A modular method to handle multiple time-dependent quantities in Monte Carlo simulations.
A modular method to handle multiple time-dependent quantities in Monte Carlo simulations.
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DOI：
10.1088/0031-9155/57/11/3295
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发表时间：
2012-06-07
影响因子：
3.5
通讯作者：
Faddegon BA
中科院分区：
文献类型：
--
作者：
Shin J;Perl J;Schümann J;Paganetti H;Faddegon BA
开发了一种用于处理Monte Carlo模拟中的时间依赖量的通用方法，以使此类模拟更易于医学界用于放射治疗中的广泛应用，包括通量和剂量计算。为了以最一般的方式描述时间相关的变化，我们开发了一种函数语法，我们称之为“时间特征”。当模拟量，例如几何对象的位置、角度、磁场、电流等，从时间特征中获取其值，该量随时间而变化。时间相关模拟的操作被分成不同的部分：序列以相等的增量顺序采样时间值，或者从均匀分布中随机采样时间值（允许量在时间上连续变化），然后根据其时间特征计算每个时间相关量。由于这种模块化结构，即使在存在多个时间相关量的情况下，也可以在具有任何给定时间分辨率的单个仿真中有效地执行时间相关仿真。这种方法已经在TOPAS（TOol for PArticle Simulation）中实现，旨在使临床和研究物理学家更容易使用Geant 4进行Monte Carlo模拟。为了证明该方法，模拟了三种临床情况：用于验证加州大学的Crocker实验室眼治疗设施的布拉格峰的恒定性的可变水柱，马萨诸塞州综合医院（MGH）的无源射束散射系统的双散射治疗模式，其中伴随射束电流调制的旋转范围调制器轮（RMW）产生展开的布拉格峰，在MGH的扫描模式中，与时间相关的脉冲形状、能量分布和磁场控制布拉格峰位置。结果证实了该方法的临床适用性。
A general method for handling time-dependent quantities in Monte Carlo simulations was developed to make such simulations more accessible to the medical community for a wide range of applications in radiotherapy, including fluence and dose calculation. To describe time-dependent changes in the most general way, we developed a grammar of functions that we call “Time Features”. When a simulation quantity, such as the position of a geometrical object, an angle, a magnetic field, a current, etc., takes its value from a Time Feature, that quantity varies over time. The operation of time-dependent simulation was separated into distinct parts: the Sequence samples time values either sequentially at equal increments or randomly from a uniform distribution (allowing quantities to vary continuously in time), then each time-dependent quantity is calculated according to its Time Feature. Due to this modular structure, time-dependent simulations, even in the presence of multiple time-dependent quantities, can be efficiently performed in a single simulation with any given time resolution. This approach has been implemented in TOPAS (TOol for PArticle Simulation), designed to make Monte Carlo simulations with Geant4 more accessible to both clinical and research physicists. To demonstrate the method, three clinical situations were simulated: a variable water column used to verify constancy of the Bragg peak of the Crocker Lab eye treatment facility of the University of California, the double-scattering treatment mode of the passive beam scattering system at Massachusetts General Hospital (MGH), where a spinning range modulator wheel (RMW) accompanied by beam current modulation produces a spread-out Bragg Peak, and the scanning mode at MGH, where time-dependent pulse shape, energy distribution and magnetic fields control Bragg peak positions. Results confirm the clinical applicability of the method.
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影响因子：
3.8
作者：
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通讯作者：
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