BC Cancer Agency - Vancouver Centre.
J Appl Clin Med Phys. 2014 May 8;15(3):4686. doi: 10.1120/jacmp.v15i3.4686.
A Monte Carlo (MC) validation of the vendor-supplied Varian TrueBeam 6 MV flattened (6X) phase-space file and the first implementation of the Siebers-Keall MC MLC model as applied to the HD120 MLC (for 6X flat and 6X flattening filter-free (6X FFF) beams) are described. The MC model is validated in the context of VMAT patient-specific quality assurance. The Monte Carlo commissioning process involves: 1) validating the calculated open-field percentage depth doses (PDDs), profiles, and output factors (OF), 2) adapting the Siebers-Keall MLC model to match the new HD120-MLC geometry and material composition, 3) determining the absolute dose conversion factor for the MC calculation, and 4) validating this entire linac/MLC in the context of dose calculation verification for clinical VMAT plans. MC PDDs for the 6X beams agree with the measured data to within 2.0% for field sizes ranging from 2 × 2 to 40 × 40 cm2. Measured and MC profiles show agreement in the 50% field width and the 80%-20% penumbra region to within 1.3 mm for all square field sizes. MC OFs for the 2 to 40 cm2 square fields agree with measurement to within 1.6%. Verification of VMAT SABR lung, liver, and vertebra plans demonstrate that measured and MC ion chamber doses agree within 0.6% for the 6X beam and within 2.0% for the 6X FFF beam. A 3D gamma factor analysis demonstrates that for the 6X beam, > 99% of voxels meet the pass criteria (3%/3 mm). For the 6X FFF beam, > 94% of voxels meet this criteria. The TrueBeam accelerator delivering 6X and 6X FFF beams with the HD120 MLC can be modeled in Monte Carlo to provide an independent 3D dose calculation for clinical VMAT plans. This quality assurance tool has been used clinically to verify over 140 6X and 16 6X FFF TrueBeam treatment plans.
描述了一种对瓦里安 TrueBeam 6 MV 平坦化（6X）相空间文件的供应商提供的文件以及 Siebers-Keall MC 多叶准直器（MLC）模型的首次实现（适用于 HD120 MLC，用于 6X 平坦化和 6X 无过滤平坦化（6X FFF）射束）的蒙特卡罗（MC）验证。MC 模型在 VMAT 患者特定质量保证的背景下进行了验证。MC 委托过程包括：1）验证计算出的开放野百分深度剂量（PDD）、轮廓和输出因子（OF），2）调整 Siebers-Keall MLC 模型以匹配新的 HD120-MLC 几何形状和材料组成，3）确定 MC 计算的绝对剂量转换因子，以及 4）在临床 VMAT 计划剂量计算验证的背景下验证整个直线加速器/MLC。6X 射束的 MC PDD 与测量数据的偏差在 2%以内，适用于 2×2 至 40×40cm2 的射野尺寸。所有方形射野尺寸的 50%射野宽度和 80%-20%半影区域的测量和 MC 轮廓均在 1.3mm 以内。2 至 40cm2 方形射野的 MC OF 与测量值的偏差在 1.6%以内。验证 VMAT SABR 肺、肝和椎骨计划表明，6X 射束的测量和 MC 离子室剂量的偏差在 0.6%以内，6X FFF 射束的偏差在 2.0%以内。三维伽马因子分析表明，对于 6X 射束，>99%的体素符合通过标准（3%/3mm）。对于 6X FFF 射束，>94%的体素符合该标准。配备 HD120 MLC 的 TrueBeam 加速器可对 6X 和 6X FFF 射束进行 MC 建模，为临床 VMAT 计划提供独立的三维剂量计算。该质量保证工具已在临床上用于验证超过 140 个 6X 和 16 个 6X FFF TrueBeam 治疗计划。
