Method and system for navigating a catheter probe in the presence of field-influencing objects

• US 6,493,573 B1
• Filed: 06/08/2000
• Issued: 12/10/2002
• Est. Priority Date: 10/28/1999
• Status: Expired due to Term

• Current Assignee: Surgical Navigation Technologies, Inc. (Medtronic Plc)
• Original Assignee: Enterprise Medical Technology, Inc., Winchester Development Associates
• Inventors: Martinelli, Michael A., Kessman, Paul, Jascob, Brad
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): Lin, Jeoyuh
• Application Number:
  US09/589,779
• Time in Patent Office: 915 Days
• Field of Search: 600/407, 600/409, 600/410, 600/411, 600/422, 600/423, 600/424, 600/433, 600/434, 324/301, 324/302, 324/244, 324/245, 324/246, 324/247, 324/256, 324/257, 324/258, 324/259, 128/899
• US Class Current: 600/424
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• CPC Class Codes: A61B 2034/2072 Reference field transducer attached to an instrument or patient
• CPC Class Codes: A61B 2090/0481 against EM radiation, e.g. microwave
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 34/70 Manipulators specially adapted for use in surgery
• CPC Class Codes: A61B 90/36 Image-producing devices or illumination devices not otherwise provided for

Abstract

A system for and method of determining and compensating for the effect of a field influencing object on a field sensor, preferably a coil, that is within a navigational domain. The navigational domain contains navigational magnetic energy and disturbing magnetic energy, and the field influencing object produces the disturbing magnetic energy in response to the navigational magnetic energy. The correction system includes a first transmitter for projecting into the navigational domain field energy in a first waveform sufficient to induce a first signal value in the sensing coil. The system also includes a second transmitter for projecting into the navigational domain field energy in a second waveform sufficient to induce a second signal value in the sensing coil. The system further includes a signal processor for receiving the first signal value and for receiving the second signal value to determine the effect of the electrically conductive object on the field senior. In other embodiments, the correction system may utilize a second sensing coil to receive and process an alternate aspect of the field energy from a position that is different from the first field sensor, or the system may utilize a storage device that contains information relating to the effect of the field influencing device within the navigational domain.

Claims

1. A correction system for determining an effect of at least one interfering object on a field sensor within a navigational domain, the system comprising:

a first transmitter configured to project, into said navigational domain, field energy in a first waveform at a first frequency sufficient to induce a first desired signal value in said field sensor from said first transmitter and a first disturbance signal value in said field sensor from said at least one interfering object;

a second transmitter configured to project, into said navigational domain, field energy in a second waveform at a second frequency sufficient to induce a second desired signal value in said field sensor from said second transmitter and a second disturbance signal value in said field sensor from said at least one interfering object; and

,

a signal processor configured to receive said first desired and disturbance signal values and said second desired and disturbance signal values and to determine influences of said at least one interfering object on said field sensor from said first and second disturbance signal values, to thereby permit a substantially precise location of said field sensor to be determined despite the presence of said at least one interfering object.

2. The correction system of claim 1, wherein said field energy is magnetic field energy.

3. The correction system of claim 1, wherein said at least one interfering object is an electrically conductive object.

4. The correction system of claim 1, wherein said field sensor includes an electrically conductive sensing coil.

5. The correction system of claim 4, wherein said field sensor includes only a single electrically conductive sensing coil.

6. The correction system of claim 1, wherein said first waveform is a sinusoidal waveform, and

wherein said second waveform is a sinusoidal waveform.

7. The correction system according to claim 6, wherein said first transmitter and said second transmitter include (i) three unidirectional coil sets, each said set being driven by a drive unit capable of driving said unidirectional coil set at said first frequency and at said second frequency, and (ii) six delta coil sets, each said set being driven by a drive unit capable of driving said delta coil set at said first frequency and said second frequency, such that said three unidirectional coil sets and said six delta coils sets produce said field energy at said first and second frequencies.

