Reseach On The Method Of Three-Dimensional Simulation For Gastric Inner Wall In Virtual Surgery

With the development of virtual reality technology in the field of medical science,virtual surgery system has become a hot topic of scholars.Virtual surgery is mainly to perform a surgical simulation of human soft tissue and organs,soft tissue model as the operation object of virtual surgery system,its performance determines the user's sense of immersion and realism.Therefore,it is very important to establish an effective soft tissue physical deformation model.Stomach as the main organs of the human body,is one of the most likely to disease organs in the clinical,and lesions often appear on the gastric inner wall.For gastric surgery to establish a three-dimensional simulation system of virtual surgery of gastric inner wall that allows doctors to practice repeatedly,and to a certain extent,can improve the success rate of surgery.This paper focuses on the three-dimensional simulation of gastric inner wall,the main research work of this paper includes:(1)To establish the geometric model and biomechanical model of the gastric inner wall.The model of gastric inner wall was obtained by treating gastric model which is reconstructed VHP data set,and the data of gastric inner wall model were stored by ASE file format.Analyzed the biomechanical properties of the gastric inner wall,used elastic mechanics theory to abstract treatment,and established the biomechanical model of the gastric inner wall on the basis of analyzing the viscoelastic model.(2)The establishment of physical deformation model of gastric inner wall.Aiming at the biomechanical properties of the gastric inner wall soft tissue,using mass spring based on viscoelastic to establish the physical deformation model.In order to improve the stability of deformation,presents an improved triangular topology of mass spring model.And then construct the dynamic differential equation of the gastric inner wall,and use the Verlet integral which is improved Euler integral to calculate.Finally,use mouse to control surgical instrument to operate the gastric inner wall,and use the AABB collision and find force point address algorithm to find the force point of gastric inner wall,implement the deformation simulation of gastric inner wall under surgical instrument operation.(3)Adaptive mesh refinement of deformation grid of gastric inner wall.In order to take into account the reality of the simulation of gastric inner wall and real-time problems,at the same time consider that the surgical area of gastric inner wall have larger deformation and need high precision requirements,and non-surgical area have small deformation requires relatively low accuracy,an adaptive mesh refinement algorithm based on softness is proposed.First of all,according to the stress deformation area of gastric inner wall soft tissue to determine the scope of grid subdivision,and then introduce the softness of the mesh as the subdivision criterion to determine the subdivision threshold.In order to make a seamless transition between the subdivision grid and the non-subdivided grid and different degrees of subdivision mesh,formulate rules for crack elimination.Finally,the mesh segmentation is realized in the deformation grid of the gastric inner wall,and the sense of reality of simulation is improved.The low grid model is preserved in the non-operation area,which ensures the computational efficiency.Finally,a 3D simulation system of gastric inner wall based on OpenGL is developed.The algorithm is integrated into the system,and the feasibility of the algorithm is verified by experiments.Experiments show that the algorithm described in this paper can guarantee the real-time performance of the system and improve the simulation realism,which is of great significance to the research of virtual gastric inner wall surgery.