BACKGROUND AND PURPOSE Patients were treated at our institute for single and multiple lymph node oligometastases on the 1.5T MR-linac since August 2018. The superior soft-tissue contrast and additional software features of the MR-linac compared to CBCT-linacs allow for online adaptive treatment planning. The purpose of this study was to perform a target coverage and dose criteria based evaluation of the clinically delivered online adaptive radiotherapy treatment compared with conventional CBCT-linac treatment. MATERIALS AND METHODS Patient data was used from 14 patients with single lymph node oligometastases and 6 patients with multiple (2-3) metastases. All patients were treated on the 1.5T MR-linac with a prescribed dose of 5 × 7 Gy to 95% of the PTV and a CBCT-linac plan was created for each patient. The difference in target coverage between these plans was compared and plans were evaluated based on dose criteria for each fraction after calculating the CBCT-plan on the daily anatomy. The GTV coverage was evaluated based on the online planning and the post-delivery MRI. RESULTS For both single and multiple lymph node oligometastases the GTV V35Gy had a median value of 100% for both the MR-linac plans and CBCT-plans pre- and post-delivery and did not significantly differ. The percentage of plans that met all dose constraints was improved from 19% to 84% and 20% to 67% for single and multiple lymph node cases, respectively. CONCLUSION Target coverage and dose criteria based evaluation of the first clinical 1.5T MR-linac SBRT treatments of lymph node oligometastases compared with conventional CBCT-linac treatment shows a smaller amount of unplanned violations of high dose criteria. The GTV coverage was comparable. Benefit is primarily gained in patients treated for multiple lymph node oligometastases: geometrical deformations are accounted for, dose can be delivered in one plan and margins can be reduced.

中文翻译：

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与传统 CBCT-linac 治疗相比，淋巴结寡转移的首次临床 1.5T MR-linac SBRT 治疗的靶覆盖率和剂量标准评估

背景和目的 自 2018 年 8 月以来，患者在我们研究所接受 1.5T MR-linac 单淋巴结和多淋巴结寡转移治疗。适应性治疗计划。本研究的目的是对临床提供的在线自适应放疗治疗与传统 CBCT-直线加速器治疗进行比较，进行基于靶覆盖和剂量标准的评估。材料和方法 使用来自 14 名单淋巴结寡转移患者和 6 名多发 (2-3) 转移患者的患者数据。所有患者均接受 1.5T MR-linac 治疗，处方剂量为 5 × 7 Gy 至 PTV 的 95%，并为每位患者制定了 CBCT-linac 计划。比较这些计划之间目标覆盖的差异，并在计算每日解剖结构的 CBCT 计划后，根据每个部分的剂量标准对计划进行评估。基于在线规划和产后 MRI 评估 GTV 覆盖率。结果 对于单个和多个淋巴结寡转移，MR-linac 计划和​​ CBCT 计划在分娩前和分娩后的 GTV V35Gy 的中值为 100%，并且没有显着差异。对于单个和多个淋巴结病例，满足所有剂量限制的计划百分比分别从 19% 提高到 84% 和 20% 到 67%。结论 基于目标覆盖率和剂量标准的第一次临床评估。与传统的 CBCT-linac 治疗相比，5T MR-linac SBRT 对淋巴结寡转移的治疗显示出更少量的计划外违反高剂量标准的情况。GTV 的报道是可比的。受益主要是在接受多淋巴结寡转移治疗的患者中获得的：几何变形被考虑在内，可以在一个计划中提供剂量，并且可以减少边缘。