3-D magnetic tracking of a single subminiature coil with a large 2-D array of uniaxial transmitters

A novel system and method for magnetic tracking of a single subminiature coil is described. The novelty of the method consists in employing a large, 8 × 8 array of coplanar transmitting coils. This allows us to always keep the receiving coil not far from the wide, flat transmitting array, to increase the signal-to-noise ratio, and to decrease the retransmitted interference. The whole transmitting array, 64 coils, is sequentially activated only at the initiation stage to compute the initial position of the receiving coil. The redundancy in the transmitters number provides fast and unambiguous convergence of the optimization algorithm. At the following tracking stages, a small (8 coils) transmitting subarray is activated. The relatively small subarray size allows us to keep a high update rate and resolution of tracking. For a 50-Hz update rate, the tracking resolution is not worse than 0.25 mm, 0.2° rms at a 200-mm height above the transmitting array´s center. This resolution corresponds to an ∼1-mm, 0.6° tracking accuracy. The novelty of the method consists as well in optimizing the transmitting coils´ geometry to substantially (down to 0.5 mm) reduce the systematic error caused by the inaccuracy of the dipole field approximation.