An apparatus for monitoring a nerve includes a Foley type catheter having an exterior surface, and first and second pairs of ring electrodes formed on the exterior surface of the Foley catheter. The tunnel has an upper surface and a portion extending rearwardly beyond the seat. A digital display indicates the currently predetermined cooking stage for the currently selected cooking zone. In practice, an initial weight factor table is provided. The magnetic microspheres can be sorted into a number of distinct populations, each population with a specific range of magnetic moments and different receptor agents can be attached to each distinct population of magnetic microsphere.