Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada.
Department of Medical Physics, Nova Scotia Health Authority, Halifax, Nova Scotia, Canada.
J Appl Clin Med Phys. 2022 Nov;23(11):e13765. doi: 10.1002/acm2.13765. Epub 2022 Sep 2.
Class solution template trajectories are used clinically for efficiency, safety, and reproducibility. The aim was to develop class solutions for single cranial metastases radiotherapy/radiosurgery based on intracranial target positioning and compare to patient-specific trajectories in the context of 4π optimization. Template trajectories were constructed based on the open-source Montreal Neurological Institute (MNI) average brain. The MNI brain was populated with evenly spaced spherical target volumes (2 cm diameter, N = 243) and organs-at-risk (OARs) were identified. Template trajectories were generated for six anatomical regions (frontal, medial, and posterior, each with laterality dependence) based on previously published 4π optimization methods. Volumetric modulated arc therapy (VMAT) treatment plans generated using anatomically informed template 4π trajectories and patientspecific 4π trajectories were compared against VMAT plans from a standard four-arc template. Four-arc optimization techniques were compared to the standard VMAT template by placing three spherical targets in each of six anatomical regions of a test patient. This yielded 54 plans to compare various plan quality metrics. Increasing plan technique complexity, the total number of OAR maximum dose reductions compared to the standard arc template for the 6 anatomical classes was 4+/-2 (OFIXEDc) and 7+/-2 (OFIXEDi). In 65.6% of all cases, optimized fixed-couch positions outperformed the standard-arc template. Of the three comparisons, the most complex (OFIXEDi) showed the greatest statistical significance compared to the least complex (VMATi) across 12 plan quality metrics of maximum dose to each OAR, V12Gy, total plan Monitor Units, conformity index, and gradient index (p < 0.00417). In approximately 70% of all cases, 4π optimization methods outperformed the standard-arc template in terms of maximum dose reduction to OAR, by exclusively changing the arc geometry. We conclude that a tradeoff exists between complexity of a class solution methodology compared to patient-specific methods for arc selection, in the context of plan quality improvement.
类解决方案模板轨迹在临床上用于提高效率、安全性和可重复性。本研究旨在基于颅内靶定位开发适用于单一颅转移放疗/放射外科的类解决方案，并在 4π 优化的背景下与患者特异性轨迹进行比较。模板轨迹基于开源的蒙特利尔神经学研究所（MNI）平均脑进行构建。在 MNI 脑中均匀分布有球形靶区（直径 2cm，N=243），并确定了危及器官（OARs）。基于之前发表的 4π 优化方法，为六个解剖区域（额、内侧和后，每个区域均具有侧依赖性）生成了模板轨迹。使用解剖学上知情的模板 4π 轨迹和患者特异性 4π 轨迹生成容积调强弧形治疗（VMAT）治疗计划，并与标准四弧模板的 VMAT 计划进行比较。通过在测试患者的六个解剖区域中的每个区域中放置三个球形靶区，将四弧优化技术与标准 VMAT 模板进行比较，从而生成了 54 个计划来比较各种计划质量指标。与标准 VMAT 模板相比，随着计划技术复杂性的增加，对于 6 个解剖学类别，总共有 4+/-2（OFIXEDc）和 7+/-2（OFIXEDi）个 OAR 最大剂量减少。在所有情况下的 65.6%中，优化的固定床位置在 12 个 OAR 最大剂量、V12Gy、总计划监控单位、适形指数和梯度指数等所有计划质量指标方面均优于标准弧模板。在三个比较中，与最复杂的（OFIXEDi）相比，最复杂的（VMATi）与最复杂的（VMATi）相比具有最大的统计学意义（p <0.00417）。在大约 70%的所有情况下，4π 优化方法通过仅改变弧几何形状，在 OAR 最大剂量减少方面优于标准弧模板。我们得出结论，在计划质量改善的背景下，类解决方案方法的复杂性与患者特异性的弧选择方法之间存在权衡。
