Electromagnetic tracking method and system

• US 20080238413A1
• Filed: 03/26/2007
• Published: 10/02/2008
• Est. Priority Date: 03/26/2007
• Status: Active Grant

• Current Assignee: Stryker European Operations Holdings, LLC (Stryker Corporation)
• Original Assignee: General Electric Company
• Inventors: Anderson, Peter Traneus
• Granted Patent: US 7,902,817 B2
• Time in Patent Office: Days
• US Class Current: 324/207.17
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004
• CPC Class Codes: G01B 7/30 for measuring angles or tapers; for testing the alignment of axes

Abstract

Provided is an electromagnetic tracking system, comprising a coil arrangement comprising a first coil configured to generate a first magnetic field and a second coil configured to generate a second magnetic field and a drive unit configured to provide a first drive current to the first coil and to provide a second drive current to the second coil, wherein the first drive current and the second drive current are at about the same frequency, wherein the frequency is below 60 Hz, and wherein the first electromagnetic field and the second magnetic field are generated out of phase. Also provided is a method of electromagnetic tracking comprising generating a first electromagnetic field at a frequency, generating a second electromagnetic field at about the frequency, wherein the frequency is below 60 Hz and wherein the first electromagnetic field and the second magnetic field are generated out of phase, sensing the first electromagnetic field and the second electromagnetic field and processing a waveform indicative of a combination of the sensed first electromagnetic field and the sensed second electromagnetic field.

Claims

1. An electromagnetic tracking system, comprising:

a coil arrangement comprising a first coil configured to generate a first magnetic field and a second coil configured to generate a second magnetic field; and

a drive unit configured to provide a first drive current to the first coil and to provide a second drive current to the second coil,

wherein the first drive current and the second drive current are at about the same frequency, wherein the frequency is below 60 Hz, and wherein the first electromagnetic field and the second magnetic field are generated out of phase.

2. The electromagnetic tracking system of claim 1, and wherein the first drive current is out of phase with the second drive current.

3. The electromagnetic tracking system of claim 1, wherein the first drive current comprises a sine wave current, and the second drive current comprises a cosine wave current approximately 90 degrees out of phase with the first drive current.

4. The electromagnetic tracking system of claim 1, wherein the first coil and the second coil are of the same orientation relative to a vector that connects a center of the first coil and a center of the second coil.

5. The electromagnetic tracking system of claim 1, wherein the first coil and the second coil are tilted at approximately 54.7 degrees from a vector that connects a center of the first coil and a center of the second coil.

6. The system for electromagnetic tracking of claim 1, wherein the magnitude of a moment of the first magnetic field is different from the magnitude of a moment of the second magnetic field.

7. The system for electromagnetic tracking of claim 6, wherein a ratio of the magnitude of the moment of the first magnetic field to the magnitude of the moment of the second magnetic field comprise an approximate range of 1.4 to 2.

8. The system for electromagnetic tracking of claim 1, comprising at least one receiver configured to receive the first magnetic field and the second magnetic field generated by the coil arrangement.

9. The system for electromagnetic tracking of claim 8, comprising a processor configured to determine a position and/or orientation of the first coil and the second coil based on the first magnetic field and the second magnetic field received by the at least one receiver.

10. The system for electromagnetic tracking of claim 1, wherein the coil arrangement is coupled to an instrument.

11. A method for electromagnetic tracking, comprising:

driving a first current across a first coil to generate a first magnetic field;

driving a second current across a second coil to generate a second magnetic field,

wherein the first magnetic field and the second magnetic field are at about the same frequency, wherein the frequency is below 60 Hz, and wherein the first magnetic field is out of phase with the second magnetic field;

sensing the first magnetic field and the second magnetic field with at least one electromagnetic receiver; and

processing the sensed first magnetic field and the sensed second magnetic field.

12. The method of claim 11, wherein driving a first current comprises providing a sine waveform current and driving a second current comprises providing a cosine waveform current approximately 90 degrees out of phase with the first drive current.

13. The method of claim 11, wherein the first coil and the second coil are of the same orientation relative to a vector that connects a center of the first coil and a center of the second coil.

14. The method of claim 11, wherein the first coil and the second coil are tilted at an angle of approximately 54.7 degrees from a vector that connects a center of the first coil and a center of the second coil.

15. The method of claim 11, wherein the magnitude of a moment of the first magnetic field is different from the magnitude of a moment of the second magnetic field.

16. The method of claim 15, wherein a ratio of the magnitude of the moment of the first magnetic field to the magnitude of the moment of the second magnetic field comprise an approximate range of 1.4 to 2.

17. The method of claim 11, wherein sensing the first magnetic field and the second magnetic field comprises measuring mutual inductance between the first coil and the at least one electromagnetic receiver, and measuring mutual inductance between the second coil and the at least one electromagnetic receiver.

18. The method of claim 11, wherein processing the sensed first magnetic field and the sensed second magnetic field comprises determining a position and/or orientation of the first coil transmitter and/or the second coil relative to the at least one electromagnetic receivers.

19. The method of claim 11, comprising positioning an instrument with respect to the receiving array, wherein the first coil and the second coil are coupled to the instrument.

20. A method of electromagnetic tracking comprising:

generating a first electromagnetic field at a frequency;

generating a second electromagnetic field at about the frequency, wherein the frequency is below 60 Hz and wherein the first electromagnetic field and the second magnetic field are generated out of phase;

sensing the first electromagnetic field and the second electromagnetic field; and

processing a waveform indicative of a combination of the sensed first electromagnetic field and the sensed second electromagnetic field.

21. The method of claim 20, wherein processing the waveform comprises using the waveform to determine an averaged position of the source of the first electromagnetic field and the source of the second electromagnetic field.

22. The method of claim 21, comprising calculating a goodness-of-fit based on the averaged position of the source of the first electromagnetic field and the source of the second electromagnetic field.

23. The method of claim 20, wherein processing the waveform comprises calculating a goodness-of-fit based on varying the phases of the first electromagnetic field and the second electromagnetic field to identify the generated phases of the first first electromagnetic field and the second electromagnetic field, and identifying mutual inductance of the first electromagnetic field and the second electromagnetic field based on their respective phases.

24. The method of claim 20, wherein processing comprises identifying a source of the first magnetic field and a source of the second magnetic field by comparing the magnitude of the moment vector of the sensed first magnetic field and the sensed second magnetic field.