Perl J, Shin J, Schuemann J, Faddegon B, Paganetti H
SLAC National Accelerator Laboratory, Menlo Park, CA.
UCSF, San Francisco, CA.
Med Phys. 2012 Jun;39(6Part17):3814. doi: 10.1118/1.4735562.
The TOPAS Tool for Particle Simulation was developed to make Geant4 Monte Carlo simulation more readily available for research and clinical physicists. Before releasing this new tool to the proton therapy community, several test have been performed to ensure accurate simulations in a variety of proton therapy setups.
TOPAS can model a passive scattering or scanning beam treatment head, model a patient geometry based on CT images, score dose, fluence, etc., save and replay a phase space, provides advanced graphics, and is fully four-dimensional (4D) to handle variations in beam delivery and patient geometry during treatment. An innovative control system meets requirements for ease of use, reliability and repeatability without sacrificing flexibility. To test the TOPAS code, we modeled proton therapy treatment examples including the UCSF eye treatment beamline (UCSFETB), the MGH STAR radiosurgery beamline and the MGH gantry treatment head in passive scattering and scanning modes. The simulations included time-dependent geometry and time- dependent beam current delivery.
At the UCSFETB, time- dependent depth dose distributions were accurately simulated with time- varying energy modulation from a rotating propeller. At the MGH STAR beamline, distal and proximal ranges agreed within measurement uncertainty and the shape of the simulated SOBP followed measured data. For the MGH gantry treatment head in passive scattering mode, SOBPs were simulated for the full set of range modulator wheel and second scatterer combinations. TOPAS simulation was within clinical required accuracy. For the MGH nozzle in scanning mode, a variety of scan patterns were simulated with fluence maps generated for cases including beam current modulation, energy modulation and target tracking.
Our results demonstrate the functionality of TOPAS. They show agreement with measured data and demonstrate the capabilities of TOPAS in simulating beam delivery in 3D and 4D. This work was supported by IH/NCI under R01 CA 140735-01.
开发TOPAS粒子模拟工具是为了让研究人员和临床物理学家更易于使用Geant4蒙特卡罗模拟。在将这个新工具发布到质子治疗领域之前，已经进行了多项测试，以确保在各种质子治疗设置中进行准确的模拟。
TOPAS可以对被动散射或扫描束治疗头进行建模，基于CT图像对患者几何结构进行建模，对剂量、注量等进行评分，保存和重放相空间，提供高级图形，并且是完全四维（4D）的，以处理治疗过程中束流传输和患者几何结构的变化。一个创新的控制系统满足了易用性、可靠性和可重复性的要求，同时又不牺牲灵活性。为了测试TOPAS代码，我们对质子治疗的示例进行了建模，包括加州大学旧金山分校眼部治疗束线（UCSFETB）、麻省总医院（MGH）立体定向放射治疗束线以及MGH被动散射和扫描模式下的龙门治疗头。模拟包括随时间变化的几何结构和随时间变化的束流传输。
在UCSFETB，通过旋转螺旋桨随时间变化的能量调制，准确模拟了随时间变化的深度剂量分布。在MGH STAR束线，远端和近端射程在测量不确定度范围内一致，模拟的剂量建成区（SOBP）形状与测量数据相符。对于被动散射模式下的MGH龙门治疗头，针对全套射程调制轮和第二散射体组合模拟了SOBP。TOPAS模拟在临床要求的精度范围内。对于扫描模式下的MGH喷嘴，模拟了各种扫描模式，并针对包括束流调制、能量调制和靶点跟踪的情况生成了注量图。
我们的结果展示了TOPAS的功能。它们与测量数据相符，并证明TOPAS在模拟三维和四维束流传输方面的能力。这项工作得到了美国国立卫生研究院（NIH）/美国国立癌症研究所（NCI）根据R01 CA 140735 - 01提供的支持。
