Endoscopic surgery simulator Virgy interconnects distant doctors and students for training

Lausanne 11 August 1998 Since a few years, researchers of the VRAI (Virtual Reality and Active Interface) Group at the Swiss Federal Institute of Technology, are working on the development of a laparoscopic surgery training system. The project, called Virgy, consists of two complementary design phases. The first one relates to the creation of a virtual environment by means of the Libptk, a 3D graphic sensor engine which generates the population of all the objects in the simulation. A so-called surgical ghost provides the physician with force feedback through the endoscopic tools, that are used for manipulation of the virtual organs. The second phase involves a multimedia communication platform, allowing surgeons at remote locations to co-operate and offering students an opportunity for distant learning.

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Since a few years, researchers of the VRAI (Virtual Reality and Active Interface) Group at the Swiss Federal Institute of Technology, are working on the development of a laparoscopic surgery training system. The project, called Virgy, consists of two complementary design phases. The first one relates to the creation of a virtual environment by means of the Libptk, a 3D graphic sensor engine which generates the population of all the objects in the simulation. A so-called surgical ghost provides the physician with force feedback through the endoscopic tools, that are used for manipulation of the virtual organs. The second phase involves a multimedia communication platform, allowing surgeons at remote locations to co-operate and offering students an opportunity for distant learning.

The scene, which simulates the interactions between the surgical instruments and the gastro-intestinal organs, is described in a file. The engine loads the programme at initialization time, thus enabling the same software to run various types of real time simulations, like for instance the monitoring and controlling of several remote mobile robots. The independent objects that are part of the population in the description file, might be rendered solids, textures, deformation modules, sensors or other elements. Since they inherit a range of basic features from the same root class, they can react to external events, load or store themselves from or into a file, provide a control panel, and exchange messages. In this way, the Virgy simulator disposes of a huge library of hierarchically ranged, flexible objects.

Each graphic component, whether a surgical tool or a virtual organ, can be linked to a positioning device. In turn, this sensor connects to the external world in two possible ways, whether through local communication ports or through the Open Agent Architecture (OAA). As a result, sensors can be shared simultaneously by several people at different locations via network links. Trainees and surgeons are able to use 3D mice, force feedback tools, computer pens, stereographic 3D vision systems or even speech recognizers in order to instruct the computer to reset the position of a solid or a view point. The user can equally introduce other modifications in the virtual scene, by changing the way a texture is applied to a solid through animated texture mapping. Thus, dynamic effects such as pulsations or vibrations are simulated.

Profiles are used to compute real time deformation of a virtual organ touched by a surgical tool. The Swiss researchers have designed the PantoScope to offer haptic feedback in four degrees of freedom. This parallel-serial force reflecting mechanism enables simulation over a wide dynamic range of object attributes, such as weight, elasticity and viscosity. In order to enhance the realism, the spherical remote-centre-of-motion force feedback manipulator is completely hidden below the skin of the artificial patient. The team's current occupation involves the integration of physical properties, like bleeding, the removal of fat tissues, and gravity into the surgery training system. You can follow the ongoing work at the Web site of the Virgy project.


Leslie Versweyveld

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