Department of Radiation Oncology, Kaiser Permanente, Dublin, California, USA.
J Appl Clin Med Phys. 2023 Nov;24(11):e14108. doi: 10.1002/acm2.14108. Epub 2023 Aug 1.
The purpose of this study was to investigate the impact of using flattening filter-free (FFF) beams and the aperture shape controller (ASC) on the complexity of conventional large-field treatment plans.
A total of 24 head and neck (H&N) and 24 prostate with pelvic nodes treatment plans were used in this study. Each plan was reoptimized using the original clinical objectives with both flattened and FFF beams, as well as six different ASC settings. The dosimetric qualities of each plan cohort were evaluated using commonly used dose-volume histogram values, and plan complexities were assessed through metrics including monitor unit (MU)/Dose, change in gantry speed, multileaf collimator (MLC) speed, the edge area ratio metric (EM), and the equivalent square length.
No significant differences in dosimetric qualities were found between plans with flattened and FFF beams. The ASC settings did not have significant effects on dosimetric qualities in the H&N plan cohort, but the "very high" ASC setting resulted in poorer dosimetric results for the prostate plans. Plans with FFF beams had significantly higher MU/Dose compared to plans with flattened beams. The use of flattening filter (FF) had significant effects on the change in gantry speed, with flattened beams producing plans that required higher change in gantry speed. However, the FF did not have significant effects on MLC speed, EM, or equivalent square length. In contrast, ASC settings had significant effects on these three metrics; increasing the ASC level resulted in plans with decreasing MLC speed, lower edge area ratio, and higher equivalent square length.
This study demonstrated that using FFF beams with various ASC settings, except for the "very high" level, can produce plans with reduced complexities without compromising dosimetric qualities in conventional large-field treatment plans.
本研究旨在探讨使用非均整滤过（FFF）射束和孔径形状控制器（ASC）对常规大野治疗计划复杂性的影响。
本研究共使用了 24 例头颈部（H&N）和 24 例盆腔淋巴结前列腺治疗计划。每个计划均使用原始临床目标重新进行优化，同时使用了原始射束和 FFF 射束，以及六种不同的 ASC 设置。通过常用剂量-体积直方图值评估每个计划队列的剂量学质量，并通过监测器单位（MU）/剂量、机架速度变化、多叶准直器（MLC）速度、边缘面积比指标（EM）和等效正方形长度等指标评估计划复杂性。
在具有均匀和 FFF 射束的计划之间，剂量学质量没有显著差异。在 H&N 计划队列中，ASC 设置对剂量学质量没有显著影响，但“非常高”的 ASC 设置导致前列腺计划的剂量学结果较差。与具有均匀射束的计划相比，使用 FFF 射束的计划的 MU/Dose 显著更高。使用均整滤过（FF）对机架速度变化有显著影响，均匀射束产生需要更高的机架速度变化的计划。然而，FF 对 MLC 速度、EM 或等效正方形长度没有显著影响。相比之下，ASC 设置对这三个指标有显著影响；增加 ASC 水平会导致 MLC 速度降低、边缘面积比降低和等效正方形长度增加的计划。
本研究表明，除了“非常高”水平之外，使用各种 ASC 设置的 FFF 射束可以在不影响常规大野治疗计划剂量学质量的情况下产生复杂性降低的计划。
