Research On Key Techniques Of Soft Tissue Deformation Modeling And Suture Simulation In Virtual Surgery

As a typical application of virtual reality technology in clinical medicine,virtual surgery can establish a surgical training scene integrating visual,tactile and auditory senses,and bring users immersive interactive experience,which is of great value for changing the traditional medical training mode and improving the professional level of medical staff.Suture is one of the most training operations for surgeons and also the key and difficult points in virtual surgery.However,the existing virtual surgical suture simulation system is difficult to accurately show the structural characteristics of the suture line such as bending and torsion,and it is difficult to obtain realistic suture interaction effects,such as the effect of suture deformation between the suture line and soft tissue.In order to solve the above problems,we built a virtual surgical suture simulation system suitable for simple suture of liver trauma,and carried out research on two key techniques of suture modeling and soft tissue deformation modeling.The main contributions of this paper are as follows:Firstly,a suture model based on Kirchhoff elastic rod theory is proposed.Suture is the most important surgical instrument in suture operation.Traditional geometric modeling method can’t provide real feedback force,and it is difficult to accurately show the structural characteristics of suture,such as bending and torsion.Different from the traditional methods,the proposed method fully considers the calculation of the tensile,torsional and flexural elasticity of the suture,and uses the improved Euler method to solve the equation of motion,thus realizing the simulation of various dynamic behaviors of virtual surgical suture.In order to avoid collision misdetection and missing detection effectively,a vector-based self-collision detection method was proposed,and repulsive force calculation was added to suture lines,which could achieve realistic force feedback effect.In addition,we introduce adaptive discretization strategy to realize efficient knotting simulation operation.The experimental results show that compared with the model constructed by particle spring,the proposed model is more realistic and can complete complex knotting simulation.Secondly,a particle spring model based on biological characteristics is proposed.In the process of suture interaction,sutures will lead to complex deformation of soft tissue model.Realistic soft tissue modeling can significantly improve the authenticity of virtual surgical system.The traditional mass spring model can only show a single soft tissue viscoelasticity.Different from the traditional particle spring model,the particle spring model based on biological characteristics is composed of virtual spring,damping spring and nonlinear spring.Virtual spring and damping spring can better simulate the quasi-incompressibility and viscoelasticity of real soft tissue,and nonlinear spring can realize the nonlinearity of soft tissue.In addition,based on local body mesh modeling,the model is divided into wound region and non-wound region according to function,which further improves the computational efficiency.In order to ensure the correct interaction of sutures within soft tissue,position constraint was introduced into the traditional sliding constraint point method,and suture control method was adopted to supervise the interaction process,so as to avoid problems such as failure of sutures to slide and secondary wound cracking.The experimental results show that the proposed model can effectively simulate various biomechanical properties of soft tissue and achieve a realistic suture interaction effect.Finally,a virtual surgical suture simulation system was established for simple suture of liver trauma.The system includes visual rendering module,interactive computing module and force feedback module,which can truly reproduce surgical knotting and suture operations.The experimental results show that the system has high real-time performance,and the model and method proposed in this paper can meet the actual needs of virtual surgical system.