Soft Tissue Deformation Simulation Based On Nonlinear Biomechanical Model And Meshless Galerkin Method

Virtual surgery is a virtual reality application especially designed for simulate varieties of phenomenon during the simulation of surgery, which combine to external interactive devices can provide a realistic surgery scene for doctors, and ultimately achieve the purposes of reduce surgical training costs, improve surgical treatment, reduce the patient’s pain during surgery and reduce the risk of surgery. Currently, the soft tissue deformation calculation is based on the finite element method in most of virtual surgery system, but the accuracy and stability of calculation method based on mesh will be sharp decline when the calculation method influenced by distortion mesh such large deformation and cutting operations, which seriously affecting the deformation simulation process. This paper focus on the shortcomings of current deformation model, established the deformation model of soft tissue based on meshless method and theory of viscoelastic mechanics, finally realize the simulation of soft tissue deformation.This paper used the meshless method to calculate the soft tissue deformation for the problem of low accuracy and poor stability of finite element method. Meshless method is high accuracy and stability, especially suit for large deformation, which can great improve simulation accuracy and stability under large deformation. This paper established nonlinear viscoelastic model based on meshless method according to biomechanical properties and viscoelastic theory in soft tissue deformation modeling. Firstly studied classical linear elastic model and get the general structural linear viscoelastic model by linear elastic model, establish the nonlinear viscoelastic biomechanical model of soft tissue by adding nonlinear adjust function into the general structure of linear elastic model. The meshless nonlinear viscoelastic deformation model of soft tissue was built up through combine the nonlinear viscoelastic model with meshless method and derived the total system control equations. The model in this paper can show viscoelastic of soft tissue according the relationship between stress-strain and time, which also can show the nonlinear property by controlling the parameters of nonlinear adjust function, the mechanical properties of soft tissue deformation process can be calculated through the total system control equations and finally simulated the deformation process of soft tissue.The two-dimensional cantilever beam model was used to verify the validity of meshless method at first, and then the liver model was selected as the deformation model to verify the validity of model proposed in this paper. The experiment shows that the meshless method nonlinear viscoelastic model can real reflected the deformation process as well as the mechanical properties. Because the meshless method was used during the calculation process, which not only ensure the accuracy and stability of deformation, but also avoid the problem of mesh distortion and reconstruction in the finite method.