目的探讨三维超声体元模型成像对胃十二指肠疾病的诊断价值。
Objective To evaluate the clinical application of three-dimensional ultrasonographic image in gastroduodenal diseases.
体元模型由块体组成，块体之间界面采用连续函数或离散点插值表示。
The volume element model is composed of blocks, in which the interfaces between blocks represent by continuous function or interpolation at discrete points.
本文基于费马原理，利用全路径迭代算法实现体元模型中的三维VSP两点射线追踪。
Based on Fermat's principle, the paper USES full-path iterative algorithm to realize 3-d VSP two-point ray tracing in volume element model.
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