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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.

该研究的目的是开发一种使用蒙特卡罗模拟的光子/电子传输的高速计算方法。对象描述对于有效执行光子传输非常重要。为了描述对象，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，这三种方法都存在一些缺点（例如边界的准确性、计算时间、内存量、手动指令）。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传输中。物体的表示可以产生每种介质的精确边界，并快速计算光子传输，其精度与使用最精细体素的 VB 方法相同。而且，任何物体的八叉树结构都可以系统地形成。我们的蒙特卡洛代码首先通过读取“八叉树串”来建立模拟几何结构，“八叉树串”是通过在模拟之前自动将物体的一组串行部分形成八叉树结构而产生的，然后在几何结构中传输光子。使用该代码，如果用户只需为想要模拟光子轨迹的物体准备一组连续截面，则可以使用八叉树表示简化的次优几何结构自动执行模拟，而无需手写形成最优几何结构。我们的代码的准确性和能力分别通过与电子伽玛喷淋代码系统（EGS4）的比较和使用头部模型的模拟得到了证实。此外，我们通过比较 VB 方法的结果，使用 Zubal 的数字模型（头部和胸部）检查了我们的代码。综上所述，所提出的方法在任何对象的蒙特卡罗模拟中都是有效的。