Computer-based simulations can be a powerful tool for training medical professionals by allowing them to learn and practice skills on realistic virtual patients before working with actual patients. Creating virtual reality medical simulations is challenging due to the complexity and precision of the techniques being simulated. Every aspect of the physical world cannot be simulated exactly, but it is key that the important aspects of the techniques are realistic.

The epidural needle insertion procedure is a common anesthesiology procedure in which the anesthesiologist inserts a needle into the epidural region of the back near the spinal cord in order to inject anesthetic medications. During this procedure, the anesthesiologist relies heavily on perception of force from the needle in order to visualize the tissue layers being penetrated.

The motivation for, and initial development of, a virtual reality simulator for the epidural needle insertion procedure is presented. A user study in which anesthesiologists used the initial simulator and qualitatively scored it's performance is presented. The results of this study indicated that the force-feedback models in the initial simulator did not feel realistic.

The main focus of the research was to create realistic feeling force-feedback models for a virtual-reality computer simulation of the epidural needle insertion procedure A force modeling methodology has been developed in which biomaterials testing was used to measure load displacement curves as needles were Inserted into biological specimens. High resolution MRI scans were performed prior to the biomaterials testing and registered to the needle insertion positions in order to Identify each layer the needle punctured.

Force models were developed for each type of tissue punctured during the epidural needle insertion procedure. These models were combined to create a generalized force model for the procedure. Force models were also developed for needle insertion into oranges.

Two virtual patients were developed from MRI data sets of two human subjects, an average female and a lean male. Four virtual oranges were also developed. A haptics-only computer simulator was developed which used a prototype force-feedback device on loan from Immersion Corporation.

The virtual oranges were used in a study to test the realism of force models developed through the force model development methodology. Two user studies were performed in which subjects directly compared needle puncture into physical oranges and virtual oranges in a blind randomized trial. The results of the studies indicate that the subjects could not differentiate between physical and virtual oranges.

A user study was planned to test for construct validity of the epidural simulator. Limitations of the hardware made this study infeasible, but planning the study did provide insight into future development issues.