Research On Soft Tissue Modeling Technology And Collision Detection Algorithm For Virtual Surgery

Virtual surgery is a typical application of virtual reality technology in medical field,which can help to improve the success rate of surgery and reduce the cost of medical treatment in many aspects such as medical training,surgical planning,intraoperative navigation,etc and is becoming a research hotspot and frontier topic in medical field.The establishment of virtual surgery simulation system involves the intersection and infiltration of many disciplines,which is difficult to study and many functional modules are not perfect.Focusing on the key technology of virtual surgery simulation system,this paper puts emphasis on two core modules of soft tissue modeling method and collision detection algorithm to improve the deformation accuracy of soft tissue model under the condition of satisfying real-time performance of the system.By studying biomechanical properties of soft tissue,and analyzing the viscoelastic properties,the viscoelastic theory is used as the basis of soft tissue modeling.In order to make the model have better visual effect and deformation effect,the geometric model is built by the method of surface model and tetrahedral mesh element complementing each other.The surface model covers the outer surface for visual rendering,and the tetrahedral mesh element is used to support the framework of the physical model,which enhances the fidelity of the model.The physical modeling methods of soft tissue are summarized to pave the way for optimizing the soft tissue model.Aiming at the problem of insufficient viscoelastic performance of soft tissue model,a hybrid soft tissue viscoelastic filling sphere model is proposed by combining three-parameter viscoelastic structure with filling sphere model based on tetrahedral mesh topology.The filling sphere is arranged at the vertex of the tetrahedron mesh,and the spheres are connected by a three-parameter viscoelastic structure to form four sides of the tetrahedron,which shows the "body" characteristics of the model.This method improves the collapse distortion and the deficiency of viscoelastic characteristics of the traditional mass-spring model,improving the deformation accuracy of the model.Based on the improved algorithm,a viscoelastic mixed filling sphere model for liver organs was successfully established,which proved the feasibility of the modeling method.Based on the characteristics of real-time deformation of software,AABB bounding box method is used to construct bounding box tree from top to bottom for virtual objects,which reduces computational complexity and improves real-time performance.Taking the liver organ model and surgical instruments as an example,Axis-aligned bounding boxes method is established to realize collision detection between rigid body and software,which proves the effectiveness of collision detection algorithm.Spring-damping model is used to calculate feedback force for enhancing the reality of virtual surgery.In order to verify the correctness of soft tissue model deformation,a virtual surgical simulation platform is built.The force feedback device is used to exert force on the liver model,which proves that the deformation effect of the model under the force is realistic.The stress-strain simulation experiments show that the model has good relaxation and creep characteristics.