Department of Radiation Oncology, University of Health Sciences, Gulhane Medical Faculty, Ankara, Turkey.
J Appl Clin Med Phys. 2024 Oct;25(10):e14488. doi: 10.1002/acm2.14488. Epub 2024 Sep 3.
The aim of this study is to determine the effect of forcing and filling the electron density (ED) to 1.0 of the planning target volume (PTV) overdose distribution in lung SBRT treatment leading to shortening patient treatment time and increasing patient comfort by reducing MU/fraction due to ED manipulation effect.
In this study, 36 lung SBRT plans of 12 suitable patients who prescribed a total dose of 50 Gy in five fractions were generated with Monaco v.5.10 TPS using the Monte Carlo (MC) algorithm and volumetric modulated arc therapy (VMAT) technique by PTV ED values forcing as well as filling to 1.0 and comparatively assessed. The first group of plans was created by using the patient's original ED, second and third groups of plans were reoptimized by forcing and filling the ED of PTV to 1.0, respectively, therefore acquiring a new dose distribution which lead to comparatively assessment the effects of changes in ED on PTV and OAR doses.
Assessment of treatment plans revealed that mean MU/fx numbers were decreased by 76% and 75.25% between Groups 1 and 2, Groups 1 and 3, respectively. The number of segments was also reduced in Group 1 by up to 15% compared with Groups 2 and 3. Maximum HI and CI differences for PTV between Groups 1 and 2 were less than 1% and Groups 1 and 3 were 1.5% which indicates all 3 group plans were comparable in terms of dose distribution within PTV.
Forcing and filling the ED of PTV to 1.0 strategy has provided reduced a number of segments and MU/fx without a significant change in PTV mean and maximum doses, thereby decreasing treatment time and patient discomfort during treatment. This process should be considered in line of a potential number of patients as well as prescribed dose and MU/fx numbers.
本研究旨在确定在肺部 SBRT 治疗中，通过迫使和填充计划靶区（PTV）的电子密度（ED）至 1.0，从而缩短患者治疗时间并提高患者舒适度的效果，因为 ED 操作会导致 MU/分数减少。
在这项研究中，为 12 名合适的患者生成了 36 个肺部 SBRT 计划，这些患者的处方剂量为 50 Gy，共 5 个分数。使用 Monaco v.5.10 TPS 中的蒙特卡罗（MC）算法和容积调制弧形治疗（VMAT）技术生成计划，通过迫使和填充 PTV 的 ED 至 1.0，分别对这些计划进行评估。第一组计划是使用患者的原始 ED 创建的，第二组和第三组计划是通过迫使和填充 PTV 的 ED 至 1.0 进行重新优化的，从而获得新的剂量分布，通过比较评估 ED 变化对 PTV 和 OAR 剂量的影响。
治疗计划的评估表明，与组 1 相比，组 2 和组 3 的 MU/fx 数量分别减少了 76%和 75.25%。与组 2 和组 3 相比，组 1 的节段数量也减少了高达 15%。PTV 之间的最大 HI 和 CI 差异在组 1 和组 2 之间小于 1%，在组 1 和组 3 之间为 1.5%，这表明所有 3 组计划在 PTV 内的剂量分布方面是可比的。
迫使和填充 PTV 的 ED 至 1.0 的策略减少了段数和 MU/fx，同时不会显著改变 PTV 的平均和最大剂量，从而减少了治疗时间和患者在治疗过程中的不适。在考虑治疗时间和患者舒适度的情况下，应考虑这种策略。
