Chirurgie virtuelle : modélisation temps réel des tissus mous, interactions et système haptique dédié

Abstract

The medical field is emerging recently some pedagogic simulators like what it exists from several years in other field like flight simulator or car driving simulator. Indeed, the current training of surgeons is performed on corpses (difficult, expensive and not practical) and companionship (with experienced surgeons). These difficulties involve a growing demand for surgical pedagogic simulators, especially in the field of mini-invasive surgery, with a consideration of gestures and tactile sensations. This thesis work, conducted in the Robotics Center(CAOR) of the Ecole des Mines de Paris, covers two important issues for achieving a surgical simulator: the real time soft tissue modeling and the realization of a haptic system dedicated to the virtual surgery. In order to model the deformable organ in real time, we conceive a physical method that offers the opportunity to parameterize our model starting from experimental measurements and to build a generic solution that can be applied to a wide variety of materials. Our approach consists of a synthesis between two kinds of presentation used in the field of continuum mechanics: the mass spring and the mass tensor. Our method is based on the Saint Venant Kirchhoff model which corresponds to a class of hyper-elastic materials. Once modelled, the body in ready to interact with the virtual environment. We, thus, propose some mechanisms for collisions detection with surgical tools and with the structure of the body itself. We propose also some mechanisms for collision management. A particular attention is given to the cutting mechanism that the body usually undergoes during surgery. In the second section, we present our design and realization of a force feedback system dedicated to the virtual surgery. It is a new design of the trocar, an essential tool for the mini-invasive surgery. We call it "active trocar". It is a 5 DOF force feedback system. Our system has a major advantage on what exists. It can be used for a large variety of endoscopic surgical operations because we it is based on the trocar and not on the endoscopic surgery tool. We optimized the design of this trocar in order to allow the use of several devices in the same virtual operation and evidently in order to guarantee good tactile effects. With this system, the surgeon is free to choice the suitable surgical tool and fit into in the trocar.