8. The correction system according to claim 7, wherein said three unidirectional coil sets include a first unidirectional coil set oriented so as to produce a substantially uniform amplitude field directed in an x direction, a second unidirectional coil set oriented so as to produce a substantially uniform amplitude field directed in a y direction, and a third unidirectional coil set oriented so as to produce a substantially uniform amplitude field directed in a z direction, such that said x, y and z directions are substantially mutually orthogonal.

9. The correction system according to claim 8, wherein said first unidirectional coil set having (i) a first coil pair including a first coil element and a second coil element and (ii) a second coil pair including a third coil element and a fourth coil element, said first coil element and said third coil element being disposed in a major surface of a platform, said second coil element being disposed in a first lateral wall of said platform, and said first lateral wall and said second lateral wall are substantially normal to said major surface and substantially parallel to one another.

10. The correction system according to claim 8, wherein said second unidirectional coil set having a first coil element and a second coil element disposed within a platform, said coil elements being spaced apart and substantially parallel to one another.

11. The correction system according to claim 8, wherein said third undirectional coil set having (i) a first coil pair including a first coil element and a second coil element, and (ii) a second coil pair including a third coil element and a fourth coil element, said first coil element and said third coil element being disposed in a major surface of a platform, said second soil element being disposed in a first lateral wall of said platform, and said fourth coil element being disposed in a second lateral wall of said platform, wherein said first lateral wall and said second lateral wall are substantially normal to said major surface and substantially parallel to one another.

15. The correction system of claim 7, wherein said signal processor comprises:

(i) a first sequencer configured to (a) sequentially activate each of said three unidirectional coil sets and said six delta coil sets at said first frequency, and to measure said first desired and disturbance signal values corresponding to each of said unidirectional and delta coil sets at said first frequency, and (b) to sequentially activate each of said three unidirectional coil sets and said six delta coil sets at said second frequency, and to measure said second desired and disturbance signal values corresponding to each of said unidirectional and delta coil sets at said second frequency; and

,

(ii) a processor configured to calculate, for each of said unidirectional and delta coil sets, an adjusted signal value as a predetermined function of said first desired and disturbance signal values and said second desired and disturbance signal values, so as to produce nine adjusted signal values, each corresponding to field energy from one of said unidirectional coil sets and said delta coil sets.

16. The correction system according to claim 1, further including a third transmitter configured to project into said navigational domain a third waveform sufficient to induce third desired and disturbance signal values in said field coil, said third desired and disturbance signal values being influenced by said at least one interfering object;

and

wherein said signal processor is further configured to receive said third desired and disturbance signal values.

17. The correction system according to claim 16, further including a fourth transmitter configured to project into said navigational domain a fourth waveform sufficient to induce fourth desired and disturbance signal values in said field coil, said fourth desired and disturbance signal values being influenced by said at least one interfering object;

and

wherein said signal processor is further configured to receive said fourth desired and disturbance signal values.

18. The correction system according to claim 17, further including N-4 transmitters configured to project into said navigational domain N waveforms sufficient to induce N desired and disturbance signal values in said field coil, said N signal values being influenced by said at least one interfering object;

and

wherein said signal processor is further configured to receive N desired and disturbance signal values.

19. The correction system according to claim 1, wherein for each additional interfering object within said navigational domain, an additional field energy in an additional waveform at an additional frequency is required to induce an additional desired signal value in said field sensor from said additional field energy and an additional disturbance signal value in said field sensor from said additional interfering object to permit said signal processor to determine a substantially precise location of said field sensor to be determined despite the presence of said at least one interfering object and said additional interfering object.

12. The correction system according to clam 7, wherein said six delta coil sets include a first pair of coil elements, a second pair of coil elements, and a third pair of coil elements, said coil elements being disposed so as to be substantially mutually coplanar within a major surface of a platform.

