Research On Soft Tissue Cutting And Deformation Simulation For Virtual Laparoscopic Surgery

With the development of science and minimally invasive surgery, vitualsurgery system has been used more and more widely. A virtual minimally invasivelaparoscopic surgery not only trains the doctor in surgery operations, but alsohelps to plan the operation program and other things, and it has popularized thelaparoscopic surgery robot a lot. In this virtual surgery system, scence feedbacksand force feedback are very important ways to make operator and simulationsystem interactive, also the vivid and real-time feedbacks can enhance the realityand immersion of the system. The cutting and deformation simulation of humansoft tissue is an important part of vitual surgery system, so the performances ofreal-time, stability, immertion and reality are required in the operation simulation.Orienting to the virtual minimally invasive laparoscopic surgery, this paperfocuses the research on soft tissue cutting and deformation. Firstly, aftercompareing three main methods in 3D modeling and combining this project'spurposes and demands, this paper has built 3D models of surgery objects andinstruments by manual method, and also kept the 3D model's parameters andrendered data in .3DS and .OBJ. According to the 3D models information thispaper has used C++ and OpenGL to complish the models shown in the simulationby the Microsoft Visual Studio platform.Then, according to the biomechanics characteristics of humun soft tissue thephysical model is built up by using improved spring-mass models, and thecollision detection algorithm in the soft tissue deformation is established,especially a rapid collision detetion is also performed with combination of a roughdetection and accurate detection method. Based on previous work, the simulationof soft tissue deformation has carried out, in which the force feedback informationin real time is calculated based on physical models when surgical instrumentstouching the object. With Omega.7 force feedback device, the operations ofsurgical instruments, output of force feedback information, and force interactionare realized between the user and the simulation platform.For cutting operation of gallbladder surgery, the grid of gallbladder is meshedand the surface mesh model is also established. According to the cutting algorithmof the surface meshinh and combination of rough collision detection algorithm andthe adjacent facet search tree algorithm, the gallbaldder cutting simulation isimplemented with cutting knife operation. This paper also proposes a surface meshcutting algorithm of moving vertex that is suitable for fine meshing, a largenumber of the smallest units, which is only used to cutting operation.Finally, combination of soft tissue deformation simulation and cutting simulation, the virtual cutting and deformation simulation platform is bulit, whichcan realize cystic soft tissue deformation and cutting simulations, while theplatform can achieve different soft tissue deformation simulations with differentsurgrical instruments and soft tissue materials. The simulation results validatesrealtime, accuracy and stability of the developed simulation platform.