Research On Hybrid Modeling And Cutting Of Soft Tissue Based On RPIM-MSM In Virtual Surgery Simulation

The virtual surgery simulation system that combines virtual reality and medicine is a technology that uses computer graphics to reproduce the surgical training scene.It has the advantages of saving the cost of training doctors and avoiding moral and ethical disputes in animal experiments.Pressing and cutting are common operations in the actual surgical process.Therefore,the deformation model and cutting algorithm of soft tissue are the two key technologies of virtual surgery.How to balance the real-time performance and accuracy of the system and how to improve the reality of the simulated incision is the core issue of virtual surgery simulation.This paper studies the soft tissue deformation modeling method and cutting algorithm.Firstly,in order to establish an efficient and accurate soft tissue model,a hybrid soft tissue modeling method based on Radial base Point Interpolation Method(RPIM)and Mass Spring Method(MSM)is proposed.The model is divided into surgical(lesion)area and non-surgical(health)area according to functional areas to balance the realtime and accuracy of the system.The RPIM in the operating area introduces the implicit integration method to ensure the stability and high precision of the operating area of the system.The non-operating area adopts the MSM model with a small calculation amount to reduce the computational complexity.At the same time,the proposed biomechanics-based mass spring method can effectively express the nonlinearity and viscoelasticity of healthy biological tissues.Under the premise of ensuring accuracy,the hybrid modeling method of dividing functional areas improves computational efficiency.In order to alleviate the fragmentation of the model functional area,an edge extraction strategy based on the support domain is proposed to establish the transition area.The experimental results verify the effectiveness of the modeling method.Secondly,in order to solve the problems of distorted mesh and non-smooth cut shape when cutting the mesh-based model,this paper proposes a new cutting algorithm to be applied to simulate soft tissue cutting based on the RPIM-MSM hybrid model.In order to alleviate the unevenness of the cut edge,a cut reproduction method based on the extended Bezier curve is proposed.The extended Bezier curve joins the traditional Bezier curve to solve the problem that the curve cannot pass through the contact point.In addition,the adaptive strategy has further improved the visual feedback effect.The cutting algorithm is applied to the virtual surgery simulation system and compared with real incision,and the experimental results have achieved better visual effects.Finally,in order to verify the practicability of the proposed modeling method and cutting algorithm,a virtual surgery simulation system based on laparoscopic liver surgery was built.Deformation and cutting tests were carried out in the virtual liver surgery simulation system,and the calculation time of the system was recorded.The results show that the system has high fidelity and meets the real-time requirements of virtual surgery.