13. The correction system according to claim 12, wherein each of said pairs of coil elements includes a long coil and a short coil, and said pairs of coils are disposed at equal angles on a circle about an axis extending substantially perpendicular to said major surface, such that for each of said pairs of coils, a radius of said circle extends perpendicular to a direction of elongation of said pair, proceeding from said long coil to said short coil.

14. The correction system according to claim 13, wherein each of said pairs of coil elements further includes at least one compensation coil, constructed and arranged to modify at least one termination point of said coil elements, so as to provide relatively a high spatial field gradient along two orthogonal axes, and substantially zero field amplitude along a third orthogonal axis.

20. A correction system for determining an effect of at least one interfering object on first and second field sensors in a navigational domain, the system comprising:

a transmitter configured to project into said navigational domain, field energy sufficient to induce a first desired signal value in said first field sensor from said transmitter and a first disturbance signal value in said first field sensor from said at least one interfering object, and to induce a second desired signal value in said second field sensor from said transmitter and a second disturbance signal value in said second field sensor from said at least one interfering object; and

,

a signal processor configured to receive said first desired and disturbance signal values and said second desired and disturbance signal values and to determine the effect of said at least one interfering object on said first field sensor from said first and second disturbance signal values, to thereby permit a substantially precise location of said first field sensor to be determined despite the presence of said at least one interfering object.

21. The correction system according to claim 20, wherein the field energy is magnetic field energy.

22. The correction system of claim 20, wherein said at least one interfering object is a ferromagnetic and electrically conductive object.

23. The correction system of claim 20, wherein said first field sensor includes an electrically conductive sensing coil.

24. The correction system according to claim 23, wherein said first field sensor includes only a single electrically conductive sensing coil.

25. The correction system of claim 24, wherein said second field sensor includes only a single electrically conductive sensing coil.

26. The correction system of claim 20, wherein said transmitter includes

(i) three unidirectional coil sets, each said unidirectional coil set being driven by a unit capable of driving said unidirectional coil set at a first sinusoidal waveform at a first frequency, and

(ii) six delta coil sets, each said delta coil set being driven by a drive unit capable of driving said delta coil set at said first sinusoidal waveform at said first frequency, such that said three unidirectional coil sets and said six delta coil sets produce said field energy at said first frequency.

27. The correction system according to claim 26, wherein said three unidirectional coil sets include a first unidirectional coil set oriented so as to produce a substantially uniform amplitude field directed in an x direction, a second unidirectional coil set oriented so as to produce substantially uniform amplitude field directed in a y direction, and a third unidirectional coil set oriented so as to produce a substantially uniform amplitude field directed in a z direction, such that said x, y and z directions are substantially mutually orthogonal.

28. The correction system according to claim 27, wherein said first unidirectional coil set having (i) a first coil pair including a first coil element and a second coil element, and (ii) a second coil pair including a third coil element and a fourth coil element, said first coil element and said third coil element being disposed in a major surface of a platform, said second coil element being disposed in a first lateral wall of said platform, and said fourth coil element being disposed in a second lateral wall of said platform, wherein said first lateral wall and said second lateral wall are substantially normal to said major surface and substantially parallel to one another.

29. The correction system according to claim 27, wherein said second unidirectional coil set having a first coil element and a second coil element disposed within a platform, said coil elements being spaced apart and substantially parallel to one another.

30. The correction system according to claim 27, wherein said third unidirectional coil set having (i) a first coil pair including a first coil element and a second coil element, and (ii) a second coil pair including a third coil element and a fourth coil element, said first coil element and said third coil element being disposed in a major surface of a platform, said second coil element being disposed in a first lateral wall of said platform, and said fourth coil element being disposed in a second lateral wall of said platform, wherein said first lateral wall and said second lateral wall are substantially normal to said major surface and substantially parallel to one another.

32. The correction system according to claim 26, wherein said six delta coil sets include a first pair of coil elements, a second pair of coil elements, and a third pair of coil elements, said coil elements being disposed so as to be substantially mutually coplanar within a major surface of a platform.

