Tracking three dimensional ultrasound with immunity from ferro-magnetic interference

Magnetic field tracking devices offer many advantages over other methods for tracking transducer location and orientation during ultrasound image acquisition. The disadvantage is sensitivity to ferromagnetic interference. We evaluated an "immune" tracking device that uses a flat plate magnetic field transmitter to shield the tracking volume from interference from the hospital bed. When we compared its accuracy with that of Ascension Technology, Inc.'s Flock of Birds(TM), we found that the immune device performed as well on a hospital bed as the Bird in a control environment. We conclude that the flat plate transmitter enables three-dimensional ultrasound by the freehand scanning approach in a clinical environment.