利用 Elekta Agility 160 叶多叶准直器对 VMAT 治疗计划进行蒙特卡罗剂量验证。

Monte Carlo dose verification of VMAT treatment plans using Elekta Agility 160-leaf MLC.

机构信息

Department of Radiological Technology, Yamaguchi University Hospital, 1-1-1 Minamikogushi, Ube 755-8505, Japan.

Department of Health Sciences, Faculty of Life Sciences, Kumamoto University, 4-24-1 Kuhonji, Kumamoto 862-0976, Japan.

出版信息

Phys Med. 2018 Jul;51:22-31. doi: 10.1016/j.ejmp.2018.06.003. Epub 2018 Jun 20.

DOI:10.1016/j.ejmp.2018.06.003

PMID:30278982

Abstract

In this study, we verified volumetric modulated arc therapy (VMAT) plans in an Elekta Synergy system with an integrated Agility 160-leaf multileaf collimator (MLC) by comparing them with Monte Carlo (MC)-calculated dose distributions using the AAPM TG-119 structure sets. The head configuration of the linear accelerator with the integrated MLC was simulated with the EGSnrc/BEAMnrc code. Firstly, the dosimetric properties of the MLC were evaluated with the MC technique and film measurements. Next, VMAT plans were created with the Pinnacle treatment planning system (TPS) for four regions in the AAPM TG-119 structures. They were then verified by comparing them with MC-calculated dose distributions using dose volume histograms (DVHs) and three-dimensional (3D) gamma analysis. The MC simulations for the Agility MLC dosimetric properties were in acceptable agreement with measurements. TPS-VMAT plans using TG-119 structure sets agreed with MC dose distributions within 2% in the comparison of D in planning target volumes (PTVs) evaluated from DVHs. In contrast, higher dose regions such as D, D, and D in PTVs for TPS tended to be smaller than MC values. This tendency was particularly noticeable for mock head and neck with complicated structures. In 3D gamma analysis, the passing rates with 3%/3mm criteria in PTVs were ≥99%, except for mock head and neck (89.5%). All passing rates for organs at risk (OARs) were in acceptable agreement of >96%. It is useful to verify dose distributions of PTVs and OARs in TPS-VMAT plans by using MC dose calculations and 3D gamma analysis.

摘要

在这项研究中，我们通过比较使用 AAPM TG-119 结构集的 MC 计算剂量分布，验证了 Elekta Synergy 系统中带有集成的 Agility 160 叶多叶准直器（MLC）的容积调强弧形治疗（VMAT）计划。使用 EGSnrc/BEAMnrc 代码模拟了带有集成 MLC 的直线加速器的头部结构。首先，使用 MC 技术和胶片测量评估了 MLC 的剂量学特性。接下来，使用 Pinnacle 治疗计划系统（TPS）为 AAPM TG-119 结构中的四个区域创建了 VMAT 计划。然后，通过使用剂量体积直方图（DVH）和三维（3D）伽马分析比较它们与 MC 计算剂量分布，来验证这些计划。对于 Agility MLC 的剂量学特性，MC 模拟与测量结果吻合良好。在比较从 DVH 评估的 PTV 中 D、D 和 D 等计划靶区（PTV）的剂量时，使用 TG-119 结构集的 TPS-VMAT 计划与 MC 剂量分布的差异在 2%以内。相比之下，TPS 中 PTV 中的 D、D 和 D 等高剂量区域的剂量值比 MC 值小。这种趋势在结构复杂的模拟头颈部中尤为明显。在 3D 伽马分析中，除模拟头颈部外（89.5%），PTV 中 3%/3mm 标准的通过率均≥99%。对于危及器官（OARs），所有的通过率均符合>96%的可接受标准。使用 MC 剂量计算和 3D 伽马分析验证 TPS-VMAT 计划中 PTV 和 OAR 的剂量分布是有用的。