基于蒙特卡罗的、针对患者的 RapidArc QA 使用 Linac 日志文件。
Monte Carlo based, patient-specific RapidArc QA using Linac log files.
机构信息
Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
出版信息
Med Phys. 2010 Jan;37(1):116-23. doi: 10.1118/1.3266821.
PURPOSE
A Monte Carlo (MC) based QA process to validate the dynamic beam delivery accuracy for Varian RapidArc (Varian Medical Systems, Palo Alto, CA) using Linac delivery log files (DynaLog) is presented. Using DynaLog file analysis and MC simulations, the goal of this article is to (a) confirm that adequate sampling is used in the RapidArc optimization algorithm (177 static gantry angles) and (b) to assess the physical machine performance [gantry angle and monitor unit (MU) delivery accuracy].
METHODS
Ten clinically acceptable RapidArc treatment plans were generated for various tumor sites and delivered to a water-equivalent cylindrical phantom on the treatment unit. Three Monte Carlo simulations were performed to calculate dose to the CT phantom image set: (a) One using a series of static gantry angles defined by 177 control points with treatment planning system (TPS) MLC control files (planning files), (b) one using continuous gantry rotation with TPS generated MLC control files, and (c) one using continuous gantry rotation with actual Linac delivery log files. Monte Carlo simulated dose distributions are compared to both ionization chamber point measurements and with RapidArc TPS calculated doses. The 3D dose distributions were compared using a 3D gamma-factor analysis, employing a 3%/3 mm distance-to-agreement criterion.
RESULTS
The dose difference between MC simulations, TPS, and ionization chamber point measurements was less than 2.1%. For all plans, the MC calculated 3D dose distributions agreed well with the TPS calculated doses (gamma-factor values were less than 1 for more than 95% of the points considered). Machine performance QA was supplemented with an extensive DynaLog file analysis. A DynaLog file analysis showed that leaf position errors were less than 1 mm for 94% of the time and there were no leaf errors greater than 2.5 mm. The mean standard deviation in MU and gantry angle were 0.052 MU and 0.355 degrees, respectively, for the ten cases analyzed.
CONCLUSIONS
The accuracy and flexibility of the Monte Carlo based RapidArc QA system were demonstrated. Good machine performance and accurate dose distribution delivery of RapidArc plans were observed. The sampling used in the TPS optimization algorithm was found to be adequate.
目的
本文提出了一种基于蒙特卡罗（MC）的质量保证（QA）过程，用于使用瓦里安直线加速器（Varian Medical Systems，加利福尼亚州帕洛阿尔托）的 Linac 输送日志文件（DynaLog）验证瓦里安 RapidArc 的动态束输送精度。通过 DynaLog 文件分析和 MC 模拟，本文的目的是：（a）确认 RapidArc 优化算法（177 个静态机架角度）中使用了足够的采样；（b）评估物理机器性能[机架角度和监视器单元（MU）输送精度]。
方法
为各种肿瘤部位生成了 10 个临床可接受的 RapidArc 治疗计划，并在治疗单元上的水等效圆柱体模体上进行了输送。进行了三次 MC 模拟，以计算 CT 体模图像集的剂量：（a）使用由 177 个控制点定义的一系列静态机架角度，每个控制点都有治疗计划系统（TPS）多叶准直器控制文件（规划文件）；（b）使用 TPS 生成的多叶准直器控制文件进行连续机架旋转；（c）使用实际的直线加速器输送日志文件进行连续机架旋转。MC 模拟剂量分布与电离室点测量和 RapidArc TPS 计算剂量进行了比较。使用三维伽玛因子分析比较三维剂量分布，采用 3%/3mm 距离一致性标准。
结果
MC 模拟、TPS 和电离室点测量之间的剂量差异小于 2.1%。对于所有计划，MC 计算的三维剂量分布与 TPS 计算的剂量吻合良好（考虑到的超过 95%的点的伽玛因子值小于 1）。机器性能 QA 还辅以广泛的 DynaLog 文件分析。DynaLog 文件分析表明，叶片位置误差在 94%的时间内小于 1mm，并且没有叶片误差大于 2.5mm。分析的十个病例中，MU 和机架角度的平均值标准偏差分别为 0.052MU 和 0.355 度。
结论
证明了基于 MC 的 RapidArc QA 系统的准确性和灵活性。观察到 RapidArc 计划的机器性能良好，剂量分布输送准确。TPS 优化算法中使用的采样被认为是足够的。
Zotero 插件