33. The correction system according to claim 32, wherein each of said pairs of coil elements includes a long coil and a short coil, and said pairs of coils are disposed at equal angles on a circle about an axis extending substantially perpendicular to said major surface, such that for each of said pairs of coils, a radius of said circle extends perpendicular to a direction of elongation of said pair, proceeding from said long coil to said short coil.

34. The correction system according to claim 33, wherein each of said pairs of coil elements further includes at least one compensation coil, constructed and arranged to modify at least one termination point of said coil elements, so as to provide relatively a high spatial field gradient along two orthogonal axes, and substantially zero field amplitude along a third orthogonal axis.

35. The correction system according to claim 26, wherein said signal processor further comprises:

(i) a first sequencer configured to sequentially activate each of three unidirectional coil sets and six delta coil sets at said first frequency, and to measure said first desired and disturbance signal values and said second desired and disturbance signal values corresponding to each of said unidirectional and delta coil sets at said first frequency; and

,

(ii) a processor configured to calculate, for each of said unidirectional and delta coil sets, an adjusted signal value as a predetermined function of said first desired and disturbance signal values and said second desired and disturbance signal values, so as to produce nine adjusted signal values, each corresponding to field energy from one of said unidirectional coil sets and said delta coil sets.

36. The correction system according to claim 20, wherein for each additional interfering object within said navigational domain, an additional field energy in an additional waveform at an additional frequency is required to induce an additional desired signal value in said field sensor from said additional field energy and an additional disturbance signal value in said field sensor from said additional interfering object to permit said signal processor to determine a substantially precise location of said field sensor to be determined despite the presence of said at least one interfering object and said additional interfering object.

37. A correction system for determining an effect of a field influencing shield device on a field sensor in a navigational domain, said correction system comprising:

a transmitter configured to project into said navigational domain field energy sufficient to induce a signal value in said field sensor;

a storage device containing information corresponding to said field energy in said navigational domain at selected locations within said navigational domain, said information including shield information incorporating the effect of said field influencing shield device at said selected locations; and

,

a processor for accessing said storage device and said signal value to determine the effect of said shield device on said field sensor, to thereby permit a substantially precise location of said field sensor to be determined despite the presence of said field influencing shield device.

31. The correction system according to claim 41, wherein said processor further comprises:

(i) first sequencer for sequentially activating each of said three unidirectional coils and said six delta coils at said first frequency, and measuring said signal value corresponding to each of said unidirectional and delta coils at said first frequency;

(ii) a data manipulating device for manipulating, for each of said unidirectional and delta coils, said storage means as a predetermined function of said shield device, so as to produce nine sets of manipulated magnetic field values, each corresponding to field energy from one of said unidirectional coils and delta coils.

38. The correction system of claim 37, wherein said field energy is magnetic field energy.

39. The correction system of claim 37, wherein said field sensor includes an electrically conductive sensing coil.

40. The correction system of claim 39, wherein said field sensor includes only a single electrically conductive sensing coil.

41. The correction system of claim 37, wherein said transmitter includes

(i) three unidirectional coil sets, each said unidirectional coil set being driven by a unit capable of driving said unidirectional coil set at a first sinusoidal waveform at a first frequency, and

(ii) six delta coil sets, each said delta coil set being driven by a drive unit capable of driving said delta coil set at said first sinusoidal waveform at said first frequency, such that said three unidirectional coil sets and said six delta coil sets produce said field energy at said first frequency.

42. The correction system according to claim 41, wherein said three unidirectional coil sets includes first unidirectional coil set oriented so as to produce a substantially uniform amplitude field directed in an x direction, a second unidirectional coil set oriented so as to produce a substantially uniform amplitude field directed in a y direction, and a third unidirectional coil set oriented so as to produce a substantially uniform amplitude field directed in a z direction, such that said x, y and z directions are substantially mutually orthogonal.

