基于CT的虚拟内窥镜系统
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摘要
虚拟内窥镜技术(Virtual Endoscopy)是目前的一个研究热点问题,是一个多学科交叉的研究领域,是虚拟现实技术在现代医学中的应用,它涉及图像处理、计算机图形学、科学计算可视化、虚拟现实技术以及医学领域的相关知识。虚拟内窥镜技术克服了传统光学内窥镜需把内窥镜体插入人体内的缺点,是一种完全无接触式的检查方法。虚拟内窥镜的研究旨在为医生提供诊断依据,还可应用于手术规划、实现手术的精确定位和医务人员的培训等。
本文综述了虚拟内窥镜系统的结构和技术组成,针对虚拟内窥镜系统的若干关键技术,进行了深入研究和探讨。虚拟内窥镜系统的研究内容主要包括医学图像的处理,如插值、滤波等;组织和器官的分割与提取;组织和器官的三维绘制技术;虚拟内窥镜系统的路径规划;虚拟内窥镜系统的实时绘制等。
Marching Cubes(MC)算法是基于规则体数据抽取等值面的经典算法。本文详细叙述了MC算法的过程,并针对MC算法进行了详细的分析和改进,为了提高计算效率,提出了一种基于MC和区域增长抽取等值面方法,以及确定法向量的新方法。
在路径规划方面,基于距离变换的基础上,设计了一种新的快速、高效的抽取中心路径的算法,并提出了相应的路径平滑技术。根据起点和终点,确定空腔组织的中心路径点,在两维切平面中计算体素到表面的距离,将局部最大值(距对象表面的距离大于邻近体素的距离)作为中心路径上的体素点,而不是在三维空间中计算,使计算量大为减少。
在虚拟内窥漫游方面,给出了虚拟摄像机模型的定义,并对虚拟摄像机的几何定位和行为模拟进行了描述。
针对今后的研究工作,结合我们系统开发设计中的体会和不足,对以后的研究中需要进一步深入研究的几个方面做了一个简单的展望。
Virtual Endoscopy is a very hot object in recent research. It is an application of virtual reality in modern medicine. As a multidisciplinary research field ,it incorporates the knowledge about Computer Graphics, Image Processing, Scientific Computing Visualization , Virtual Reality, and something in medicine . It is a non-touched medical diagnoses method since it avoids the risk of invading body when the actual optical endoscopy is used. The aim of Virtual Endoscopy system research is to provide trusty means for medical diagnoses, and to spread the application to precision orientation of surgery , personnel planning and training ,etc.The structure and modules arc surveyed in this thesis . Some key techniques existing in virtual endoscopy system are also studied . The research about VE consists of Image pretreatment (eg. interpolation and filter) , segment and abstraction of tissues , 3D construction , path planning , and real-time rendering.Marching Cubes is a classical algorithm about isosurface abstraction from regulated volume data. The process of MC is discussed in detail . A more efficient algorithm based on MC and region growing is proposed. And the new method of calculate the normal is also given.In path planning , a faster and a more efficient algorithm based on distance transform is designed . The center point of the hollow tissue is decided by the start point and end point . The distance from inner voxels to boundary surface was computed in section plane. The voxel point with local maximum distance value ( the distance value of a point in section plane is larger than its neighbor voxels' distance value) was taken as the center point. The computation is reduced since it is not executed in 3D space.In VE fly through , the model of virtual camera is defined and its geometric loccation and behavior is described.
Future researches are pointed out considering the shortcomings and experiences of our system and the development trend.
