7005Beaumont Health, Troy, MI, USA.
7005Beaumont Health, Royal Oak, MI, USA.
Technol Cancer Res Treat. 2021 Jan-Dec;20:15330338211038490. doi: 10.1177/15330338211038490.
In this study, we investigate linac volumetric-modulated arc therapy (VMAT) planning strategies for bilateral hip prostheses prostate patients with respect to plan quality and deliverability, while limiting entrance dose to the prostheses. Three VMAT plans were retrospectively created for 20 patients: (1) partial arcs (PA), (2) 2 full arcs optimized with 500 cGy max prostheses dose (MD), and (3) 2 full arcs optimized with max dose-volume histogram (DVH) constraint of 500 cGy to 10% prostheses volume (MDVH). PA techniques contained 6 PA with beam angles that avoid entering each prosthesis. For each patient, other than prostheses constraints, the same Pinnacle VMAT optimization objectives were used. Plans were normalized with PTV D95% = 79.2 Gy prescription dose. Organ-at-risk DVH metrics, monitor units (MUs), conformality, gradient, and homogeneity indices were evaluated for each plan. Mean entrance prosthesis dose was determined in Pinnacle by converting each arc into static beams and utilizing only control points traversing each prosthesis. Plan deliverability was evaluated with SunNuclear ArcCheck measurements (gamma criteria 3%/2 mm) on an Elekta machine. MD and MDVH had similar dosimetric quality, both improved DVH metrics for rectum and bladder compared to PA. Plan complexities among all plans were similar (average MUs: 441-518). Conformality, homogeneity, and gradient indices were significantly improved in MD and MDVH versus PA ( < .001). Gamma pass rates for MD (99.0 ± 1.2%) and MDVH (99.2 ± 0.99%) were comparable. A significant difference over PA was observed (96.8 ± 1.6%, < .001). Field-by-field analysis demonstrated 12/20 PA plans resulted in fields with pass rates <95% versus 1/20 plans for MD and none for MDVH. Cumulative mean entrance doses to each prosthesis were 62.9 ± 17.7 cGy for MD plans and 83.4 ± 27.5 cGy for MDVH plans. MD and MDVH plans had improved dosimetric quality and deliverability over PA plans with minimal entrance doses (∼1% of prescription) to each prosthesis and are an improved alternative for bilateral prostheses prostate patients.
在这项研究中，我们针对双侧髋关节假体前列腺患者的计划质量和可交付性，研究了直线加速器容积调强弧形治疗（VMAT）计划策略，同时限制假体的入口剂量。 回顾性地为 20 名患者创建了 3 种 VMAT 计划：（1）部分弧形（PA），（2）2 个全弧形，优化 500cGy 最大假体剂量（MD），（3）2 个全弧形，优化最大剂量体积直方图（DVH）约束为 500cGy 至 10%假体体积（MDVH）。PA 技术包含 6 个避开每个假体进入的 PA 射束角度。对于每个患者，除了假体约束外，还使用了相同的 Pinnacle VMAT 优化目标。通过将每个弧形转换为静态射束，并仅使用穿过每个假体的控制点，对计划进行归一化。利用 Pinnacle 将 PTV D95% = 79.2Gy 处方剂量。评估了每个计划的危及器官剂量体积直方图（DVH）指标、监测单位（MU）、适形性、梯度和均匀性指数。通过将每个弧形转换为静态射束并仅使用穿过每个假体的控制点，在 Pinnacle 中确定平均入口假体剂量。使用 Elekta 机器上的 SunNuclear ArcCheck 测量（伽马标准 3%/2mm）评估计划的可交付性。MD 和 MDVH 的剂量学质量相似，与 PA 相比，直肠和膀胱的 DVH 指标均得到改善。所有计划的计划复杂性相似（平均 MU：441-518）。MD 和 MDVH 与 PA 相比，适形性、均匀性和梯度指数均显著提高（ < .001）。MD（99.0 ± 1.2%）和 MDVH（99.2 ± 0.99%）的伽马通过率相当。与 PA 相比，观察到显著差异（96.8 ± 1.6%， < .001）。场对场分析表明，与 MD 相比，20 个 PA 计划中有 12 个计划导致通过率<95%，而 MDVH 计划中只有 1 个计划通过率<95%。每个假体的累积平均入口剂量分别为 MD 计划的 62.9 ± 17.7cGy 和 MDVH 计划的 83.4 ± 27.5cGy。MD 和 MDVH 计划在剂量学质量和可交付性方面优于 PA 计划，同时对每个假体的入口剂量（约为处方剂量的 1%）最小化，是双侧假体前列腺患者的一种改进选择。
