Research On Physical Modeling Method Of Soft Tissue In Virtual Surgery

In recent years,virtual reality technology has been continuously innovated and has been widely applied to the medical field,among which virtual surgery training is the most typical and effective.With the advantages of repeatability,good training effect and low cost,virtual surgical training has broken through the bottleneck of failing to train qualified surgeons in a short time,solved the problem of shortage of surgeon resources effectively,and made a great contribution to the construction and development of human medical and health undertakings.In virtual surgery training,the quality of soft tissue model affects the effect of surgery training directly,so it is very important to establish a real and effective soft tissue model.However,the existing physical models cannot achieve both accuracy and computational efficiency,therefore,this thesis focuses on how to improve the authenticity of the soft tissue deformation simulation and reduce computational complexity,and conducts an in-depth study on the physical modeling method of soft tissue in virtual surgery and improves the corresponding physical modeling method.The main works of this thesis are as follows:(1)To solve the problem that the meshless model is difficult to represent the biomechanical characteristics of soft tissue,this thesis proposes a local high-resolution deformation model of soft tissue based on element-free Galerkin method,this model uses the element-free Galerkin method to simulate the soft tissue deformation,and in which the Kelvin viscoelastic model and adjustment function are applied to simulate the nonlinear viscoelasticity of soft tissues.In addition,a local-high resolution algorithm is applied to sample and render soft tissue deformation regions to provide better visual feedback.(2)To solve the problem of unbalance between accuracy and computational complexity of the meshless model,this thesis proposes a soft tissue deformation model based on Marquardt algorithm and enrichment function.Based on the above nonlinear viscoelastic meshless method,this model uses the Marquardt method to fit the relationship between the force and surface deformation displacement on soft tissue to achieve rapid deformation,and the enrichment function is applied to deal with the discontinuity of soft tissue incision.(3)To solve the problem of difficult parameters selection and unstable structure of the mass-spring model,this thesis proposes an optimized model for the local compression deformation of soft tissue,this model uses the tetrahedron mass-spring model to build soft tissue,and the simulated annealing algorithm is applied to optimize the spring stiffness coefficient and damping coefficient,at the same time,it divides the soft tissue deformation into local deformation region and non-deformation region,the deformation calculation only involves the deformation region.In addition,this model sets a compensation strategy to prevent the model from superelastic effect.By constructing a virtual simulation platform,three models are applied to simulate the deformation of several soft tissues,and the performance of three models are verified by experiments.The simulation and verification results show that the three physical modeling methods of soft tissue that proposed in this thesis improve the authenticity and real-time of soft tissue deformation simulation effectively,and can well implement virtual surgical operations such as soft tissue stretching,compression and cutting,which provides a strong support for virtual surgery training.