Volume-based geometric modeling for radiation transport calculations.
Volume-based geometric modeling for radiation transport calculations.
复制标题
用于辐射传输计算的基于体积的几何建模。
DOI：
10.1118/1.596810
复制
发表时间：
1992
期刊：
影响因子：
3.8
通讯作者：
Williamson,JF
中科院分区：
文献类型：
--
作者：
Li,Z;Williamson,JF
辐射场的精确理论表征对于设计复杂的系统，如直线加速器和腔内照射器，以及产生实验测量无法获得的基本剂量计算数据是一个有价值的工具。这类问题的蒙特卡罗和确定性解决方案都需要一个系统来精确建模复杂的3-D几何图形，该系统支持光线跟踪、点和线段分类以及2-D图形表示。以前的实体建模组合方法涉及将复杂结构描述为简单对象的集合论组合，但它们的易用性受到限制，并且对对象之间的几何关系施加了不现实的约束，例如排除公共边界。开发了一种新的基于体积的实体建模方法，该方法基于对区域边界、内部和外部的拓扑一致的定义。根据这些定义，FORTRAN并集、交集和差分例程被开发出来，允许将渐开线和深度嵌套的结构描述为适应共享边界的椭球体、椭圆柱体、棱柱体、圆锥体和平面的集合论组合。通过一种新的排序算法将轨迹上相邻交点之间的线段分配到适当的区域，该算法是对Siddon方法的推广。开发了两个二维图形显示工具，以帮助调试给定的几何模型。文中描述了该系统的数学基础，并与其他方法进行了比较，并讨论了实例。
Accurate theoretical characterization of radiation fields is a valuable tool in the design of complex systems, such as linac heads and intracavitary applicators, and for generation of basic dose calculation data that is inaccessible to experimental measurement. Both Monte Carlo and deterministic solutions to such problems require a system for accurately modeling complex 3‐D geometries that supports ray tracing, point and segment classification, and 2‐D graphical representation. Previous combinatorial approaches to solid modeling, which involve describing complex structures as set‐theoretic combinations of simple objects, are limited in their ease of use and place unrealistic constraints on the geometric relations between objects such as excluding common boundaries. A new approach to volume‐based solid modeling has been developed which is based upon topologically consistent definitions of boundary, interior, and exterior of a region. From these definitions, FORTRAN union, intersection, and difference routines have been developed that allow involuted and deeply nested structures to be described as set‐theoretic combinations of ellipsoids, elliptic cylinders, prisms, cones, and planes that accommodate shared boundaries. Line segments between adjacent intersections on a trajectory are assigned to the appropriate region by a novel sorting algorithm that generalizes upon Siddon's approach. Two 2‐D graphic display tools are developed to help the debugging of a given geometric model. In this paper, the mathematical basis of our system is described, it is contrasted to other approaches, and examples are discussed.