本文综述了虚拟内窥镜系统的结构和技术组成,针对虚拟内窥镜系统的若干关键技术,进行了深入研究和探讨。虚拟内窥镜系统的研究内容主要包括医学图像的处理,如插值、滤波等;组织和器官的分割与提取;组织和器官的三维绘制技术;虚拟内窥镜系统的路径规划;虚拟内窥镜系统的实时绘制等。
Marching Cubes(MC)算法是基于规则体数据抽取等值面的经典算法。本文详细叙述了MC算法的过程,并针对MC算法进行了详细的分析和改进,为了提高计算效率,提出了一种基于MC和区域增长抽取等值面方法,以及确定法向量的新方法。
在路径规划方面,基于距离变换的基础上,设计了一种新的快速、高效的抽取中心路径的算法,并提出了相应的路径平滑技术。根据起点和终点,确定空腔组织的中心路径点,在两维切平面中计算体素到表面的距离,将局部最大值(距对象表面的距离大于邻近体素的距离)作为中心路径上的体素点,而不是在三维空间中计算,使计算量大为减少。
在虚拟内窥漫游方面,给出了虚拟摄像机模型的定义,并对虚拟摄像机的几何定位和行为模拟进行了描述。
针对今后的研究工作,结合我们系统开发设计中的体会和不足,对以后的研究中需要进一步深入研究的几个方面做了一个简单的展望。
Virtual Endoscopy is a very hot object in recent research. It is an application of virtual reality in modern medicine. As a multidisciplinary research field ,it incorporates the knowledge about Computer Graphics, Image Processing, Scientific Computing Visualization , Virtual Reality, and something in medicine . It is a non-touched medical diagnoses method since it avoids the risk of invading body when the actual optical endoscopy is used. The aim of Virtual Endoscopy system research is to provide trusty means for medical diagnoses, and to spread the application to precision orientation of surgery , personnel planning and training ,etc.The structure and modules arc surveyed in this thesis . Some key techniques existing in virtual endoscopy system are also studied . The research about VE consists of Image pretreatment (eg. interpolation and filter) , segment and abstraction of tissues , 3D construction , path planning , and real-time rendering.Marching Cubes is a classical algorithm about isosurface abstraction from regulated volume data. The process of MC is discussed in detail . A more efficient algorithm based on MC and region growing is proposed. And the new method of calculate the normal is also given.In path planning , a faster and a more efficient algorithm based on distance transform is designed . The center point of the hollow tissue is decided by the start point and end point . The distance from inner voxels to boundary surface was computed in section plane. The voxel point with local maximum distance value ( the distance value of a point in section plane is larger than its neighbor voxels' distance value) was taken as the center point. The computation is reduced since it is not executed in 3D space.In VE fly through , the model of virtual camera is defined and its geometric loccation and behavior is described.
Future researches are pointed out considering the shortcomings and experiences of our system and the development trend.
引文
[1] Vining D, Gelfand D, Bechtold R et al. Technical Feasibility of Colon Imaging with Helical CT and Virtual Reality[A].Annual Meeting of American Roentgen Ray Society[C],New Orleans LA. 1994, pp. 104.
[2] T Nakasatoa, M Sasakia, S Ehara, et al. Virtual CT endoscopy of ossicles in the middle ear. Journal of Clinical Imaging. 2001,25(3):171-177
[3] D Buthiau, E Antoine, J C Piette, et al. Virtual tracheo-bronchial endoscopy: educational and diagnostic value. Surg Radiol Anat, 1999,18(2):125-131
[4] G C Kagadis, V Patrinou, C P Kaloger, et al. Virtual endoscopy in the diagnosis of an adult double tracheal brobchi case. European Journal of Radiology, 2001,40(9):50-53
[5] D Bartza, O Grvitb, M Lanzendo, et al. Virtual Endoscopy for Cardio Vascular Exploration. In Computer Aided Radiology and Surgery(CARS 2001),Berlin, 2001, 1005-1009
[6] A Radetzky, A Nu. Visualization and Simulation Technigues for Surgical simulators Using Actual Patient's Data. Artificial Intelligence in Medicine 2002,26(4):255-279
[7] 罗希平,田捷,诸葛婴等.图像分割方法综述.模式识别与人工智能.1999,PP:300-312。
[8] A.X. Falcao, J. K. Udupa et al .User-steered image segmentation paradigms:Livewire and livelane. Graphical Models and Image Processing, 1998, 60:233-260
[9] W E Lorensen, H E Cline. Marching cube, a high resolution 3D surface reconstruction algorithm[J].Computer Graphics, 1987, 21 (4): 163-169.
