INTEGRATING BIOMECHANICAL PARAMETERS IN MODELING OF LIVER WITH AND WITHOUT TUMOR IN VIRTUAL ENVIRONMENT

Abstract

One of the fundamental components of a surgical simulator is a deformable object. Two main approaches used in surgical simulation to model deformable objects are Finite Element Model (FEM) and Mass Spring Model (MSM). MSM is often preferred due to its simplicity and low computational cost. However, setting of appropriate model parameters such as mass, spring stiffness and damping coefficients in order to reproduce mechanical responses remains an issue. In this paper, biomechanical parameters (Poisson’s values, density) are integrated into MSM based on a tetrahedral structured network in modeling of liver with and without tumor. For the identification of parameters in a real time surgical simulation, Barycentric mass lumping, Lloyd’s approach, Rayleigh formula and Fourth order Runge-Kutta integration method are used to determine the node mass, spring stiffness, damping coefficient and suitable time step respectively. The resulted node mass, spring stiffness and damping coefficient for liver without tumor and with tumor are 1.9825kg, 5.4225 kPa, 7.4525 N/m2 and 5.9256kg, 7.0484 kPa, 11.9012 N/m2 respectively. These values are substituted into MSM, which is then visualized in CHAI 3D ensuring the performance required by a real time simulation. Finally, comparison between the liver with and without tumor in terms of mass, spring stiffness, and damping constant is highlighted.