Accurate Monte Carlo simulations for nozzle design, commissioning and quality assurance for a proton radiation therapy facility
Accurate Monte Carlo simulations for nozzle design, commissioning and quality assurance for a proton radiation therapy facility
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DOI：
10.1118/1.1762792
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发表时间：
2004-07-01
期刊：
影响因子：
3.8
通讯作者：
Kooy, HM
中科院分区：
文献类型：
--
作者：
Paganetti, H;Jiang, H;Kooy, HM
蒙特卡罗剂量法计算是放射治疗的基本方法。为了充分利用该工具，必须对光束传输系统进行详细的模拟，并且必须准确地知道初始光束参数。光束输送系统本身的建模打开了蒙特卡罗计算证明非常有用的各个领域，例如治疗设施的设计和调试以及质量保证验证。采用genant4.5.2蒙特卡罗代码对美国马萨诸塞州总医院（MGH）东北质子治疗中心（NPTC）的龙门式治疗喷嘴进行了详细建模。为此，人们发现了各种新的解决方案来模拟光束路径中不规则形状的物体，如轮廓散射体、病人孔径或病人补偿器。实现了调制器轮等运动部件在时间和空间上的四维仿真。此外，还定义了质子治疗应用的适当物理模型和截面。我们提出了测量数据和模拟之间的比较。这些结果表明，通过以毫米精度对处理喷嘴进行建模，可以再现测量剂量分布，其范围和调制宽度的精度优于1毫米，在展开布拉格峰（SOBP）的情况下。结果表明，模拟结果可用于生成调试处理计划系统所需的光束数据。利用蒙特卡罗喷嘴模型，从散射辐射和二次辐射两方面对喷嘴进行了力学优化设计。我们对中子背景进行了模拟。此外，蒙特卡罗计算支持调试工作，以了解光束特性的敏感性以及这些特性如何影响剂量。我们提出了水中剂量分布对各种光束参数和几何失调的敏感性。这允许质量保证公差的定义和质量保证程序的设计。(C) 2004年美国医学物理学家协会。
Monte Carlo dosimetry calculations are essential methods in radiation therapy. To take full advantage of this tool, the beam delivery system has to be simulated in detail and the initial beam parameters have to be known accurately. The modeling of the beam delivery system itself opens various areas where Monte Carlo calculations prove extremely helpful, such as for design and commissioning of a therapy facility as well as for quality assurance verification. The gantry treatment nozzles at the Northeast Proton Therapy Center (NPTC) at Massachusetts General Hospital (MGH) were modeled in detail using the GEANT4.5.2 Monte Carlo code. For this purpose, various novel solutions for simulating irregular shaped objects in the beam path, like contoured scatterers, patient apertures or patient compensators, were found. The four-dimensional, in time and space, simulation of moving parts, such as the modulator wheel, was implemented. Further, the appropriate physics models and cross sections for proton therapy applications were defined. We present comparisons between measured data and simulations. These show that by modeling the treatment nozzle with millimeter accuracy, it is possible to reproduce measured dose distributions with an accuracy in range and modulation width, in the case of a spread-out Bragg peak (SOBP), of better than 1 mm. The excellent agreement demonstrates that the simulations can even be used to generate beam data for commissioning treatment planning systems. The Monte Carlo nozzle model was used to study mechanical optimization in terms of scattered radiation and secondary radiation in the design of the nozzles. We present simulations on the neutron background. Further, the Monte Carlo calculations supported commissioning efforts in understanding the sensitivity of beam characteristics and how these influence the dose delivered. We present the sensitivity of dose distributions in water with respect to various beam parameters and geometrical misalignments. This allows the definition of tolerances for quality assurance and the design of quality assurance procedures. (C) 2004 American Association of Physicists in Medicine.