Philippe Meseure

A Suture Model for Surgical Simulation

In this paper, we propose a surgical thread model in order for surgeons to practice a suturing task. We first model the thread as a spline animated by continuous mechanics. The suture is simulated via so-called “sliding point” constraints, which allow the spline to move freely while constrained to pass through specific piercing points. The direction of the spline at these points can also be imposed. Moreover, to enhance realism, an adapted model of friction is proposed, which allows the thread to remain fixed at the piercing point or slides through it. Our model yields to good results showing realistic behavior, robust computation and interactive rates.

Adaptive resolution of 1D mechanical B-spline

This article presents an adaptive approach to B-spline curve physical simulation. We combine geometric refinement and coarsening techniques with an appropriate continuous mechanical model. We thus deal with the (temporal and geometric) continuity issues implied when mechanical adaptive resolution is used. To achieve real-time local adaptation of spline curves, some criteria and optimizations are shown. Among application examples, real-time knot tying is presented, and curve cutting is also pointed out as a nice side-effect of the adaptive resolution animation framework.

Simulator for laser photocoagulation in ophthalmology

The practice of laser photocoagulation plays a major role in ocular therapy, but the persistence of many postoperative complications denotes genuine difficulty in mastering the technique. The authors present a device which, thanks to the use of simulation, enables actual practice to be dissociated from apprenticeship. While complying with the constraints of realism with regard to habitual conditions of laser use, the device offers access to a wide variety of clinical situations. The apparatus is built around the traditional instrument. A virtual image of the fundus is produced in real time from the sensors which detect the actual gestures used. The calculations make use of textured geometrical models. Digitized color photographs are organized to form a database which reflects the diversity of pigmentations and pathologies. A software interface has been developed to facilitate the use of the device. The prototype is operated using a PC-compatible computer; it displays the images at the rate of at least seven per second on a miniature CGA screen incorporated in the slit-lamp. It is currently being validated for clinical applications. Above and beyond apprenticeship in laser photocoagulation, its potential applications extend to the entire field of ophthalmological symptomatology and, more broadly, to the simulation of any examination conducted with the help of binocular or endoscopic optics.<<ETX>>

Improving ZRP performance by taking into account quality of links

MANET are characterized by their limited bandwidth and high packet error rate. In mobility, multi-path and shared bandwidth contexts, routing protocols play a major role. On-demand routing approaches lead to high delay while, in link-state protocols, controls messages broadcasting consumes much bandwidth. Hybrid protocols such as Zone Routing Protocol (ZRP) attempt to exploit the advantages of both approaches. It uses limited scope proactive approach to maintain routes towards a surrounding zone and reactive approach to communicate with farther destinations. For a better exploitation of network capabilities, we propose a Binary Error Rate (BER) based approach of ZRP (BER-ZRP). With BER-ZRP, all phases of link-state recording and routing tables calculation are under Quality of Service control so that better paths in terms of BER are preferred. The overhead induced by route maintenance and route discovery processes is better managed. This approach allows to improve ZRP Packet Delivery Ratio and Normalized Oversize Load.

A new BER-based approach to improve OLSR protocol

This paper presents a method to enhance OLSR quality of service. Our approach heavily relies on the binary error rate metric and allows to rise the packet delivery ratio (PDR). We find that two elements of OLSR must be changed, the MPR selection algorithm and the route computation. We show that our approach provides better PDR than the original OLSR algorithm.

SOPHOCLE: A Retinal Laser Photocoagulation Simulator: Overview

Retinal laser photocoagulation has been used for a decade, but no real improvement in results has been observed.The simulator described in this paper, by separating actual practice from apprenticeship, allows one both to learn how to manipulate the equipment and to train oneself for making a diagnosis and operating. It has been designed as close as possible to the actual operation conditions and gives the opportunity to deal with a large library of current or rare cases. An actual slit-lamp is supplied with sensors measuring all the degrees of freedom of the system. The images are calculated by a PC computer and are displayed on a miniature screen placed inside the binocular. A user interface is provided through a Computer Assisted Training software, which allows users to manage the pigmentations and pathologies data base, to follow the students skill level and to prepare critical operations.

Generalized maps for erosion and sedimentation simulation

Abstract We propose a new approach, based on dynamic animation, to simulate geomorphological events such as erosion, sediment transportation and deposition. It relies on a generalized map representation of different geological layers. The topological evolution of these layers is driven by a set of displacements applied onto the vertices. The topological consistency of the model is guaranteed by a collision detection system that handles vertices, edges, or faces through generic operations. Experimental results show the ability of this approach to simulate various evolution scenarios studied in geology. Fluid simulation is added to implement fluid–solid interactions based on a hydrology model. These interactions generate animations of hydraulic erosion and sedimentation phenomena.

A Topology-based Animation Model for the Description of 2D Models with a Dynamic Structure

This paper presents a model that describes the temporal evolution of 2D-topological structures to represent and control dynamic natural phenomena. As input, the user provides the system with a list of actions that gives a high-level description of the evolution in terms of application-specific operations. As output, a complete representation of the evolution is computed. Our model is composed of three parts: A structural model allowing the temporal representation of both topology and geometry; an event model that aims at detecting topological modifications and ensures consistency between topology and geometry; and a semantic model that simultaneously describes the evolution as a sequence of elementary modifications and manages the history of the various entities of the model. We show the efficiency of the model in the geology field, by studying two well-known phenomena, namely sedimentation and erosion.

Topology-based Physical Simulation

This paper presents a framework to design mechanical models relying on a topological basis. Whereas naive topological models such as adjacency graphs provide low topological control, the use of efficient topological models such as generalized maps guarantees the quasi-manifold property of the manipulated object: Topological inquiries or changes can be handled robustly and allow the model designer to focus on mechanical aspects. Even if the topology structure is more detailed and consumes more memory, we show that an efficient implementation does not impact computation time and still enables real-time simulation and interaction. We analyze how a simple mass/spring model can be embedded within this framework.

Topology-based abstraction of complex biological systems: application to the Golgi apparatus

Many complex cellular processes involve major changes in topology and geometry. We have developed a method using topology-based geometric modelling in which the edge labels of an n-dimensional generalized map (a subclass of graphs) represent the relations between neighbouring biological compartments. We illustrate our method using two topological models of the Golgi apparatus. These models can be animated using transformation rules, which depend on geometric and/or biochemical data and which modify both these data and the topology. Both models constitute plausible topological representations of the Golgi apparatus, but only the model based on a recent hypothesis about the Golgi apparatus is fully compatible with data from electron microscopy. Finally, we outline how our method may help biologists to choose between different hypotheses.