Department of Radiology, 38146University of Yamanashi, Yamanashi, Japan.
Technol Cancer Res Treat. 2022 Jan-Dec;21:15330338221119752. doi: 10.1177/15330338221119752.
We aimed to investigate the effects of different multi-leaf collimator (MLC) speed constraints in volumetric modulated radiotherapy (VMAT) on the robustness of treatment plans for central lung cancer patients. Twenty patients with central lung tumor who underwent stereotactic body radiotherapy (SBRT) with the VMAT technique at our hospital were included in this retrospective study. The reference plans were created with 3 different MLC speed constraints (Plan A: 0.1 cm/deg., Plan B: 0.3 cm/deg., and Plan C: 0.5 cm/deg.) with a 50-Gy/8Fr, planning target volume (PTV) D prescription. In each of these plans, setup errors from 1 to 5 mm were intentionally added in the direction of the central organ at 1-mm intervals (300 plans [20 cases × 3 MLC speeds × 5 error plans] were created in total). Each plan was then calculated by the same beam conditions as each reference plan. The actual average MLC speed and dose difference between the reference plan and the error-added plan were then calculated and compared among the 3 MLC speeds. In the reference plans, the actual average MLC speeds were 0.25 ± 0.04, 0.34 ± 0.07, and 0.39 ± 0.12 cm/deg. for Plan A, Plan B, and Plan C, respectively ( < .05). For PTV and OARs, many dose indices tended to improve as the MLC speed increased, while no significant differences were observed among the 3 MLC speed constraints. However, in assessments of robustness, no significant differences in dose difference were observed among the 3 MLC speed constraints for most of the indices. When necessary, increasing the MLC speed constraint with a priority on improving the quality of the dose distribution is an acceptable approach for central lung cancer patients.
我们旨在研究不同多叶准直器（MLC）速度限制在容积调强放疗（VMAT）中对中央肺癌患者治疗计划稳健性的影响。本回顾性研究纳入了 20 例在我院接受立体定向体部放疗（SBRT）VMAT 技术治疗的中央肺肿瘤患者。参考计划采用 3 种不同 MLC 速度限制（计划 A：0.1cm/deg.，计划 B：0.3cm/deg.，计划 C：0.5cm/deg.），50Gy/8Fr，计划靶区（PTV）D 处方。在每个计划中，在中央器官方向以 1mm 间隔故意添加 1 至 5mm 的设置误差（总共创建了 300 个计划[20 例×3 个 MLC 速度×5 个误差计划]）。然后，按照与参考计划相同的射束条件计算每个计划。然后计算并比较了 3 种 MLC 速度之间参考计划和添加误差计划之间的实际平均 MLC 速度和剂量差异。在参考计划中，实际平均 MLC 速度分别为计划 A、计划 B 和计划 C 的 0.25±0.04、0.34±0.07 和 0.39±0.12cm/deg.（ < .05）。对于 PTV 和 OAR，随着 MLC 速度的增加，许多剂量指数往往会改善，而在 3 种 MLC 速度限制之间未观察到显著差异。然而，在稳健性评估中，对于大多数指数，在 3 种 MLC 速度限制之间未观察到剂量差异的显著差异。在必要时，优先提高剂量分布质量增加 MLC 速度限制是中央肺癌患者可接受的方法。
