A physiologically valid simulator for training residents to perform an epidural block

Describes the current status of the ongoing development of a virtual simulation system for use in training anesthesiology residents in the technique of delivering an epidural block. The system utilizes real-time graphics, a voice interface, and force-feedback applied to a Crawford needle to simulate a realistic epidural experience. The user sits in front of a SGI workstation and invokes the program through a voice interface. A computer generated image of the back, taken from MRI data, appears on the screen along with an image of the needle. The user places his hands on the physical needle, which is held by a 1 DOF Impulse Engine (developed by Immersion Corporation). As the physical needle is pushed in, the graphical representation of the needle moves in synchrony, and realistic forces are applied by the Impulse Engine to give the user the feel of actually inserting the needle into a patients back. The novice user can get feedback as to the position of the needle by watching an interactive view of the needle in a image showing the axial view of the MRI data of the patient's back. A more advanced user can request instantaneous axial, sagittal, or coronal MRI views of the position of the needle in the MRI data set using vocal commands. The haptic forces are currently being modeled from a combination of the MRI intensity values and expert opinion. Work in progress involves modeling these forces as springs, using the MRI intensity levels and a system of equations to quantitatively define the force for a given needle depth. A series of experiments are being planned to identify the true physiological forces involved in needle insertion. Results from these experiments will be used to develop the system of equations which will drive the force feedback on the simulator.