摘要
随着计算机技术和图形图象学的发展，医学成像技术也不断得到提高。为了满足人们在医疗领域全面了解人体病灶结构信息的需要，医学三维图像重建技术的发展日益显得重要。
本文首先对医学三维图像重建中应用的科学计算可视化理论、方法进行了探讨和综述。分类阐述了医学三维图像重建的几种方法，分析了它们的差异和特点。
在对基于表面重建技术的Marching Cubes(MC)算法的研究中，着重讨论了其中剖分立方体构造等值面的原理，通过算法的实践，掌握其特点。
本文重点讨论了光线投射体绘制技术的原理和所涉及的光照模型、伪彩色、重采样、图像合成等技术。在对该算法实践的基础上，借鉴其他三维图像重建方法，对原算法进行改进。采用绘制物质分界面所在局部区域的方法，即层绘制方法，进行三维图像重建。在加强显示效果的同时，减少运算数据量，提高绘制速度。根据这一思想，设计了两种具体算法，并进行了实验。
实验结果表明，改进后的算法在图像显示效果和处理速度上都较原始算法有所提高。
With the development of computer technology and computer graphics, medical imaging technology has a big improvement. To meet doctors' need
of the detailed information about patient's body, the research on medical
3-D image reconstruction technology has been carried out widely.
In this thesis, the theory and method about visualization in scientific computing are introduced and described. Several 3-D rendering methods and their characters are analyzed.
Marching Cubes, a kind of surface rendering method, is introduced. Through the experiment on this method, the theory about cutting cubes and constructing isovalue surfaces is discussed.
Ray-Casting Volume Rendering and some involved technologies, such as shading model, resampling and mapping, are introduced. A new method is
presented to mend Ray-Casting Volume Rendering. The method is to render
the region with some thickness, which contains the dividing line between tow different matters. Based on this method, there are tow algorithms to be carried out in our experiment. The new method is proved that it is better than old method in rendering speed and image impression.
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