[10] 管伟光.体视化技术及其应用.第一版,北京,电子工业出版社.1998.
[11] Nielson G.,Hamann B..The Asymptotic Decider:Resolving the Ambiguity in Marching Cube. Visualization' 91,1991:83-91
[12] J. Wilhelms and A. Van Gelder. Topological considerations in isosurface generation. San Diego Workshop on Volume Visualization, 1990
[13] Shu, R.,Chen, Z.,Kankanhali, M.S..Adaptive marching cubes, The Visual Computer, 1995,11:202-217
[14] 梁友栋.多边形平均法向量的新定义和计算[J] 中国科学E,2000,30(5):448-452.
[15] YANG Xing-Qiiang, ZHANG Cai-Ming. A Modified Cuberille Method with LinearPrecision. Journal of Computer Reserch and Devlopment, 2004, 41(7): 1213-1219.
[16] 缪斌和,邓元木,黄斐增等.基于对应点匹配断层图像三维插值方法.中国医学物理学杂志.17(1),2000:14-16.
[17] Vilanova A, Konig A, Groller E. VirEn:A Virtual Endoscopy System[d] Machine Graphics & Vision, 1999,8(3):469-487
[18] Astheimer, P., Poche, M..Level-of-Detail generation and its application in virtual reality. In: Singh, G., Feiner, S.K., Thalmann, D., eds. Virtual Reality Software and Technology: Proceedings of the VRST' 94 Conference. World Scientific, 1994, 299-309.
[19] C. Ma, M. Sonka. A Fully Parallel 3D Thining Algorithm and TtsApplications. Computer Vision and Image Understanding, vol.64, no. 3, 1996, pp420-433.
[20] K Palagyi, A. Kuba. A 3-subiteration 3D thinning algorithm for extracting medical surface. Pattern Recognition Letters, 2002,23(6): 663-675,
[21] T S He, L Hong. Reliable navigation for virtual endoscopy. Nuclear Science symposium. IEEE. Washington: IEEE Press, 2000,1339-1343
[22] G Boregefores. Distance transformation on digital images. Computer Vision Graphics Image Processing, IEEE. Heidelberg: IEEE Press, 1986, 344-371
[23] S Ali, S I Hamid, A I Reza. Fast skeletonization algorithm for 3D elongated objects .SPIE, Image Processing 2001(4322).San Diego:SPIE Press , 2001,323-330
[24] T S He, L Hong, D Q Chen. Reliable path for virtual endoscopy: Ensuring complete examination of human organs. IEEE Trans. on Visualization and Computer Graphics, 2001, 7(4):333-342
[25] Zhang, M.J.,Hu, X.F.,and Ku, X.S. "PanVideo: An Efficent Approach for Motion Modeling and Motion Estimation of the Camera" .Journal of Image and Graphics of China, 1997
[26] 申皓、唐泽圣。分支结构中的虚拟内窥镜技术[J].系统仿真报,2004.11.20-23
[2] T Nakasatoa, M Sasakia, S Ehara, et al. Virtual CT endoscopy of ossicles in the middle ear. Journal of Clinical Imaging. 2001,25(3):171-177
[3] D Buthiau, E Antoine, J C Piette, et al. Virtual tracheo-bronchial endoscopy: educational and diagnostic value. Surg Radiol Anat, 1999,18(2):125-131
[4] G C Kagadis, V Patrinou, C P Kaloger, et al. Virtual endoscopy in the diagnosis of an adult double tracheal brobchi case. European Journal of Radiology, 2001,40(9):50-53
[5] D Bartza, O Grvitb, M Lanzendo, et al. Virtual Endoscopy for Cardio Vascular Exploration. In Computer Aided Radiology and Surgery(CARS 2001),Berlin, 2001, 1005-1009
[6] A Radetzky, A Nu. Visualization and Simulation Technigues for Surgical simulators Using Actual Patient's Data. Artificial Intelligence in Medicine 2002,26(4):255-279
[7] 罗希平,田捷,诸葛婴等.图像分割方法综述.模式识别与人工智能.1999,PP:300-312。
[8] A.X. Falcao, J. K. Udupa et al .User-steered image segmentation paradigms:Livewire and livelane. Graphical Models and Image Processing, 1998, 60:233-260
[9] W E Lorensen, H E Cline. Marching cube, a high resolution 3D surface reconstruction algorithm[J].Computer Graphics, 1987, 21 (4): 163-169.
