1. A system for displaying relative positions of two structures during a procedure on a body, the system comprising: memory for storing an image data set representing the position of the body based on scans of the body, the image data set having a plurality of data points in known relation to a plurality of reference points for the body; a magnetic field generator for generating a magnetic field to be sensed by one or more magnetic field sensors placed in known relation to the reference points of the body for detecting the magnetic field and for generating positional signals in response to the detected magnetic field; a processor for receiving the reference signals and for ascertaining a location of the magnetic field sensors based upon the reference signals, the processor for generating a displaced image data set representing the relative positions of the body elements during the procedure; and a display utilizing the displaced image data set generated by the processor to display the relative position of the body elements during the procedure.