Department of Radiation Oncology, Xijing Hospital, Air Force Medical University, Xi'an, China.
Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut, USA.
J Appl Clin Med Phys. 2024 Jul;25(7):e14317. doi: 10.1002/acm2.14317. Epub 2024 Mar 4.
Patient setup errors have been a primary concern impacting the dose delivery accuracy in radiation therapy. A robust treatment plan might mitigate the effects of patient setup errors. In this reported study, we aimed to evaluate the impact of translational and rotational errors on the robustness of linac-based, single-isocenter, coplanar, and non-coplanar volumetric modulated arc therapy treatment plans for multiple brain metastases.
Fifteen patients were retrospectively selected for this study with a combined total of 49 gross tumor volumes (GTVs). Single-isocenter coplanar and non-coplanar plans were generated first with a prescribed dose of 40 Gy in 5 fractions or 42 Gy in 7 fractions to cover 95% of planning target volume (PTV). Next, four setup errors (+1 and +2 mm translation, and +1° and +2° rotation) were applied individually to generate modified plans. Different plan quality evaluation metrics were compared between coplanar and non-coplanar plans. 3D gamma analysis (3%/2 mm) was performed to compare the modified plans (+2 mm and +2° only) and the original plans. Paired t-test was conducted for statistical analysis.
After applying setup errors, variations of all plan evaluation metrics were similar (p > 0.05). The worst case for V100% to GTV was 92.07% ± 6.13% in the case of +2 mm translational error. 3D gamma pass rates were > 90% for both coplanar (+2 mm and +2°) and the +2 mm non-coplanar groups but was 87.40% ± 6.89% for the +2° non-coplanar group.
Translational errors have a greater impact on PTV and GTV dose coverage for both planning methods. Rotational errors have a greater negative impact on gamma pass rates of non-coplanar plans. Plan evaluation metrics after applying setup errors showed that both coplanar and non-coplanar plans were robust and clinically acceptable.
患者摆位误差一直是影响放射治疗剂量准确性的主要问题。一个稳健的治疗计划可能会减轻患者摆位误差的影响。在这项报告的研究中，我们旨在评估平移和旋转误差对基于直线加速器的多脑转移单等中心共面和非共面容积调制弧形治疗计划的稳健性的影响。
本研究回顾性选择了 15 名患者，共有 49 个大体肿瘤体积（GTV）。首先，为每个患者生成单等中心共面和非共面计划，处方剂量为 40 Gy/5 次或 42 Gy/7 次，以覆盖 95%的计划靶体积（PTV）。然后，分别对每个计划应用 4 种摆位误差（+1 和 +2 mm 平移，+1°和 +2°旋转），生成修改后的计划。比较共面和非共面计划之间的不同计划质量评估指标。对修改后的计划（仅+2 mm 和+2°）和原始计划进行 3%/2 mm 的三维伽马分析（3D gamma analysis）比较。采用配对 t 检验进行统计学分析。
在应用摆位误差后，所有计划评估指标的变化相似（p > 0.05）。在 +2 mm 平移误差的情况下，GTV 的 V100%最差为 92.07%±6.13%。对于共面（+2 mm 和+2°）和+2 mm 非共面组，3D 伽马通过率均>90%，但对于+2°非共面组，3D 伽马通过率为 87.40%±6.89%。
平移误差对两种计划方法的 PTV 和 GTV 剂量覆盖有更大的影响。旋转误差对非共面计划的伽马通过率有更大的负面影响。应用摆位误差后的计划评估指标表明，共面和非共面计划均稳健且临床可接受。
