of the Gross Tumor Volume (GTV) created in addition to the PTV-based plan used for treatment. The optimization included the mid-position phase and the extreme breathing phases of the 4D-CT planning scan. The plans were compared for tumor coverage, isodose volumes, and doses to Organs At Risk (OAR). Additionally, we evaluated both plans with respect to observed tumor motion using the peak tumor motion seen on the planning scan and cone-beam CTs.
RESULTS: Statistically significant reductions in irradiated isodose volumes and doses to OAR were achieved with robust optimization, while preserving tumor dose. The reductions were largest for the low-dose volumes and reductions up to 188 ccm was observed. The robust evaluation based on observed peak tumor motion showed comparable target doses between the two planning methods. Accumulated mean GTV-dose was increased by a median of 4.46 Gy and a non-significant increase of 100 Monitor Units (MU) was seen in the robust optimized plans.
CONCLUSIONS: The robust plans required more time to prepare, and while it might not be a feasible planning strategy for all lung SBRT patients, we suggest it might be useful for selected patients.
摘要：
背景：已建议将稳健优化作为减少肺立体定向身体放射治疗（SBRT）中的辐照体积的方法。我们进行了一项回顾性计划研究，以调查基于计划目标体积（PTV）的计划的潜在收益。
方法：39名患者除了用于治疗的基于PTV的计划外，还使用了5-mm等中心转移的大体肿瘤体积（GTV）的稳健优化进行了其他计划。优化包括4D-CT计划扫描的中间位置阶段和极端呼吸阶段。比较了肿瘤覆盖率的计划，等剂量体积，以及对处于危险中的器官(OAR)的剂量。此外,我们使用在计划扫描和锥形束CT上看到的峰值肿瘤运动评估了两个计划关于观察到的肿瘤运动。
结果：通过稳健优化实现了对OAR的辐照等剂量和剂量的统计学显着减少，同时保留肿瘤剂量。低剂量体积的减少最大，减少量高达188ccm。基于观察到的峰值肿瘤运动的稳健评估表明，两种计划方法之间的目标剂量相当。累积的平均GTV剂量增加了4.46Gy的中值,并且在稳健的优化计划中看到了100个监测单位(MU)的非显著增加。
结论：稳健的计划需要更多的时间来准备，虽然这对所有的肺部SBRT患者来说可能不是一个可行的计划策略，我们建议它可能对选定的患者有用。
方法：39名患者除了用于治疗的基于PTV的计划外，还使用了5-mm等中心转移的大体肿瘤体积（GTV）的稳健优化进行了其他计划。优化包括4D-CT计划扫描的中间位置阶段和极端呼吸阶段。比较了肿瘤覆盖率的计划，等剂量体积，以及对处于危险中的器官(OAR)的剂量。此外,我们使用在计划扫描和锥形束CT上看到的峰值肿瘤运动评估了两个计划关于观察到的肿瘤运动。
结果：通过稳健优化实现了对OAR的辐照等剂量和剂量的统计学显着减少，同时保留肿瘤剂量。低剂量体积的减少最大，减少量高达188ccm。基于观察到的峰值肿瘤运动的稳健评估表明，两种计划方法之间的目标剂量相当。累积的平均GTV剂量增加了4.46Gy的中值,并且在稳健的优化计划中看到了100个监测单位(MU)的非显著增加。
结论：稳健的计划需要更多的时间来准备，虽然这对所有的肺部SBRT患者来说可能不是一个可行的计划策略，我们建议它可能对选定的患者有用。
