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数字几何的研究及其在医学可视化中的应用
何晖光
学位类型工学博士
导师田捷
2002-03-01
学位授予单位中国科学院研究生院
学位授予地点中国科学院自动化研究所
学位专业模式识别与智能系统
关键词三维医学影像 医学影像可视化 数字几何处理 分割 三维重建 化简 细分 平滑 3d Medical Imaging Medical Imaging Visualization Mesh Simplification 3d Rcconstruction Mesh Simplification Subdivision Smooth
摘要现代医学影像技术的进步为医学影像可视化技术的研究和发展提供了必要 的物质基础。今天,可视化技术已经广泛的应用于临床医疗诊断、医学教学研究 巾。以上应用中的核心技术是将过去人眼不能直接看见的人体器官以二维图像形 式或重建出三维模型的形式显示出米。由于三维医学图像建模涉及的数据量大、 体元造型算法复杂、运算量大,因此至今仍是医学图像可视化技术巾的难点所在。 本文工作的丰要基础是我们实验室开发具有自主知识产权的基于微机的三 维医学图像处理与分析系统(3dmed),该系统曾获1999年亚洲CT十大科技进展 前三名。在读博士期间,我作为医学图像小组的组长,参与了其巾很多研究、开 发和管理工作。而本文丰要是将数字几何处理的技术应用在医学影像可视化中, 包括了边缘检测、三维重建、网格化简、细节层次模型与优化等内容,并且所有 的实验均是在我们的系统3dmed上完成的。现将我三年来的主要研究工作归纳 如下: l、提出了一个新的等值面提取算法,它将图像分割与Marching Cube算 法(MC)有机地结合,可采用不同方法对医学图像进行准确分割,避免 了标准MC只适合于阈值分割的局限性,同时采用一种基于区域增长 的方法进行立方体检测。实验表明,该算法的重建速度是标准MC算 法的十倍,而且还可以重建出标准M6’算法无法重建的模型。另外给 出了一个海量数据的重建算法,该算法基于单层表面跟踪,并建立了 缓冲机制,同时采用三角带的数据结构表达三维模型。通过对标准数 据集Visible Man的实验,该算法占用内存为vTK的l/3,其重建速 度比VTK快5~8倍,绘制时间约为原来的1/4。 2、构造了一个基于视点细分的层次细节模型,并将其应用在虚拟内窥镜 中。该算法首先对原始模型层次化简得到基网格,然后通过参数化建 立原始网格与基网格之问的映射关系,并采取与视点相关的细分来重 采样。在视点原则的实现过程中,我们通过八叉树建立了视点变化的 索引,并利用了动态变化的相邻模型问的可重用性。实验表明,该算 法效率高、数据结构简单、易于实现,其速度比Hoppe的VDPM算法快200倍以上,可以满足虚拟内窥镜实时绘制的要求。 3、提出了一个基于距离场的保持特征的网格平滑算法,该算法首先求出 每个点到其邻域的平均平面的距离并构建出距离场,然后对距离场进 行均衡化处理,使顶点沿着法向量移动,同时在进行网格平滑的过程 中,我们通过曲率估计对顶点进行分类。实验表明该算法可以有效的 避免了切
其他摘要Three-dimensional medical visualization technique has been widely used in the fields of medical diagnosis, research and teaching. It made the dream of visualizing noninvasively human internal organs in their true shape and form become true. Since the data of 3D imaging is of large size and the reconstruction is time consuming, 3D reconstruction and 3D rendering are the key technology and difficult points. My dissertation was mostly based on 3D Medical Image Processing and Analyzing System (3dmed), which our lab has succeeded in developing it firstly in China with our own property right. In 1999, 3dmed gained the top three awards of "Asian Major 10 CT Scientific and Technological Advances". During the three years of doctoral work, as the project manager of Medical Image Processing Group, I attend a lot of research, development and management work.' In this paper, the digital geometry processing tools were applied to the medical imaging visualization, which includes edge detection, 3D reconstruction, mesh simplification, level of details and mesh optimization etc, and all the experiments were implemented in the 3dmed system. I summarize my three years research work in this paper. The main work of my dissertation is as follows: 1.A new surface generation scheme was proposed, which integrates segmentation and Marching Cubes algorithm. An appropriate segmentation method was applied to the image sequence according to the feature of the original medical image, and then the segmentation result (binary image data set) was used as the input of MC to generate iso-surfaces. In addition, we develop a surface-tracking algorithm based on region growing, which improve the efficiency by avoiding detecting empty space. The experiments show that the reconstructing speed is as ten times fast as the speed of standard MC, and it can reconstruct the 3D model which the standard MC can't. Another reconstruction of huge datasets was proposed, which is based on single surface tracking. We set up the caching mechanism and use triangle strip to represent the 3D model. We use the Visible Man dataset to do the experiments, and the results show that our method need less memory (just 1/3 of VTK), and the reconstructing speed is as 5-8 times fast as VTK, and the rendering time is just 1/4 of VTK. 2.Construct the level of details model with view-dependent subdivision, and apply it to virtual endoscope. First we simplify the mesh in hierarchy to get the base mesh, and then parameterize the mesh to map the original mesh to the base mesh, and use the view-dependent subdivision to resample. In the implementation of the view point principles, we adopt octree to index the change of the view point, and the model can be reused in the dynamic change. The experiments show that our method is efficient and is easy to implemented, and the model can be rendered in real time. The speed of our method is 200 times faster than Hoppe's VDPM, which can meet the requi
馆藏号XWLW664
其他标识符664
语种中文
文献类型学位论文
条目标识符http://ir.ia.ac.cn/handle/173211/5724
专题毕业生_博士学位论文
推荐引用方式
GB/T 7714
何晖光. 数字几何的研究及其在医学可视化中的应用[D]. 中国科学院自动化研究所. 中国科学院研究生院,2002.
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