Search

In this paper, we investigate the physical accuracy of the 3D mass-spring-damper (MSD) model of an isotropic object. The isotropic object should have the same Poisson constant and Young's modulus in different directions, and so should its model. Based on these two properties, we derive a set of constraints on the parameters of the 3D MSD model. From these constraints, the parameters of the MSD model can be obtained by the constrained least square method. For the MSD model with tetrahedral meshes, we show that its tensile stiffness can be achieved very accurately, and the prone irregular Poisson effects can be suppressed below a tolerable level although its Poisson constant generally cannot be precisely achieved. For the MSD model with hexahedral meshes, we find that the parameters of the model can be obtained explicitly in terms of material properties and mesh geometry. In this case, we also demonstrate that both the tensile stiffness and the Poisson constant can be accurately achieved.

Haptic modeling of organs using existing approaches is still not realistic or real time. We propose and develop the mathematical foundation of a new approach to modeling organs using beams. Beams are well known entities in Civil and Structural engineering. We develop their mathematical properties in the context of organ simulation. The real time advantage arises from the fact that a single beam implementation eliminates hundreds, if not thousands of mass springs from the traditional mass spring models and, thousands of polygons from the finite element method. Even more importantly, our derivation is valid for large deformation. Most previous work has developed equations only for small deflections. Large deformation is important because we set out to simulate blunt cutting which requires models for large deflections. Our new model, when simulated and compared with an FEM model provides comparable accuracy.

The simulation of catheter, guide wire, rigid tissues, muscles and blood vessels using conventional methods like mass spring model and FEM are computationally expensive. The former is comparatively faster than the latter but less accurate. Earlier, we proposed a new method of simulating of tubular organs using deformable beam models. This method is not only accurate but also promises to be faster than mass-spring model for the simulation of tissues. This paper focuses on an important aspect of this approach--the determination of key and driving points of a beam model.

In this paper we use the 2D angular spring based mass-spring-damper (AMSD) model to simulate the plastic mesh in a laparoscopic hernia surgery simulator. We propose a physically based method to systematically derive the optimal parameters of the 2D AMSD model. While the traditional 2D MSD model lacks resistance against bending, the 2D AMSD model with optimized parameters can provide correct bending resistance as well as stretching resistance. The simulated mesh is demonstrated to be much more realistic.

Visual realism in laparoscopic surgery simulation is very desirable. Previously, much work has been done to extract the organs and textures from the visible human data (VHD) using various rendering techniques. We present here a technique to extract the true texture from visible human data for the laparoscopic herniorrhaphy simulation. A VHD slice provides texture only in the direction in which it was visualized whereas the surgeons visualize the facet of an organ during a laparoscopic surgery. Our paper describes an approach for the extraction and mapping facet texture from the VHD.

The growing interest in laparoscopic hernia surgery and in surgical simulators has motivated our current research. In this paper, we present our work in simulating the process of stapling used in laparoscopic herniorrhaphy. By connecting two separate deformable preperitoneal meshes together, our model has simulated the repair process for a bilateral hernia correction. The task of mesh placement and stapling of corners was simulated, to allow surgeons to practice their hand-eye coordination. Various deformable models and numerical methods were researched to comply with the real time requirements. The stapling simulator can either be independently used as a part-task (sub-task) trainer or be integrated as a module of a complete VR-based simulator. A phantom device was used to provide haptic-based force feedback during task rehearsals.

Simulation of cauterization and irrigation forms an important part of a virtual laparoscopic trainer. Typically, they are carried out to stop the intragastric bleeding due to an accidental cut by the surgeon. In this paper, we present a method to simulate these special visual effects in an integrated fashion in real-time. We have simulated cauterization and irrigation using a particle-based system. A physics-based model is used to simulate accumulation and removal of fluids. The integrated special effects were implemented and tested in a prototype environment.