Method of calibrating combined field location and MRI tracking

1. A method of calibrating field location tracking to magnetic resonance tracking comprising:

providing a composite tracking system for tracking movement of a medical device within a patient volume, the composite tracking system including a field location tracking system having at least one field location sensor structured to be coupled to the medical device, a magnetic resonance tracking system having at least one tracking coil structured to be coupled to the medical device, and a composite tracking processor operably coupled to the field location tracking system and the magnetic resonance tracking system, said composite tracking processor for receiving and processing a plurality of field location parameters from the field location tracking system and a plurality of positional coordinates from the magnetic resonance tracking system;

moving the medical device with the field location sensor and at least one tracking coil coupled thereto throughout a plurality of points within the patient volume to generate the plurality of field location parameters and the plurality of positional coordinates;

causing said composite tracking processor to receive the plurality of positional coordinates from said magnetic resonance tracking system and calculate a plurality of magnetic resonance tracking locations;

causing said composite tracking processor to receive and process the plurality of field location parameters from the field location tracking system and determine a plurality of field location parameters that correspond to the plurality of magnetic resonance tracking locations;

causing said composite tracking processor to generate a transfer function for mapping the field location parameters from the field location tracking system to the corresponding positional coordinates of the magnetic resonance tracking system to registers a field location coordinate system to a magnetic resonance coordinate system; and

causing said composite tracking processor to determine a present location of the field location sensor by applying the transfer function.

2. The method of claim 1 , wherein the field location parameters are selected from voltage, impedance, electrical current, time delay, sound intensity and combinations of the foregoing.

3. The method of claim 1 further comprising using the transfer function to calculate an estimated location of the medical device in the magnetic resonance coordinate system.

4. The method of claim 1 , wherein a plurality of field location sources comprising electrodes operable to create an electric field along three separate axes in three-dimensional space, said field location sources operably coupled to the field location tracking system.

5. The method of claim 1 , wherein each of the magnetic resonance tracking locations and the field location parameters comprises an x-location value, a y-location value, and a z-location value that together provide location in three-dimensional space.

6. The method of claim 5 , wherein the estimated x-, y-, and z-locations of the medical device in the magnetic resonance coordinate system are calculated using interpolation or extrapolation.

7. The method of claim 6 , wherein the interpolation or extrapolation is linear or polynomial.

8. The method of claim 5 , further comprising storing each of the magnetic resonance tracking locations and the corresponding field location parameters as a data set, the number of data sets being equal to the number of calculated magnetic resonance tracking locations.

9. The method of claim 8 further comprising ordering the data sets in monotonically increasing order said data sets forming multidimensional coordinate sets including x-location parameter values, x-location values, y-location parameter values, y-location values, z-location parameter values, and z-location values.

10. The method of claim 9 , wherein the transfer function comprises a three-dimensional mapping.

11. The method of claim 10 , further comprising measuring a field location parameter of the medical device, the field location parameter including an x-location parameter value, a y-location parameter value, and a z-location parameter value and using the three-dimensional mapping to calculate an estimated x-location of the medical device in the magnetic resonance coordinate system, an estimated y-location of the medical device in the magnetic resonance coordinate system, and an estimated z-location of the medical device in the magnetic resonance coordinate system, wherein the estimated x-, y-, and z-locations represent a three-dimensional location of the medical device in the magnetic resonance coordinate system.

12. The method of claim 11 , wherein the estimated x-, y-, and z-locations of the medical device in the magnetic resonance coordinate system are calculated using interpolation or extrapolation.

13. The method of claim 12 , wherein the interpolation or extrapolation is linear or polynomial.