Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, GA, 30322, USA.
Memorial Sloan Kettering Cancer Center, New York City, NY, 10065, USA.
Med Phys. 2020 Apr;47(4):1545-1557. doi: 10.1002/mp.14021. Epub 2020 Feb 4.
Treatment planning systems (TPSs) from different vendors can involve different implementations of Monte Carlo dose calculation (MCDC) algorithms for pencil beam scanning (PBS) proton therapy. There are currently no guidelines for validating non-water materials in TPSs. Furthermore, PBS-specific parameters can vary by 1-2 orders of magnitude among different treatment delivery systems (TDSs). This paper proposes a standardized framework on the use of commissioning data and steps to validate TDS-specific parameters and TPS-specific heterogeneity modeling to potentially reduce these uncertainties.
A standardized commissioning framework was developed to commission the MCDC algorithms of RayStation 8A and Eclipse AcurosPT v13.7.20 using water and non-water materials. Measurements included Bragg peak depth-dose and lateral spot profiles and scanning field outputs for Varian ProBeam. The phase-space parameters were obtained from in-air measurements and the number of protons per MU from output measurements of 10 × 10 cm square fields at a 2 cm depth. Spot profiles and various PBS field measurements at additional depths were used to validate TPS. Human tissues in TPS, Gammex phantom materials, and artificial materials were used for the TPS benchmark and validation.
The maximum differences of phase parameters, spot sigma, and divergence between MCDC algorithms are below 4.5 µm and 0.26 mrad in air, respectively. Comparing TPS to measurements at depths, both MC algorithms predict the spot sigma within 0.5 mm uncertainty intervals, the resolution of the measurement device. Beam Configuration in AcurosPT is found to underestimate number of protons per MU by ~2.5% and requires user adjustment to match measured data, while RayStation is within 1% of measurements using Auto model. A solid water phantom was used to validate the range accuracy of non-water materials within 1% in AcurosPT.
The proposed standardized commissioning framework can detect potential issues during PBS TPS MCDC commissioning processes, and potentially can shorten commissioning time and improve dosimetric accuracies. Secondary MCDC can be used to identify the root sources of disagreement between primary MCDC and measurement.
来自不同供应商的治疗计划系统（TPS）可能涉及用于笔形束扫描（PBS）质子治疗的蒙特卡罗剂量计算（MCDC）算法的不同实现。目前还没有用于验证 TPS 中非水材料的指南。此外，PBS 特定参数在不同的治疗递送系统（TDS）之间可能相差 1-2 个数量级。本文提出了一个使用调试数据的标准化框架以及验证 TDS 特定参数和 TPS 特定异质性建模的步骤，以潜在地降低这些不确定性。
开发了一个标准化的调试框架，用于使用水和非水材料对 RayStation 8A 和 Eclipse AcurosPT v13.7.20 的 MCDC 算法进行调试。测量包括布拉格峰深度剂量和横向光斑轮廓以及瓦里安 ProBeam 的扫描场输出。相位空间参数是从空气中的测量获得的，质子数是从 2cm 深度处 10×10cm 正方形射野的输出测量中获得的 MU。光斑轮廓和其他深度的各种 PBS 场测量用于验证 TPS。TPS 中的人体组织、Gammex 体模材料和人工材料用于 TPS 基准测试和验证。
在空气中，MCDC 算法之间的相位参数、光斑标准差和发散的最大差异分别小于 4.5µm 和 0.26mrad。将 TPS 与深度处的测量结果进行比较，两个 MC 算法都能在 0.5mm 的测量不确定度范围内预测光斑标准差，这是测量设备的分辨率。在 AcurosPT 中，发现 Beam Configuration 低估了 MU 中的质子数，误差约为 2.5%，需要用户调整以匹配测量数据，而 RayStation 使用 Auto 模型时的误差在 1%以内。使用固体水体模在 AcurosPT 中验证了非水材料的射程精度在 1%以内。
所提出的标准化调试框架可以检测 PBS TPS MCDC 调试过程中的潜在问题，并可能缩短调试时间，提高剂量学精度。二级 MCDC 可用于确定主要 MCDC 和测量之间不一致的根本原因。
