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Accelerating photon transport in Monte Carlo simulation using octree structure

使用八叉树结构加速蒙特卡罗模拟中的光子传输

基本信息

批准号：
07457204
负责人：
OGAWA Koichi
金额：
$ 3.07万
依托单位：
Hosei University, College of Engineering
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07457204/
关键词：
Monte Carlo simulation Photon transport Object modeling Octree coding Single photon emission CT Acceleration Radiology Image Processing オクトツリーモンテカルロ計算放射線治療 SPECT PET 核医学

项目摘要

The study was carried out to develop a high-speed calculation method in photon/electron transportation using a Monte Carlo simulation. Object description is important in performing the photon transport efficiently. In order to describe an object, three methods have been proposed : a shape-based (SV) approach, a voxel-based (VB) approach, and a solid geometry based approach. However, these three methods have some shortcoming (e.g., accuracy of boundaries, calculation time, amount of memory, manual instructions). To the problems we introduced an octree representation of an object to the photon transport using a Monte Carlo method. The representation of the object yields accurate boundaries of each medium and fast calculation of the photon transport with the same accuracy as the VB method using the finest voxels. Moreover, the octree structure for any object can be formed systematically.Our Monte Carlo code, first, establishes the simulation geometry by reading "octree string, " which is produced by forming an octree structure from a set of serial sections for the object before the simulation automatically, and then it transports photons in the geotry. Using the code, if the user just prepares a set of serial sections for the object in which he wants to simulate photon trajectories, he can perform the simulation automatically using the suboptimal geometry simplified by the octree representation without forming the optimal geometry by handwriting. The accuracy and ability of our code were confirmed by comparison with Electron Gamma Shower code system (EGS4) and simulations using a head phantom, respectively. Moreover, we examined our code using Zubal's digital phantoms (head and thorax) by comparing the results of the VB approach. In summary, the proposed method is efficient in the Monte Carlo simulation of any object.

本研究旨在发展一种基于蒙特卡罗模拟的快速计算光子/电子输运的方法。物体描述对于有效地执行光子传输是重要的。为了描述物体，已经提出了三种方法：基于形状(SV)的方法、基于体素(VB)的方法和基于实体几何的方法。然而，这三种方法都有一些缺点(例如，边界的准确性、计算时间、内存量、人工指令)。针对这些问题，我们使用蒙特卡罗方法将物体的八叉树表示引入到光子输运中。对象的表示生成每个介质的准确边界，并以与使用最精细体素的VB方法相同的精度快速计算光子传输。我们的蒙特卡罗代码首先通过读取“八叉树字符串”来建立模拟几何，该字符串是在模拟前自动地从对象的一组连续截面形成一个八叉树结构，然后它在大地中传输光子。使用该代码，如果用户只是为他想要在其中模拟光子轨迹的对象准备一组连续的部分，他可以使用由八叉树表示简化的次优几何来自动执行模拟，而不需要手写形成最优几何。通过与电子伽玛簇射系统(EGS4)的比较和头模的模拟，验证了该程序的准确性和计算能力。此外，我们使用Zubal的数字体模(头部和胸部)通过比较VB方法的结果来检查我们的代码。综上所述，该方法对任意物体的蒙特卡罗模拟都是有效的。