Development of a virtual source model for Monte Carlo-based independent dose calculation for varian linac.
Development of a virtual source model for Monte Carlo-based independent dose calculation for varian linac.
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DOI：
10.1002/acm2.13556
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发表时间：
2022-05
影响因子：
2.1
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中科院分区：
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蒙特卡罗（MC）独立剂量计算通常基于相空间文件（PSF），因为它们可以准确地表示粒子特征。 PSF 通常很大，会造成计算时间的瓶颈。此外，独立粒子的数量受到 PSF 的限制，从而阻止了统计不确定性的进一步降低。本研究的目的是开发和验证虚拟源模型 (VSM) 以解决这些限制。对瓦里安 TrueBeam 医用直线加速器 6X、6XFFF、10X 和 10XFFF 光束配置的现有 PSF 中的粒子进行统计、分析，并用于生成包含电子污染的双源光子 VSM。计算了颗粒密度分布、动能谱、颗粒方向以及特性之间的相关性。每个光束配置的 VSM 模型均通过水体模测量以及针对原始 PSF 的临床测试用例进行了验证。新的 VSM 为每个波束配置需要 67 MB 的磁盘空间，而它们所基于的 PSF 则需要 50 GB 的磁盘空间，并且有效地消除了 PSF 设置的瓶颈。在 MC 不确定性为 3% 时，VSM 方法将我们服务器上的计算时间减少了 14 倍。将使用 VSM 方法获得的 MC 剂量与临床测试案例中 PSF 生成的剂量进行比较，并使用伽马指数分析在水体模中进行测量。对于所有测试，VSM 与 PSF 剂量和测量结果非常一致（剂量和测量结果之间通过的体素>90%）。这项研究的结果表明，瓦里安直线加速器的 VSM 模型的成功推导和实现，显着节省了计算时间，而无需牺牲独立剂量计算的准确性。
Monte Carlo (MC) independent dose calculations are often based on phase‐space files (PSF), as they can accurately represent particle characteristics. PSF generally are large and create a bottleneck in computation time. In addition, the number of independent particles is limited by the PSF, preventing further reduction of statistical uncertainty. The purpose of this study is to develop and validate a virtual source model (VSM) to address these limitations. Particles from existing PSF for the Varian TrueBeam medical linear accelerator 6X, 6XFFF, 10X, and 10XFFF beam configurations were tallied, analyzed, and used to generate a dual‐source photon VSM that includes electron contamination. The particle density distribution, kinetic energy spectrum, particle direction, and the correlations between characteristics were computed. The VSM models for each beam configuration were validated with water phantom measurements as well as clinical test cases against the original PSF. The new VSM requires 67 MB of disk space for each beam configuration, compared to 50 GB for the PSF from which they are based and effectively remove the bottleneck set by the PSF. At 3% MC uncertainty, the VSM approach reduces the calculation time by a factor of 14 on our server. MC doses obtained using the VSM approach were compared against PSF‐generated doses in clinical test cases and measurements in a water phantom using a gamma index analysis. For all tests, the VSMs were in excellent agreement with PSF doses and measurements (>90% passing voxels between doses and measurements). Results of this study indicate the successful derivation and implementation of a VSM model for Varian Linac that significantly saves computation time without sacrificing accuracy for independent dose calculation.