【作者】 王琼；

【导师】 彭延军；

【作者基本信息】 山东科技大学 ， 应用数学， 2008， 硕士

【摘要】 虚拟现实技术是指通过多媒体技术与仿真技术相结合生成逼真的虚拟环境,使用户以自然的方式与环境中的物体进行交互,从而产生身临其境感的一种技术。虚拟手术仿真技术是虚拟现实技术在医学领域的应用,近二十年来这种新型的技术得到了蓬勃发展,这首先得益于虚拟现实在复杂人体三维解剖体数据可视化上的应用,随后发展为可以对人体的可视化结构数据进行实时的操作,运用该技术可以使医务工作者沉浸于虚拟的场景内,学习并体验如何实际的操作各种手术器械,同时学会应付各种临床手术的实际操作。本论文对下颌角的整形手术训练模拟的关键技术进行了研究,重点研究磨骨手术工具与下颌骨模型之间交互的模拟过程,设计并提出了一种基于冲量定理和库仑定律的真实可靠的力反馈模型,开发了同时具备视觉和触觉模拟的虚拟手术训练系统。首先,介绍了使用体数据可视化算法中的面绘制方法,并给出了使用的MarchingCubes方法进行三维重建的头盖骨模型。其中,在骨骼模型三维重建的图像预处理阶段还提出并设计了基于GABOR滤波的MRI图像的边缘检测方法,有效地将头部图像中各部分组织的边缘提取出来,随后根据后续创建力模型的要求,对原始三维模型再进行细分。其次,根据虚拟下颌骨整形手术仿真的需要,针对骨钻与骨骼之间的碰撞问题,提出了基于AABBTree算法的多点碰撞检测模型;基于工具的自转对骨骼产生巨大的冲击力,从而导致骨骼的磨损或去除,论文中结合冲量定理和库仑定律的理论,提出了基于刚体碰撞的力反馈模型来模拟当骨钻与骨骼发生碰撞时骨钻受到的冲击力,体现了骨钻的自转这个重要特征对力模型的影响;在虚拟手术模拟过程中将骨骼和骨钻都视为刚体,提出了适用于刚性物体的骨骼表面变形方法,此方法无需修改表面三角面片的拓扑结构。最后,针对不同的因素对力模型的进行测试,并分析了影响力模型的关键因素和它们之间的关系。更多还原

【Abstract】 Virtual Reality (VR) is a high-end user interface that requires a synthesis generation of the human factors to investigate all aspects of human performance. VR applications strive to simulate real or imaginary scenes with which users can interact and perceive the effects of their action in real time via all five sensorial channels, including visual, auditory, tactile, smell, and taste. Surgery simulator is one of the perfect applications for virtual reality in medicine area. It presents a realistic and feasible approach to train inexperienced surgeons within a safe environment, plays more and more important role in medical field and also changes the world of surgical training. With the help of the virtual surgery simulator, the surgeon can immerse into the realistic environment to learn and experience how to operate so many kinds of surgical instruments in regular situation and how to handle the urgent happenings in advance.This thesis dissertation is mainly devoted to study the main problems of simulating virtual training system for mandibular angle plastic surgery, especially focuses on establishing interaction model between the virtual burr-bone surgical tool and the bone model, designing a hybrid bone surgery training system based on visual and haptic simulation, and proposing a new haptic rendering model based on Impulse Theorem and Coulomb Law.First, we introduce the surface rendering method of volume data visualization and specify how to create the three-dimensional model of the skull with Marching Cubes method. During the pre-processing stage of three three-dimensional reconstruction of the skull model, a new method using 2-D Gabor filters for edge detection and extraction is presented, and experimental results show it is efficient while extracting the edge of MRI medical images. Then, we realize the algorithm to subdivide the original model of the skull in order to create the force feedback model in the next step. Second, according to the requirement of the virtual surgery for mandibular angle plastic surgery, we design the specified surgical tool model and propose the multi-points collision detection model based on AABB Tree data structure. Considering the rotation of the tool having a huge impact force on the bone and making the bone milled and abraded, we decide to reckon the bone and the tool as rigid body in the simulation process of the virtual surgery. With the former analysis, we simulate the collision process between them and propose a haptic rendering model based on Impulse Theorem and Coulomb Law to calculate the force produced because of the contact between the bone and the tool, which gives prominence to the rotation factor of the tool. Then, a simple surface deformation method needs not to change the topology structure is proposed. Finally, we test the force model from many different kinds of sides, and analyze the key factors which affect the force the most, and give the relation chart of them.更多还原