43. The correction system according to claim 42, wherein said first unidirectional coil set having (i) a first coil pair including a first coil element and a second coil element, and (ii) a second coil pair including a third coil element and a fourth coil element, said first coil element and said third coil element being disposed in a major surface of a platform, said second coil element being disposed in a first lateral wall of said platform, and said fourth coil element being disposed in a second lateral wall of said platform, wherein said first lateral wall and said second lateral wall are substantially normal to said major surface and substantially parallel to one another.

44. The correction system according to claim 42, wherein said second unidirectional coil set having a first coil element and a second coil element disposed within a platform, said coil elements being spaced apart and substantially parallel to one another.

45. The correction system according to claim 42, wherein said third unidirectional coil set having (i) a first coil pair including a first coil element and a second coil element, and (ii) a second coil pair including a third coil element and a fourth coil element, said first coil element and said third coil element being disposed in a major surface of a platform, said second coil element being disposed in a first lateral wall of said platform, and said fourth coil element being disposed in a second lateral wall of said platform, wherein said first lateral wall and said second lateral wall are substantially normal to said major surface and substantially parallel to one another.

46. The correction system according to claim 41, wherein said six delta coil sets include a first pair of coil elements, a second pair of coil elements, and a third pair of coil elements, said coil elements being disposed so as to be substantially mutually coplanar within a major surface of a platform.

47. The correction system according to claim 46, wherein each of said pairs of coil elements includes a long coil and a short coil, and said pairs of coils are disposed at equal angles on a circle about an axis extending substantially perpendicular to said major surface, such that for each of said pairs of coils, a radius of said circle extends perpendicular to a direction of elongation of said pair, proceeding from said long coil to said short coil.

48. The correction system according to claim 47, wherein each of said pairs of coil elements further includes at least one compensation coil, constructed and arranged to modify at least one termination point of said coil elements, so as to provide relatively a high spatial field gradient along two orthogonal axes, and substantially zero field amplitude along a third orthogonal axis.

49. A method of determining a substantially precise location of a field sensor within a navigational domain influenced by at least one field interfering object, the method comprising:

inducing within said field sensor a first signal value at a first waveform having a first frequency, the first signal value being influenced by said at least one field interfering object;

inducing within said field sensor a second signal value at a second waveform having a second frequency, the second signal value being influenced by said at least one field interfering object; and

,

determining an effect of said field interfering object by determining an eddy current produced in said at least one field interfering object.

50. The method according to claim 49, wherein said determining further includes calculating an adjusted signal value as a predetermined function of said first signal value and said second signal value.

51. A method of determining a substantially precise location of a first field sensor within a navigational domain influenced by at least one field interfering object, the method comprising:

inducing within said first field sensor a first signal value, the first signal value being influenced by said field interfering object;

inducing within a second field sensor a second signal value, the second signal value being influenced by said field interfering object; and

,

determining an effect of said field interfering object by determining an eddy current produced in said at least one field interfering object.

52. The method according to claim 51, wherein said determining further includes calculating an adjusted signal value as a predetermined function of said first signal value and said second signal value.

53. A method of determining a substantially precise location of a field sensor within a navigational domain influenced by a field influencing shield device, the method comprising:

inducing within said field sensor a first signal value, the first signal value being influenced by said field influencing shield device;

accessing information from a storage device, said information including shield information incorporating the effect of said field influencing shield device at selected locations; and

determining a correction to said first signal value for the effects of said field influencing shield device.

54. A method according to claim 53, wherein said determining a correction further including manipulating said storage device as a predetermined function of said shield information, so as to produce a set of manipulated magnetic field values corresponding to said effects of said field influencing shield device.

