Department of Radiation Oncology and Therapy, The First Hospital of Jilin University, 130021, Changchun, China.
Jilin Provincial Key Laboratory of Radiation Oncology and Therapy, Department of Radiation Oncology and Therapy, The First Hospital of Jilin University, 130021, Changchun, China.
Strahlenther Onkol. 2022 Aug;198(8):744-751. doi: 10.1007/s00066-022-01940-3. Epub 2022 Apr 29.
The purpose of this study is to investigate the effect of plan complexity on the dosimetry, delivery accuracy, and interplay effect in lung stereotactic body radiation therapy (SBRT) using volumetric modulated arc therapy (VMAT) with 6 MV flattening-filter-free (FFF) beam.
Twenty patients with early stage non-small cell lung cancer were included. For each patient, high-complexity (HC) and low-complexity (LC) three-partial-arc VMAT plans were optimized by adjusting the normal tissue objectives and the maximum monitoring units (MUs) for a Varian TrueBeam linear accelerator (Varian Medical Systems, Palo Alto, CA, USA) using 6 MV FFF beam. The effect of plan complexity was comprehensively evaluated in three aspects: (1) The dosimetric parameters, including CI, D, R, and dose-volume parameters of organs at risk were compared. (2) The delivery accuracy was assessed by pretreatment quality assurance for two groups of plans. (3) The motion-induced dose deviation was evaluated based on point dose measurements near the tumor center by using a programmable phantom. The standard deviation (SD) and maximum dose difference of five measurements were used to quantify the interplay effect.
The dosimetry of HC and LC plans were similar except the CI (1.003 ± 0.032 and 1.026 ± 0.043, p = 0.030) and D to the spinal cord (10.6 ± 3.2 and 9.9 ± 3.0, p = 0.012). The gamma passing rates were significantly higher in LC plans for all arcs (p < 0.001). The SDs of HC and LC plans ranged from 0.5-16.6% and 0.03-2.9%, respectively, under the conditions of one-field, two-field, and three-field delivery for each plan with 0.5, 1, 2, and 3 cm motion amplitudes. The maximum dose differences of HC and LC plans were 34.5% and 9.1%, respectively.
For lung VMAT SBRT, LC plans have a higher delivery accuracy and a lower motion-induced dose deviation with similar dosimetry compared with HC plans.
本研究旨在探讨使用 6MV 兆伏级快速千伏切换（FFF）射线行容积调强弧形治疗（VMAT）治疗立体定向体部放疗（SBRT）时，计划复杂度对剂量学、治疗准确性和内在效应的影响。
纳入 20 例早期非小细胞肺癌患者。为每位患者优化了高复杂度（HC）和低复杂度（LC）三部分弧形 VMAT 计划，通过调整危及器官的正常组织目标和最大监测单位（MU），使用瓦里安 TrueBeam 直线加速器（瓦里安医疗系统，美国加利福尼亚州帕洛阿尔托）行 6MVFFF 射线治疗。从三个方面综合评估计划复杂度的影响：（1）比较两组计划的剂量学参数，包括适形指数（CI）、剂量（D）、靶区体积比（R）和危及器官的剂量体积参数。（2）通过两组计划的治疗前质量保证评估治疗准确性。（3）基于肿瘤中心附近的点剂量测量，使用可编程体模评估运动引起的剂量偏差。采用 5 次测量的标准差（SD）和最大剂量差来量化内在效应。
除 CI（1.003±0.032 和 1.026±0.043，p=0.030）和脊髓剂量（10.6±3.2 和 9.9±3.0，p=0.012）外，HC 和 LC 计划的剂量学参数相似。所有弧形的 LC 计划的伽马通过率显著高于 HC 计划（p<0.001）。对于每个计划，在单野、双野和三野治疗条件下，LC 计划的 SD 分别在 0.5-16.6%和 0.03-2.9%范围内波动，而 HC 计划的 SD 分别在 0.03-18.5%和 0.003-2.3%范围内波动，每个计划的运动幅度分别为 0.5、1、2 和 3cm。HC 和 LC 计划的最大剂量差异分别为 34.5%和 9.1%。
对于肺部 VMAT SBRT，与 HC 计划相比，LC 计划具有更高的治疗准确性和更低的运动引起的剂量偏差，同时具有相似的剂量学参数。
