Study Of Soft Tissue Cutting And Deformation Simulation In Virtual Surgery

A virtual surgery simulation system is mainly used in medical education, surgical planning, surgical training, ancillary support in surgery, and the cutting deformation simulation of body's soft tissues and organs is an important part of a virtual surgery simulation which needs to meet the real-time, stability and realistic demands. For the deformation model, the general mass-spring model can meet the requirement of real-time, but it does not have the stability. Although the traditional finite element model can be the more accurate simulation of visco-elastic characteristics, but the huge time consumption makes this method difficult to give real-time feedback. For cutting models, Although the cutting based on removing the elements can be easily implemented, but the simulation effect may has distortion and loss of material, and the cutting based on separating faces is only suitable for the surfaces cutting but not suitable for solids, Although the cutting based on separating volume elements is more realistic, but it will increase the number of the geometric elements, resulting in the reduction of computational efficiency or even the failure of numerical calculation.In this paper, we propose the tetrahedral shape matching deformation model, and in order to make the deformation results more realistic we propose to use the relationship of connected points to achieve the shape matching area to improve deformation degree of freedom and the details of the display. In the cutting model, this paper selects and implements a cutting algorithm that finding the approximate faces of the cutting surface to achieve the cutting, this algorithm maintains the mesh size and its cutting effect is realistic. In the process of integration processes, in order to facilitate the follow-up rendering and real reflect the cutting effect, this paper proposes a regular and extensible geometric modeling method, that is, the method of generating the tetrahedral mesh from equidistant sampling points, using the randomized incremental flip algorithm to achieve it. The above-mentioned three areas of our work make a fast, stable and realistic cutting deformation simulation be achieved.This cutting deformation algorithm satisfies the real-time, stability and realistic effect. Deformation based on shape matching algorithm has the speed of the mass spring system and has the stability that the mass spring system does not have. Further more, by using the relationship of connected points to achieve the shape matching area, our model can achieve the realistic effect that can be comparable to the effect finite element method has. And the cutting algorithm that finding the approximate faces of the cutting surface makes the cut smooth. This cutting algorithm has an increase of authenticity at the same time without increasing the number of elements in the mesh, so it has not the shortcomings produced by the cutting algorithm based on element division which has additional elements must be calculated. This geometric modeling method generating the tetrahedral mesh from the equidistant sampling points is a regular and extensible method. We can reuse the geometric model and the cutting algorithm but only replace deformable model if we want. Further more, the generated mesh is regular and it has not the worry that the mesh directly generated by surface model has worse aspect ratio. All of the above-mentioned advantages make the cutting deformation simulation of this paper be stable, real-time and realistic.