Particle methods for a virtual patient

The particle systems approach is a well known technique in computer graphics for modelling fuzzy objects such as fire and clouds. The algorithm has also been applied to different biomedical applications and this paper presents two such methods: a charged particle method for soft tissue deformation with integrated haptics; and a blood flow visualization technique based on boids. The goal is real time performance with high fidelity results

Instrument-tissue segment interaction using finite element modeling

Los Alamitos, C

Implicit Representations of the Human Intestines for Surgery Simulation

International audienceIn this paper, we propose a modeling of the intestines by implicit surfaces for abdominal surgery simulation. The difficulty of such a simulation comes from the animation of the intestines. As a matter of fact, the intestines are a very long tube that is not isotropically elastic, and that bends over itself at various spots, creating multiple self-contacts. We use a multiple component model for the intestines: The first component is a mechanical model of their axis; the second component is a specific sphere-based model to manage collisions and self-collisions; and the third component is a skinning model to define their volume. This paper focuses on the better representation for skinning the intestines. We compare two implicit models: Surfaces defined by point-skeletons and convolution surfaces. A direct application of this simulation is the training of a typical surgical gesture to move apart the intestines in order to reach certain areas of the abdomen

Generation of flexible 3D objects

The objective of this research is to develop a tool for the generation of 3D objects modeled with flexible materials, with visco-elastic or inelastic characteristics, similar to the plasticine. It is desirable to prioritize the simplicity of the interface with the user in the interactive deformation process of the object. To compute the deformations of object which is exposed to external forces, like elements with which the modeling will be simulated, what implies the process between the deformable object and rigid ones.Facultad de Informátic

Virtual Reality Interactive Design Utilizing Meshless Stress Re-Analysis

Interactive design gives engineers the ability to modify the shape of a part and immediately see the changes in the part’s stress state. Virtual reality techniques are utilized to make the process more intuitive and collaborative. The results of a meshless stress analysis are superimposed on the original design. As the engineer modifies the design using subdivision volume free-form deformation, the stress state for the modified design is computed using a Taylor series approximation. When the designer requests a more accurate analysis, a stress re-analysis technique based on the pre-conditioned conjugate gradient method is used with parallel processing to quickly compute an accurate approximation of the stresses for the new design

An error estimator for real-time simulators based on model order reduction

Model order reduction (MOR) is one of the most appealing choices for real-time simulation of non-linear solids. In this work a method is presented in which real time performance is achieved by means of the o-line solution of a (high dimensional) parametric problem that provides a sort of response surface or computational vademecum. This solution is then evaluated in real-time at feedback rates compatible with haptic devices, for instance (i.e., more than 1kHz). This high dimensional problem can be solved without the limitations imposed by the curse of dimensionality by employing Proper Generalized Decomposition (PGD) methods. Essentially, PGD assumes a separated representation for the essential eld of the problem. Here, an error estimator is proposed for this type of solutions that takes into account the non-linear character of the studied problems. This error estimator allows to compute the necessary number of modes employed to obtain an approximation to the solution within a prescribed error tolerance in a given quantity of interest

Simulation of Endoscopic Surgery

International audienceThis paper describes preliminary work on virtual reality technology applied to liver surgery and proposes several enhancements leading towards realistic surgical simulation. We have built a realistic model of the liver, including the capsule and the four internal arborescences, from a complete set of slice images. A linear elastic biomechanical model was computed using a finite elements method (FEM). This task was performed off line, by pre-computing all possible deformations and force reactions. This approach allows real-time interaction during the simulation. The user interaction is effected by a set of mechanical devices, representing laparoscopic instruments. This haptic interface allows the surgeon to feel the contact forces exerted by the virtual deformable liver-model. The main medical applications of the simulator are in surgical planning, teaching and training. The combination of surgical planning and simulation will lead to improved intervention efficiency and optimal care delivery