Soft Tissue Modeling Based An Medical Images And Its Application In Virtual Surgery

The virtual surgery simulation system establishes the model of surgical instruments and tissues on the computer,and simulates the interactive scenes between surgical instruments and tissues,which is used for surgical training and guidance,surgical plan formulation and optimization,surgical navigation and so on.In virtual surgery simulation systems,the interaction of surgical instruments with soft tissue is difficult.It is first necessary to establish an accurate geometric model of the tissue organ.Secondly,various types of surgical operations such as soft tissue touch,lifting,cutting,suturing,and aspiration are based on soft tissue deformation.The core of the virtual surgery simulation system of soft tissue is the deformation model.Constructing an accurate and real-time soft tissue deformation model has always been the focus and difficulty of virtual surgery simulation system research.Therefore,in order to improve the authenticity and real-time of visual and tactile feedback of the system,and to let users experience the lifelike deformation process as real surgery,a kidney virtual surgery simulation system is developed.Firstly,the improved marching cubes algorithm based on medical images constructs a geometric model of the kidney.For the problems of the classical marching cubes algorithm,such as too much computation,complex topology,long rendering time and the accuracy of the three-dimensional model is relatively low.In this paper,an adaptive improved marching cubes algorithm based on the general tree structure of region growing method and the moving equivalence point method is proposed.The algorithm performs medical image segmentation,then selects the seed points and marks all the volume elements intersecting with the threshold.The general tree structure is created,and the intersecting volume element is inserted into the child nodes to determine the vertex index method based on the general tree.By moving the equivalence point to merge the coplanar triangle,the information of the equivalence point is simplified and the algebraic operation is reduced.The modeling of surgical instruments is modeled by proxy point method.The experimental results show that compared with the traditional moving cube algorithm,the improved algorithm has better precision of rendering model and higher efficiency of algorithm execution.Secondly,the physically-based deformation model of kidney is based on the improved spring mass model.Aiming at the problem that the parameters of the classical spring particle model are fixed and the deformation process is relatively not true and accurate,the proposed improved spring particle model can more realistically represent the deformation process of the kidney.Through the surgical puncture experiment on the kidney of animals,the dynamic changes of soft tissue deformation were analyzed.By sampling and fitting experimental data,various parameters in the improved spring mass model were determined,and the more realistic dynamic change law of the spring was obtained by the particle model.Through the deformation effect of the virtual model of the kidney and the computational efficiency of the system,the improved spring mass model can achieve real and accurate deformation,satisfying the authenticity and realtime requirements of the system.Finally,this paper completed the virtual surgery simulation system of the kidney,which can realize the operation of the renal pressure.The kidney virtual surgery simulation system developed in this paper is divided into initialization,visual thread and tactile thread.The system first performs an environment initialization,recycling the execution of visual threads and haptic threads.By displaying the platform of virtual surgery system and experimental results,it shows that the system can truly reproduce the operation process of kidney,and has high fluency and accuracy of operation.The kidney virtual surgery system developed in this paper has good authenticity and realtime performance.