Human Soft Tissue Deformation Simulation In Virtual Surgery

Virtual surgery simulation is a virtual reality system used to simulate all kinds of phenomenon of surgery. For surgical simulation to be a useful training and simulation tool it must he realistic with respect to tissue deformation, tool interactions, visua rendering, force feedback and real-time response.As an interdiscipline research tcpic, virtual surgery incorporates the researches about Computer Science, Computer Graphics, Sensor Technology, Biomcchanics, Modem Medicine, Image Processing, Computer Vision, Robot Technology, Scientific Computing Visualization, etc. Using all of the above techniques we can implement the geometrical model, physical/compute model, collisior detection, real-time deformation (cutting, tearing etc), and realistic rendering of human soft tissue. The physical/compute modeling of soft tissue is one of the key techniques of surgery simulation. The research of it is dropped behind by other techniques because of the character of interdiscipline. It has become the bottleneck of surgery simulation research development.This thesis describe human soft tissue using topology of cavity organ for instance blood vessel, bladder, stomach, and intestines etc, and volume soft tissue for instance skin, fattiness, and muscles. Toward different surgery simulation request, we simplify human soft tissue to linear model, nonlinear model, or stiff/elastic model. Using stiffness coefficient, damping coefficient, and mass point density to represent the characters of stiff/elastic, anisotropy, and non homogenous of soft tissue.An unified soft t.ssue modeling method using mass-spring model was given in this paper. The soft tissues are discreted to a mass-spring-damper system, and the topologies of the system are described using adjacent tables, the dynamical equations can be constructed based on the data stored in the adjacent tables. The 4th order Runge-Kutta method is used to integrate the equations of deformation. Using computer graphical techniques to display the visual feedback of the deformation. Four examples of a surface model and a volumetric model to test the method are given.