Department of Radiation Medicine, Roswell Park Comprehensive Cancer Center, Buffalo, New York, USA.
Medical Physics Program, University at Buffalo (SUNY), Buffalo, New York, USA.
J Appl Clin Med Phys. 2023 Oct;24(10):e14063. doi: 10.1002/acm2.14063. Epub 2023 Jul 19.
To use the open-source Monte Carlo (MC) software calculations for TPS monitor unit verification of VMAT plans, delivered with the Varian TrueBeam linear accelerator, and compare the results with a commercial software product, following the guidelines set in AAPM Task Group 219. The TrueBeam is modeled in EGSnrc using the Varian-provided phase-space files. Thirteen VMAT TrueBeam treatment plans representing various anatomical regions were evaluated, comprising 37 treatment arcs. VMAT plans simulations were performed on a computing cluster, using 10 -10 particle histories per arc. Point dose differences at five reference points per arc were compared between Eclipse, MC, and the commercial software, MUCheck. MC simulation with 5 × 10 histories per arc offered good agreement with Eclipse and a reasonable average calculation time of 9-18 min per full plan. The average absolute difference was 3.0%, with only 22% of all points exceeding the 5% action limit. In contrast, the MUCheck average absolute difference was 8.4%, with 60% of points exceeding the 5% dose difference. Lung plans were particularly problematic for MUCheck, with an average absolute difference of approximately 16%. Our EGSnrc-based MC framework can be used for the MU verification of VMAT plans calculated for the Varian TrueBeam; furthermore, our phase space approach can be adapted to other treatment devices by using appropriate phase space files. The use of 5 × 10 histories consistently satisfied the 5% action limit across all plan types for the majority of points, performing significantly better than a commercial MU verification system, MUCheck. As faster processors and cloud computing facilities become even more widely available, this approach can be readily implemented in clinical settings.
为了使用开源蒙特卡罗（MC）软件对瓦里安 TrueBeam 线性加速器提供的 VMAT 计划进行 TPS 监测单位验证，并根据 AAPM Task Group 219 设定的准则将结果与商业软件产品进行比较，我们采用 EGSnrc 对 TrueBeam 进行建模，使用的是瓦里安提供的相空间文件。我们评估了 13 个代表不同解剖区域的 VMAT TrueBeam 治疗计划，共包含 37 个治疗弧。使用计算集群对 VMAT 计划进行模拟，每个弧使用 10-10 个粒子历史。在每个弧的五个参考点处比较 Eclipse、MC 和商业软件 MUCheck 的点剂量差异。每个弧使用 5×10 个历史的 MC 模拟与 Eclipse 吻合较好，且每个完整计划的平均计算时间合理，为 9-18 分钟。平均绝对差异为 3.0%，只有 22%的点超过 5%的作用限。相比之下，MUCheck 的平均绝对差异为 8.4%，60%的点超过 5%的剂量差异。对于 MUCheck，肺部计划是特别成问题的，平均绝对差异约为 16%。我们基于 EGSnrc 的 MC 框架可用于验证为瓦里安 TrueBeam 计算的 VMAT 计划的 MU；此外，我们的相空间方法可以通过使用适当的相空间文件来适应其他治疗设备。对于大多数点，使用 5×10 个历史可以始终满足所有计划类型的 5%作用限，其性能明显优于商业 MU 验证系统 MUCheck。随着更快的处理器和云计算设施变得更加广泛可用，这种方法可以在临床环境中得到很好的应用。
