The Research On Cutting And Reconstructing The Model Of Soft-tissue In Virtual Surgery

With the development of modern science technology, computer technology has beenwidely used in different kinds of fields. It brings a great change for human’s study,entertainment, works and so on. At the same time, computer science is looking for a fast,effective, safe and economical method to train surgeon in medical field. As a result, virtualsurgery system appears.By using human-machine interface and force-feedback equipment, users can takesurgery practice, get surgery education and plan surgery in virtual surgery system.Designing the software of virtual surgery system includes geometrical modeling, physicalmodeling, collision test, shape calculation and cutting simulation.This paper constructs a surface mesh model of soft-tissue and a basic physical modelbased on the mass-spring method. It takes AABB (Axis-aligned bounding box) boundingvolume as the method of collision detection technique. The calculation of shaping takesadvantage of the static spreading method.The most important part is the research on cutting simulation in this paper. There aretwo main aspects as following:(1) It uses two methods to deal with reconstructing triangle cells of the geometricalmodel. One method is based on the convex polygon constructing. It is described that itabandons reconstructing each cell individually. But it forms convex polygons by takingadvantage of the relationship of current cell and its neighbors. The other method is basedon the original method of moving vertexes and copying intersection vertexes. It takes theequal dividing points of the cutting line as the target points, and moves vertexes needed tothem. It really avoids creating bad cells.(2) This paper analyses the orginal method of groove constructing. As the differentproportion between cutting edges and its depth leads to different qualities of created cells,it reconstructs the cells of groove based on the method of Bezier Curve. The qualities oftriangle cells reconstrcted are improved a lot by repeated taking advantage of techniquebased on Bezier Curve.It is proved in the theory and experiment that the method mentioned above increases the quality of cells. It is better for second cutting simulation.