【作者】 郁松；

【导师】 樊晓平；

【作者基本信息】 中南大学 ， 交通信息工程及控制， 2011， 博士

【摘要】 随着科技的发展,计算机虚拟技术正在医学领域发挥着重要的作用,其中虚拟手术(又称为手术仿真)越来越多的被医学界所认可,虚拟手术已成为医疗信息学中一个非常重要的应用分支。内窥镜手术复杂程度高,要求临床医生具备较高的手眼协调能力,需要经过长时间的训练。使用虚拟现实技术构建虚拟手术环境,实现内镜手术仿真培训,可以解决传统训练方式下成本高、无法重复等缺陷,目前已成为该领域中的一个非常重要的课题。目前虚拟手术领域已有的研究成果,其重点在于医学图像的分割、三维重建、物理模型的建立,而对于力反馈模型的研究尚处于起步阶段。本文重点研究了三维虚拟现实场景下内窥镜手术仿真中碰撞检测,软组织形变,切割和缝和线打结等关键算法,并对使用这些算法构建内镜手术培训系统进行了探讨。在碰撞检测方面,本文针对内镜手术中碰撞的特点,构造手术器械、软体组织的混合碰撞检测模型,提出了一种基于混合层次包围盒检测算法,根据对算法的分析实验结果,该算法可以改善包围盒对手术器械、软体组织的包围紧密度,提高检测碰撞的速度和确定碰撞点的精度。在提高器官软体组织形变仿真的计算速度上,根据腹腔器官组织的生物力学特征,提出了改进的受力点寻址算法和基于三角面积匹配邻近点查询算法,通过实验证明该算法可以提高形变仿真的响应速度,提高形变计算的实时性,以及仿真精度。在实现软体组织切割仿真方面,针对目前切割仿真算法的缺陷,提出了基于顶点复制的切割分裂算法和基于顶点移动的切割细化算法.通过对比实验验证所提出的算法可以减少网格单元结构的增加,提高切口面的平滑精细程度和切割仿真的响应速度.在实现缝合线打结操作仿真上,结合缝合线的特点,构建了缝合线的3维模型,提出了基于连续控制点的缝合线位置变换算法和基于球体包围盒的碰撞检测算法,实现缝合线打结过程的仿真。更多还原

【Abstract】 With the development of computer technology, the virtual technology is playing an important role in the medical field, the virtual surgery (also known as surgery simulation) has been accepted by the medical field step by step, and the virtual surgery has become a very important branch of the medical informatics.The endoscopic surgery is very complicated, so the clinicians must need a long period of training to gain the capacity of good hand-eye coordination. Using virtual reality technology to build up virtual surgery environment and to implement endoscopic surgery simulation training, can solve the defects of high cost and unable-duplicating in the traditional training mode, which currently has become a very important issue.According to the current research results of virtual surgery, most reseach focuse ong the medical image segmentation, reconstruction, physical model, the study of force-feedback model is in the initial stage.This paper focuses on the key algorithm of collision detection, soft tissue deformation, cutting and suturing-line knotting in the three-dimensional virtual reality simulation of endoscopic surgery, and the construction the training system for endoscopic surgery has been also discussed.In collision detection, according to the characteristics of endoscopic surgery, the mixing collision detection models of surgical instruments and soft tissue were build, a detection algorithm based on mixed-level bounding box was brought up. Based on analysis of experiment results, this algorithm can improved bounding tightness of the bounding box for the surgical instruments and the soft tissue, increase the speed of collision detection and the accuracy of the collision point.To improve the computing speed of the soft tissue deformation simulation, according to the biomechanical characteristics of the abdominal organs, an improved force-point addressing algorithm and the neighboring points query algorithm based on triangle area matching were brought up. According to the experiment result, these algorithms can improve the response speed of deformation simulation, the real-time characteristics and the accuracy of deformation simulation computing.In the realization of soft tissue cutting simulation, to consider the defects in current cutting simulation algorithm, a new cutting-splitting algorithm based on vertex replication and a new cutting-fining algorithm based on vertex moving were proposed. Comparing the experiment results, these algorithms can reduce the increase number of the grid cell after cutting, and improve the cut surface of the smooth sophistication, increase the speed of cutting simulation response.In the realization of suturing-line knotting similation, to conside the characteristics of suturing-line, the 3-D model of suturing-line was build, a transformating algorithm of the suturing-line’s position based on continuous control points and a collision detection algorithm based on sphere bounding were proposed, the simulation of suturing-line’s knotting process was achieved.更多还原