Virtual Reality-based Simulator for Regional Anaesthesia Block of the Lower Limbs Eckert, Jan Ullrich, Sebastian Frommen, Thorsten Fried, Eduard Virtual Reality Group, RWTH Aachen University E-Mail: jan.eckert@rwth-aachen.de Abstract: In this paper, we present a medical simulator for intuitive training of regional anaesthesia procedures in virtual environments. Novel data structures have been designed to represent the anatomy of virtual patients and a simulation framework has been created. The main contribution is the simulation of electric impulse transmission through soft tissue and nerve cords. Plausible interaction, visualization and basic haptic rendering ensure intu- itive usage of the simulator. As an example application, the scenario of a block of the lower limbs has been implemented. The resulting Virtual Reality-based simulation system is being evaluated by medical residents. Keywords: Medical Simulation, Visualization, Modeling, Virtual Human 1 Introduction In everyday practice at hospitals, it is necessary to treat patients with anaesthetics. Those are used to suppress the function of nerves, i.e., they temporarily switch off the ability to move and to feel pain. Global anaesthesia often causes unconsciousness, an intentionally induced state for major surgeries. Apart from implications to the sensory system, the inhibition of movement by applying anaesthetics to motoric nerves is essential for most surgeries. Any movement in the affected region reduces accuracy and the chance for success decisively. However, a global anaesthetization is often neither necessary nor wanted. It means a con- siderable amount of stress for the organism and may be fatal if the patient is not in a good physical condition. Regional anaesthesia (RA) is a less invasive alternative. With a specialized cannula, the anaesthetist is able to locate specific nerves. This cannula emits electric impulses which cause a physical feedback (twitches of muscles) if it is at close range to the nerve. After having located the nerves precisely enough, the aneasthetics are applied locally in this region. This kind of procedure needs much less aneasthetics and is a lesser burden on the human organism. Since the anaesthetist is not able to see the nerves nor can they be located by palpation, this procedure is more complex than global anaesthetization. Moreover, the specific path a nerve takes through the body may differ to a certain degree between different bodies. So the anaesthetist has to rely on fortunately well-known heuristics