55. A method of determining a substantially precise location of a field sensor within a navigational domain influenced by a field interfering object, the method comprising:

sequentially projecting into said navigational domain, via three unidirectional coils and six delta coils, navigational energy at a first frequency, and measuring a first signal value in said field sensor corresponding to each of said three unidirectional coils and said six delta coils, so as to produce nine of said first signal values;

sequentially projecting into said navigational domain, via three unidirectional coils and six delta coils, and said navigational energy at a second frequency, and measuring a second signal value in said field sensor corresponding to each of said three unidirectional coils and said six delta coils, so as to produce nine of said second signal values;

calculating, for each of said unidirectional and delta coils, an adjusted signal value as a predetermined function of said first signal value and said second signal value, so as to produce nine adjusted signal values, each corresponding to navigational magnetic energy from one of said unidirectional coils and delta coils;

forming three independent equations including (i) three adjusted signal values corresponding to said unidirectional coils, (ii) three predetermined field magnitude values due to each of said unidirectional coils and corresponding to said navigational energy at a last navigational point of said field sensor, and (iii) unknown orientation variables, and simultaneously solving said independent equations to determine said orientation variables corresponding to said compensated orientation of said field sensor;

generating three lines and determining an intersection of said three lines, said intersection corresponding to said compensated position of said field sensor, wherein each of said lines is generated from (i) adjusted signal values corresponding to a pair of said delta coils, and (ii) predetermined field magnitude values due to said pair of delta coils and corresponding to said navigational energy at said last navigational point of said field sensor while oriented according to said compensated orientation.

56. A method of determining a substantially precise location of a first field sensor within a navigational domain influenced by a field interfering object, the method comprising:

sequentially projecting into said navigational domain, via three unidirectional coils and six delta coils, a navigational energy at a first frequency, measuring a first signal value in said first field sensor corresponding to each of said three unidirectional coils and said six delta coils, so as to produce nine of said first signal values, and measuring a second signal value in a second field sensor corresponding to each of said three unidirectional coils and said six delta coils, so as to produce nine of said second signal values;

calculating, for each of said unidirectional and delta coils, an adjusted signal value as a predetermined function of said first signal value and said second signal value, so as to produce nine adjusted signal values, each corresponding to navigational magnetic energy from one of said unidirectional coils and delta coils;

forming three independent equations including (i) three adjusted signal values corresponding to said unidirectional coils, (ii) three predetermined field magnitude values due to each of said unidirectional coils and corresponding to said navigational energy at a last navigational point of said first field sensor, and (iii) unknown orientation variables, and simultaneously solving said independent equations to determine said orientation variables corresponding to said compensated orientation of said first field sensor;

generating three lines and determining an intersection of said three lines, said intersection corresponding to said compensated position of said first field sensor, wherein each of said lines is generated from (i) adjusted signal values corresponding to a pair of said delta coils, and (ii) predetermined field magnitude values due to said pair of delta coils and corresponding to said navigational energy at said last navigational point of said first field sensor while oriented according to said compensated orientation.

57. A method of determining a substantially precise location of a first field sensor within a navigational domain influenced by a field influencing shield device, the method comprising:

sequentially projecting into said navigational domain, via three unidirectional coils and six delta coils, a navigational energy at a first frequency, measuring a first signal value in said field sensor corresponding to each of said three unidirectional coils and said six delta coils, so as to produce nine of said first signal values;

forming three independent equations including (i) three adjusted signal values corresponding to said unidirectional coils, (ii) three predetermined field magnitude values due to fields from each of said unidirectional coils and corresponding to said navigational energy at a last navigational point of said field sensor, said predetermined field magnitude values being manipulated so as to account for said shield device, and (iii) unknown orientation variables, and simultaneously solving said independent equations to determine said orientation variables corresponding to said compensated orientation of said sensing coil;

generating three lines and determining an intersection of said three lines, said intersection corresponding to said compensated position of said sensing coil, wherein each of said lines is generated from (i) adjusted signal values corresponding to a pair of said delta coils, and (ii) predetermined field magnitude values due to said pair of delta coils and corresponding to said navigational energy at said last navigational point of said sensing coil while oriented according to said compensated orientation, said predetermined field magnitude values being manipulated so as to account for said effect of the shield device.