Research Of Deformation Model Of Soft Tissue In Neurosurgical Simulation For Brain Tumor Dissection

How to train young neurosurgeons safely and efficiently is a long-standing problem.With development of computer technology,surgical simulation based on virtual reality enables young neurosurgeons to gain hands-on experience in a risk-free environment.However,the research of neurosurgical simulation is still in its infancy because of the complexity of the micro-neurosurgery.In this work,a series of theoretical studies and simulation experiments are carried out,answering the problems and challenges that the soft tissue deformation model still faces in the virtual brain tumor surgery.This work improves the performance of soft tissue deformation model in aspects of accuracy,real-time performance,and interactivity.A high degree of computional accuracy and efficiency is achieved,making it suitable for the simulation of deformation of soft tissue in interactive and rupture situation.The theoretical results are incorporated into development of a neurosurgical simulation system.The results of this paper are summarized as follows:1.The existing soft tissue deformation model can not meet the real-time and accuracy requirement of surgical simulation at the same time.To address this question,a new Finit Element Method(FEM)brain tissue deformation model,which is based on the optimization implicit Euler method,is proposed.Both the anisotropic and viscoelastic properites of brain tissue are incorporated into the model,which provides more accurate and realistic imitation of the deformation of brain tissue.A descent method with GPU-based implementation is used to solve the optimization problem,which makes it possible to achieve a high degree of computational efficiency.Simulation results show that both the anisotropic and viscoelastic behaviors are presented in the deformation model.The GPU-based implementation of the proposed model improves significantly the computational efficiency over CPU-based FEM models with the implicit integration scheme.2.Based on the proposed deformation model,a new energy function of constraints characterizing the interaction between the virtual instrument and the soft tissue is incorporated.Distance and permanent deformation constraints are introduced to describe the interaction in the convexity meningioma dissection and hemostasis.Simulation results show that the soft tissue model exhibits the behaviors of adhesion and permanent deformation under the constraints.A high degree of computational accuracy and efficiency can be achieved.The proposed model was implemented in the development of a neurosurgical simulator,in which surgical procedures such as dissection of convexity meningioma and hemostasis were simulated.3.A new model of connective tissue damage for blunt dissection of brain tumor is proposed.The damage starts and develops in the connective tissue with an evolution criterion as the external load is applied.The rupture occurs in the connective tissue as the damage accumulates to the threshold value.Specifically,the tool-tissue interaction is incorporated into the model of connective tissue damage.Moreover,a reconstruct algorithm of surface mesh of brain tissue model is introduced.Analysis and experiments show that the model of soft tissue damage provides stable,visually realistic results for the simulation of rupture process of connective tissue.The proposed model of connective tissue damage was incorporated into the development of a neurosurgery simulator,in which the blunt dissection of brain tumor was simulated.4.A neurosurgery simulation system was implemented based the prosed model.Simulation of blunt dissection of a brain tumor is achieved.Technical difficulties in 3d reconstruction,collision detection,visual rendering are solved.A framework of surgical simulation system is developed.