Department of Radiation Oncology, University Hospital Zurich, Zurich, Switzerland.
Strahlenther Onkol. 2021 Dec;197(12):1093-1103. doi: 10.1007/s00066-021-01771-8. Epub 2021 Apr 23.
Purpose of this study is to evaluate plan quality on the MRIdian (Viewray Inc., Oakwood Village, OH, USA) system for head and neck cancer (HNC) through comparison of planning approaches of several centers.
A total of 14 planners using the MRIdian planning system participated in this treatment challenge, centrally organized by ViewRay, for one contoured case of oropharyngeal carcinoma with standard constraints for organs at risk (OAR). Homogeneity, conformity, sparing of OARs, and other parameters were evaluated according to The International Commission on Radiation Units and Measurements (ICRU) recommendations anonymously, and then compared between centers. Differences amongst centers were assessed by means of Wilcoxon test. Each plan had to fulfil hard constraints based on dose-volume histogram (DVH) parameters and delivery time. A plan quality metric (PQM) was evaluated. The PQM was defined as the sum of 16 submetrics characterizing different DVH goals.
For most dose parameters the median score of all centers was higher than the threshold that results in an ideal score. Six participants achieved the maximum number of points for the OAR dose parameters, and none had an unacceptable performance on any of the metrics. Each planner was able to achieve all the requirements except for one which exceeded delivery time. The number of segments correlated to improved PQM and inversely correlated to brainstem D and to Planning Target Volume1 (PTV) D. Total planning experience inversely correlated to spinal canal dose.
Magnetic Resonance Image (MRI) linac-based planning for HNC is already feasible with good quality. Generally, an increased number of segments and increasing planning experience are able to provide better results regarding planning quality without significantly prolonging overall treatment time.
本研究旨在通过比较多个中心的计划方法，评估 MRIdian（Viewray Inc.，俄亥俄州奥克伍德村）系统在头颈部癌症（HNC）中的计划质量。
共有 14 名使用 MRIdian 计划系统的规划师参与了这项由 ViewRay 集中组织的治疗挑战，针对一例具有标准危及器官（OAR）限制的口咽癌进行了轮廓勾画。根据国际辐射单位和测量委员会（ICRU）的建议匿名评估均匀性、适形性、OAR 保护和其他参数，然后在中心之间进行比较。通过 Wilcoxon 检验评估中心之间的差异。每个计划都必须满足基于剂量-体积直方图（DVH）参数和治疗时间的硬约束。评估了计划质量指标（PQM）。PQM 定义为 16 个特征不同 DVH 目标的子指标的总和。
对于大多数剂量参数，所有中心的中位数评分均高于导致理想评分的阈值。六名参与者在 OAR 剂量参数方面获得了最高分数，并且在任何指标上都没有表现不佳。每个规划师都能够满足所有要求，除了一名规划师的治疗时间超过了要求。段数与 PQM 呈正相关，与脑干 D 和计划靶区 1（PTV1）D 呈负相关。总规划经验与脊髓剂量呈负相关。
基于磁共振成像（MRI）直线加速器的 HNC 计划已经具有良好的质量。通常，增加段数和增加规划经验能够在不显著延长总治疗时间的情况下，提供更好的计划质量结果。
