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虚拟内窥镜关键算法的研究
其他题名Research on the Key Algorithms of Virtual Endoscopy
李光明
学位类型工学博士
导师田捷
2003-05-01
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 虚拟内窥镜 中心路径提取 网格平滑 层次细节模型 网格简化 细分 虚拟漫游 全景映射 3d Medical Imaging Virtual Endoscopy Centerline Extraction Mesh Smoothing Level-of-detail Mesh Simplification Mesh Subdivi
摘要虚拟内窥镜技术是随着医学影像技术、计算机图像处理、计算机图形学以 及虚拟现实等学科的发展而逐步形成的一种交叉技术。与常规内窥镜相比,虚 拟内窥镜是一种完全的无接触式检查手段,它无需往病人体内插入异物,从而 极大地减轻了病人的痛苦,同时还能对常规内窥镜无法检查的区域(如血管等) 进行检查,在医疗诊断及手术上有着重要的意义。 虚拟内窥镜以计算机断层影像数据为信息来源,以医学图像处理与分析技 术为基础,以计算机图形学与虚拟现实技术为工具,以实现非侵入性的在人体 内部漫游,完成对气管、血管、结肠等的检查为目标,从而成为疾病诊断的一 种新手段,也是手术设计和手术施行的新辅助工具。 虚拟内窥镜系统涵盖了医学影像处理的诸多方面,涉及到模式识别、图像 处理、计算机图形学及虚拟现实等领域,是多个学科在医学领域内的交叉。本 文主要内容就在于对虚拟内窥镜系统中几项关键技术的研究,如中心路径自动 提取、光滑表面模型的生成、三维模型的快速绘制、自动以及引导漫游等。本 文的主要贡献可以概括为以下几点: 1.总结了一个完整的虚拟内窥镜的技术框架,包括数据获取、图像分割、中心 路径提取、光滑表面生成、实时绘制、视点控制及虚拟漫游等。分析了其中 的关键技术,并有针对性的在各章中描述了我们的方法。 2.提出了一种新的基于Hessian矩阵的中心路径提取算法。首先对分割结果进 行距离变换;再对距离图上的每一个点通过其二阶导数构建Hessian矩阵, 计算Hessian矩阵的特征值和特征向量,并以此来确定三维距离图的脊线作 为初始路径;然后进行可视性检测,可视球的半径由该点的距离值以及 Hessian矩阵的特征值自适应的确定;最后利用Dijkstra最短路径生成算法得 到中心路径。该算法一方面避免了可视球半径只能根据经验值进行选取的缺 陷;另一方面脊线的提取也避免了可视性检测中对大量无用体素的检测,从 而提高了算法的效率。实验证明,可视性检测的时问比Reliable Path方法可 以缩短2-5倍。 3.提出了一种改进的网格简化算法。该方法一方面将半边数据结构与QEM误 差准则结合起来,利用半边结构在点、线、面邻接关系查询方面的优良特性, 大大提高了网格简化的速度,实验表明初始化速度大约提高1倍,而简化时 间平均提高2-4倍;另一方面针对用Marching Cubes算法重建出的医学模型 的特点,对QEM误差准则进行了改进,
其他摘要Virtual endoscopy is an integration of medical imaging, image processing, computer graphics and virtual reality techniques. It is meaningful for medical diagnosis because compared to traditional fiberopic endoscopy, it is noninvasive, cost-effective, highly ac- curate, and free of risks, easily tolerated by the patient, and furthermore, it can make physicians examine the regions that traditional endoscopy can not reach such as blood vessel. Virtual endoscopy is a new tool for medical diagnosis, surgery planning and opera- tion, which uses 3D medical images as information source, medical image processing and analyzing techniques as basis, computer graphics and virtual reality techniques as implementation tools, and aiming at noninvasive navigation and examination inside hu- man organs such as trachea, blood vessel and colon. Virtual endoscopy is multi-disciplinary, touching on many techniques in medical im- aging, pattern recognition, and computer graphics. This dissertation mainly concentrates on some key techniques in virtual endoscopy, such as centerline extraction, fairing sur- face generation, real time rendering, automatic and guided navigation etc. The contribu- tion of this dissertation is as follows: 1. A generic system framework for virtual endoscopy is proposed, including data aquisi- tion, image segmentation, centerline extraction, surface generation, real time ren- dering, camera control and virtual navigation. We analyzed some key techniques and presented our scheme in the corresponding chapter. 2. A new centerline extraction algorithm based on Hessian matrix was proposed. First, the distance transformation is performed. Then the initial path is obtained by com- puting the eigenvalues and eigenvectors of Hessian matrix. After that, the visibility test with adaptive visibility sphere radius, which is determined by the eigenvalues of Hessian matrix, is performed to remove useless voxels in the centerline. Finally, the path, with all the points staying away from the surface, is generated by Dijkstra's shortest path algorithm. Our method has two advantages. The first is that the visibility sphere radius is adaptive, not user-defined. The second is that the ridge extraction avoids the test to the large amount of useless voxels in the visibility test procedure. Experiments proved that the time cost in visibility test is 2-5 times less than Reliable Path method. 3. A fast mesh simplification algorithm combining half-edge data structure and modified quadric error metric (QEM) was presented. When half-edge structure is used, the adjacency queries between components of the mesh, such as vertices, faces and edges, can be quickly achieved and thus the run time is reduced remarkably. Ex- periments show that the initialization speed is 2 times as fast as QEM, and the; sim- plification speed is 2-4 times as fast as Q
馆藏号XWLW745
其他标识符745
语种中文
文献类型学位论文
条目标识符http://ir.ia.ac.cn/handle/173211/5762
专题毕业生_博士学位论文
推荐引用方式
GB/T 7714
李光明. 虚拟内窥镜关键算法的研究[D]. 中国科学院自动化研究所. 中国科学院研究生院,2003.
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