基于四面体网格的软组织位置动力学切割仿真算法

Algorithm of position-based dynamics and cutting simulation for soft tissue using tetrahedral mesh

为满足虚拟手术中软组织变形与手术模拟的真实性和实时性要求,提出了一种基于四面体网格和位置动力学的软组织切割模拟算法.首先,本算法以四面体作为软组织几何模型的基本操作单元,物理模型采用位置动力学模型驱动软组织变形,四面体网格的凸包形成软组织的外表面.其次,本算法对位置动力学模型进行了扩展,支持了模型拓扑改变的情况,使其适用于软组织的切割模拟.再次,利用支持纹理信息的四面体网格作为几何模型,能生成细节丰富的切口.最后,在该算法上实现了力反馈设备的应用,增加了切割过程中的触觉模拟,增强了虚拟手术中手术环境和过程模拟的真实性.实验表明:该模型能提供真实和高效的变形模拟,并具有较高稳定性和可操作性.本算法目前已应用在北航虚拟现实技术与系统国家重点实验室开发的医学手术模拟器上.合作医院在使用模拟器进行的腹腔镜检查手术方面已经做了前导性的研究,医生对模拟器评价也较高.

In order to improve the realism and real-time performance of virtual surgery technique, a cutting algorithm for soft tissue using tetrahedral mesh and position-based dynamics was proposed. Firstly, the tetrahedral mesh was chosen as the geometrical model for soft tissue, and position-based dynamics were employed as the physical model. The external surface of soft tissue was formed by the convex hull of the tetrahedral mesh. Secondly, to support the cutting simulation, we also modified the position-based dynamics method to ensure it worked well when the topology of soft tissue model changed. Moreover, the tetrahedral mesh cou- pled with texture information was applied for the highly-detailed incision exposure. Finally, the haptic rendering was implemented on this dissection algorithm to enhance the realism of the surgery simulation environment. The experimental result shows that the simulator works effectively and stably with this physical model, when deformation and dissection occurs. Moreover, the algorithm has been used in the virtual surgery simulator designed by State Key Laboratory of Virtual Reality Technology and Systems in Beihang University. The laparoscopic surgeons from cooperative hospitals have given a pilot study and high evaluation has been given from the doctors for this simulator.