Research On Methods Of Cutting Tetrahedron In Virtual Surgery Simulation

Medicine is becoming one of the major application fields for Virtual Reality (VR), due to rapid development of Scientific Visualization in recent years. Surgery Simulation System is a medical Virtual Reality system dedicated to simulating the dynamic process in surgery. It involves the visualization of medical data (usually anatomical), interaction with the visualized data, simulating behaviors of body deformation and feedback in modalities of vision, sound, force, touch, and smell. VR with a medical application combines research in Computer Graphics, Computer Vision, Biomechanics, Robotics and Medicine.Cutting process of soft tissue and organs is very important in virtual surgery simulation. Tetrahedron is widely used to construct the geometric model of virtual organs. Efficient methods must be developed to split or merge tetrahedrons in order to adapt to topology changes during cutting process. The main parts of this thesis are the two chapters on "Reconstruction of Tetrahedrons" and "Stability of Tetrahedrons" .Main research work I have done is listed as follows:1) Reconstruction of Tetrahedrons.Noticing the difference in constructing partially cut tetrahedron and fully cut tetrahedron, we take two different approaches to reconstruct tetrahedron. The crack free method is used for partially cut tetrahedron and minimal set method is used for fully cut tetrahedron. This is a reasonable compromise between reducing the number of tetrahedrons generated and complexity of reconstruction.2) Stability of Tetrahedrons.The quality and quantity of the newly generated tetrahedrons will greatly affect the subsequent computations. The stability of the model depends on each individual tetrahedron. A single unstable tetrahedron could lead to instability of the entire model. Two ways to measure stability of tetrahedrons will be introduced. An earlier method to improve tetrahedron stability, the Snap Method, will be briefly discussed. Then techniques used in Delaunay. triangulation to deal with degenerated elements will bethoroughly investigated. These techniques, element deletion and face swapping, will be used for improving stability of tetrahedrons in this thesis.