De Beenhouwer Jan, Staelens Steven, Kruecker Dirk, Ferrer Ludovic, D'Asseler Yves, Lemahieu Ignace, Rannou Fernando R
Ghent University, ELIS/MEDISIP, De Pintelaan 185, Block B, B-9000 Ghent, Belgium.
Med Phys. 2007 Jun;34(6):1926-33. doi: 10.1118/1.2731993.
Geometry and tracking (GEANT4) is a Monte Carlo package designed for high energy physics experiments. It is used as the basis layer for Monte Carlo simulations of nuclear medicine acquisition systems in GEANT4 Application for Tomographic Emission (GATE). GATE allows the user to realistically model experiments using accurate physics models and time synchronization for detector movement through a script language contained in a macro file. The downside of this high accuracy is long computation time. This paper describes a platform independent computing approach for running GATE simulations on a cluster of computers in order to reduce the overall simulation time. Our software automatically creates fully resolved, nonparametrized macros accompanied with an on-the-fly generated cluster specific submit file used to launch the simulations. The scalability of GATE simulations on a cluster is investigated for two imaging modalities, positron emission tomography (PET) and single photon emission computed tomography (SPECT). Due to a higher sensitivity, PET simulations are characterized by relatively high data output rates that create rather large output files. SPECT simulations, on the other hand, have lower data output rates but require a long collimator setup time. Both of these characteristics hamper scalability as a function of the number of CPUs. The scalability of PET simulations is improved here by the development of a fast output merger. The scalability of SPECT simulations is improved by greatly reducing the collimator setup time. Accordingly, these two new developments result in higher scalability for both PET and SPECT simulations and reduce the computation time to more practical values.
几何与跟踪（GEANT4）是一个为高能物理实验设计的蒙特卡罗软件包。它被用作GEANT4断层发射应用（GATE）中核医学采集系统蒙特卡罗模拟的基础层。GATE允许用户通过宏文件中包含的脚本语言，使用精确的物理模型和探测器移动的时间同步来逼真地模拟实验。这种高精度的缺点是计算时间长。本文描述了一种平台无关的计算方法，用于在计算机集群上运行GATE模拟，以减少总体模拟时间。我们的软件会自动创建完全解析的、非参数化的宏，并附带一个即时生成的特定于集群的提交文件，用于启动模拟。针对正电子发射断层扫描（PET）和单光子发射计算机断层扫描（SPECT）这两种成像模态，研究了GATE模拟在集群上的可扩展性。由于灵敏度较高，PET模拟的特点是数据输出率相对较高，会生成相当大的输出文件。另一方面，SPECT模拟的数据输出率较低，但需要较长的准直器设置时间。这两个特性都阻碍了作为CPU数量函数的可扩展性。本文通过开发一种快速输出合并器来提高PET模拟的可扩展性。通过大幅减少准直器设置时间来提高SPECT模拟的可扩展性。因此，这两项新进展提高了PET和SPECT模拟的可扩展性，并将计算时间减少到更实际的值。
