A system for combining electromagnetic position and orientation tracking
with magnetic resonance scanner is provided. One embodiment includes a
magnetic resonance scanner defining a reference coordinate system for
scanning a target. Coupled to the magnetic resonance scanner is a magnetic
field source which produces a magnetic field. The magnetic field is sensed
by a magnetic field sensor which produces a signal proportional to the
magnetic field. The magnetic field sensor has a location relative to the
reference coordinate system. The location of the magnetic field sensor
relative to the reference coordinate system of the magnetic resonance
scanner is determined by a location tracking device using at least a line
segment model of the magnetic field source and the signal from the
magnetic field sensor.