[10] 管伟光.体视化技术及其应用.第一版,北京,电子工业出版社.1998.
[11] Nielson G.,Hamann B..The Asymptotic Decider:Resolving the Ambiguity in Marching Cube. Visualization' 91,1991:83-91
[12] J. Wilhelms and A. Van Gelder. Topological considerations in isosurface generation. San Diego Workshop on Volume Visualization, 1990
[13] Shu, R.,Chen, Z.,Kankanhali, M.S..Adaptive marching cubes, The Visual Computer, 1995,11:202-217
[14] 梁友栋.多边形平均法向量的新定义和计算[J] 中国科学E,2000,30(5):448-452.
[15] YANG Xing-Qiiang, ZHANG Cai-Ming. A Modified Cuberille Method with LinearPrecision. Journal of Computer Reserch and Devlopment, 2004, 41(7): 1213-1219.
[16] 缪斌和,邓元木,黄斐增等.基于对应点匹配断层图像三维插值方法.中国医学物理学杂志.17(1),2000:14-16.
[17] Vilanova A, Konig A, Groller E. VirEn:A Virtual Endoscopy System[d] Machine Graphics & Vision, 1999,8(3):469-487
[18] Astheimer, P., Poche, M..Level-of-Detail generation and its application in virtual reality. In: Singh, G., Feiner, S.K., Thalmann, D., eds. Virtual Reality Software and Technology: Proceedings of the VRST' 94 Conference. World Scientific, 1994, 299-309.
[19] C. Ma, M. Sonka. A Fully Parallel 3D Thining Algorithm and TtsApplications. Computer Vision and Image Understanding, vol.64, no. 3, 1996, pp420-433.
[20] K Palagyi, A. Kuba. A 3-subiteration 3D thinning algorithm for extracting medical surface. Pattern Recognition Letters, 2002,23(6): 663-675,
[21] T S He, L Hong. Reliable navigation for virtual endoscopy. Nuclear Science symposium. IEEE. Washington: IEEE Press, 2000,1339-1343
[22] G Boregefores. Distance transformation on digital images. Computer Vision Graphics Image Processing, IEEE. Heidelberg: IEEE Press, 1986, 344-371
[23] S Ali, S I Hamid, A I Reza. Fast skeletonization algorithm for 3D elongated objects .SPIE, Image Processing 2001(4322).San Diego:SPIE Press , 2001,323-330
[24] T S He, L Hong, D Q Chen. Reliable path for virtual endoscopy: Ensuring complete examination of human organs. IEEE Trans. on Visualization and Computer Graphics, 2001, 7(4):333-342
[25] Zhang, M.J.,Hu, X.F.,and Ku, X.S. "PanVideo: An Efficent Approach for Motion Modeling and Motion Estimation of the Camera" .Journal of Image and Graphics of China, 1997
[26] 申皓、唐泽圣。分支结构中的虚拟内窥镜技术[J].系统仿真报,2004.11.20-23