Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, USA.
Mary Bird Perkins Cancer Center, Baton Rouge, LA, USA.
J Appl Clin Med Phys. 2020 Nov;21(11):58-69. doi: 10.1002/acm2.13028. Epub 2020 Oct 26.
Interplay effects in highly modulated stereotactic body radiation therapy lung cases treated with volumetric modulated arc therapy.
To evaluate the influence of tumor motion on dose delivery in highly modulated stereotactic body radiotherapy (SBRT) of lung cancer using volumetric modulated arc therapy (VMAT).
4D-CT imaging data of the quasar respiratory phantom were acquired, using a GE Lightspeed 16-slice CT scanner, while the phantom reproduced patient specific respiratory traces. Flattening filter-free (FFF) dual-arc VMAT treatment plans were created on the acquired images in Pinnacle treatment planning system. Each plan was generated with varying levels of complexity characterized by the modulation complexity score. Static and dynamic measurements were delivered to GafChromic EBT3 film inside the respiratory phantom using an Elekta Versa HD linear accelerator. The treatment prescription was 10 Gy per fraction for 5 fractions. Comparisons of the planned and delivered dose distribution were performed using Radiological Imaging Technology (RIT) software.
For the motion amplitudes and periods studied, the interplay effect is insignificant to the GTV coverage. The mean dose deviations between the planned and delivered dose distribution never went below -2.00% and a minimum dose difference of -5.05% was observed for a single fraction. However for amplitude of 2 cm, the dose error could be as large as 20.00% near the edges of the PTV at increased levels of complexity. Additionally, the modulation complexity score showed an ability to provide information related to dose delivery. A correlation value (R) of 0.65 was observed between the complexity score and the gamma passing rate for GTV coverage.
As expected, respiratory motion effects are most evident for large amplitude respirations, complex fields, and small field margins. However, under all tested conditions target coverage was maintained.
在使用容积旋转调强弧形治疗（VMAT）治疗肺癌的高度调制立体定向体放射治疗（SBRT）中，研究肿瘤运动对剂量分布的影响。
使用容积旋转调强弧形治疗（VMAT）评估在肺癌的高度调制立体定向体放射治疗（SBRT）中肿瘤运动对剂量分布的影响。
使用通用电气公司的 Lightspeed 16 层 CT 扫描仪获取 Quasar 呼吸体模的 4D-CT 成像数据，同时体模再现患者特定的呼吸轨迹。在 acquired images 中，在 Pinnacle 治疗计划系统中创建了具有不同复杂程度的无滤过板（FFF）双弧 VMAT 治疗计划，这些复杂程度由调制复杂度评分来描述。使用 Elekta Versa HD 直线加速器在呼吸体模内的 GafChromic EBT3 胶片上进行静态和动态测量。治疗方案为每个部分 10 Gy，共 5 个部分。使用 Radiological Imaging Technology（RIT）软件比较计划剂量分布和实际剂量分布。
对于所研究的运动幅度和周期，相互作用效应对 GTV 覆盖率的影响可以忽略不计。在计划剂量分布和实际剂量分布之间，平均剂量偏差从未低于 -2.00%，并且在单个部分观察到最小剂量差异为 -5.05%。然而，对于 2cm 的振幅，在增加复杂性水平时，在 PTV 的边缘附近，剂量误差可能高达 20.00%。此外，调制复杂度评分能够提供与剂量分布相关的信息。在 GTV 覆盖率方面，复杂度评分和伽马通过率之间观察到 0.65 的相关值（R）。
正如预期的那样，呼吸运动效应对于大振幅呼吸、复杂的场和小的场边缘最为明显。然而，在所有测试条件下，靶区覆盖率均得到维持。
