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Alternative TitleResearch on and Construction of Virtual Endoscopy System
Thesis Advisor卢汉清
Degree Grantor中国科学院自动化研究所
Place of Conferral中国科学院自动化研究所
Degree Discipline模式识别与智能系统
Abstract随着医学成像技术的进步以及虚拟现实和图形学等技术的发展,计算机辅助 治疗正成为研究的热点。虚拟内窥镜技术(Virtual Endoscopy)的产生正基于此。 内窥镜检查是一种常用的医学检查手段。虚拟内窥镜则是基于医学成像技术,如 CT、MRI等,利用图形学等技术对真实内窥镜的一种模拟。和真实内窥镜相比, 虚拟内窥镜检查耗时短、花费小,且是非侵入式的,可以将检查的风险降低到最 小。因此可以在某些应用上替代真实内窥镜。 根据所采用的绘制技术不同,虚拟内窥镜系统一般可以分为两类:体绘制 (Volume Rendering)和表面绘制(Surface Rendering)。其中体绘制的精度比较 高,缺点是计算量太大,在普通硬件条件下不能达到实时的要求。我们采用表面 绘制的方法构造了一个虚拟支气管内窥镜系统。虽然这种方法精度稍差,但一般 不会影响医生的判断,并且可以在普通微机上实现实时导航。这个系统从流程上 分为几部分:数据获取、支气管分割、表面重建、实时绘制及摄像机控制。 本文的主要工作包括以下几个方面: 1.在分割时,给出了一种自适应门限值的三维扫描线填充区域增长算法, 其分割效果比较好。2.采用Marching Cubes算法对分割好的数掘进行表面重 建。为满足实时绘制的要求,进行了面片简化。3. 在绘制时采用了Gouraud 光照模型及Z-缓冲等技术,并对结果利用RGB-HIS转换进行了伪彩包显示。4.在 导航问题上,给出了一种简化的近似中轴线抽取方法,并将摄像机(即视点)的 位置局限于中轴线上。摄像机模型具有四个自由度:前进及后退、左右转动、上 下转动,以及镜头推移,很好的模拟了摄像机的运动。
Other AbstractWith the development of Medical Imaging techniques together with Virtual Reality and Computer Graphics, computer-aided diagnosis is attracting more and more attention. Hence Virtual Endoscopy techniques were produced. While endoscopy is a normal clinical examination method, Virtual Endoscopy is a good simulation to the real endoscopy based on techniques such as graphics, and on medical imaging techniques. Compared with real endoscopy, VE exainination is less time-consuming, cheaper and not invasive, which can greatly reduce the risk of examination. In some applications it can replace the real endoscopy. Virtual Endoscopy System can be divided into two categories based on the adopted rendering techniques: Volume Rendering and Surface Rendering. Volume rendering method can give a high resolution, but the computing time is very long with ordinary hardware. We constructed a Virtual Bronchus Endoscopy System based on Surface Rendering. The advantage of Surface Rendering is that it can be real-time navigated on a PC. In the meantime, important details are preserved. This system can be divided into the following parts: Data Retrieval, Segmentation of Bronchus, Surface Reconstruction, Real-time Rendering, and Camera Control. The work in this article includes: 1. In segmentation, a 3D Scanline-Filling Region Growing Algorithm based on auto-adapted threshold is presented. The segmentation result is pretty good. 2. The surface of bronchus is reconstructed with Marching Cubes algorithm. Mesh Simplification algorithm is adopted to meet the need of real-time navigation.3. In rendering, techniques such as Gouraud shading model and Z-buffer are adopted, and the results are displayed with pseudo-color by RGB-HSI transform. 4. In navigation, a simplified approximate Median Axis extraction algorithm is presented. The camera (View Point) is restricted on the median axis. The camera has for freedom degree: moving forward and backward, turning upward and downward, turning leftward and rightward, zooming in and out. These four freedom degrees can simulate the movement of camera perfectly.
Other Identifier587
Document Type学位论文
Recommended Citation
GB/T 7714
刘晓峰. 虚拟内窥镜系统的构造和研究[D]. 中国科学院自动化研究所. 中国科学院自动化研究所,2000.
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