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

• US 7,797,032 B2
• Filed: 09/23/2002
• Issued: 09/14/2010
• Est. Priority Date: 10/28/1999
• Status: Active Grant

• Current Assignee: Surgical Navigation Technologies, Inc. (Medtronic Plc)
• Original Assignee: Medtronic Navigation Incorporated (Medtronic Plc)
• Inventors: Martinelli, Michael A., Jascob, Brad, Kessman, Paul
• Primary Examiner(s): Casler; Brian
• Assistant Examiner(s): KISH, JAMES M
• Application Number:
  US10/252,258
• Publication Number:
  US 20030117135A1
• Time in Patent Office: 2,913 Days
• Field of Search: 600407-482, 128/899, 324244-247, 324/301, 324/302, 324256-259
• 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 system includes a first and second transmitter to create signals. A signal processor is able to process the created signals. The method can include determining interference and/or a correct signal based on the two signals. Also, a shield can be provided to limit transmission of selected fields.

Claims

1. A system for navigating a probe in the presence of a field-influencing object, said system comprising:

a sensing coil fixed to the probe operable to be navigated;

a tool coil operably connected to a tool;

a transmitter operable to radiate field energy sufficient to induce a signal in said sensor, wherein said transmitter includes;

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

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

a shield operable to reflect said field energy; and

a processor operable to determine a location of said sensor based upon said signal induced in said sensor;

wherein said shield is placed between said transmitter and the field influencing object to block affects of the field influencing object on the field energy;

wherein said tool is a second field-influencing object and said field energy induces a first signal in said sensing coil and a second signal in said tool coil simultaneously;

wherein said processor is operable, using said first and second signals, to isolate an affect of the tool on said sensing coil by subtracting a voltage induced in the sensing coil by the tool.

2. The system as defined in claim 1 further comprising a storage device containing information corresponding to said field energy at selected locations, said information including shield information incorporating an effect of said shield at said selected locations.

3. The system as defined in claim 2 wherein said processor is further operable to access said storage device to determine an effect of said shield on said sensor, to thereby permit a substantially precise location of said sensor to be determined despite the presence of the field influencing object.

4. The system as defined in claim 2 wherein said storage device containing said shield information includes a geometry of said shield.

5. The system as defined in claim 1 wherein the sensor is connected to a probe that is selected from a group comprising a flexible catheter, a rigid catheter, a surgical tool, a drill, and a reamer.

6. The system as defined in claim 1 wherein said sensor is fixedly connected to a distal end of a catheter insertable into a selected body cavity of a patient undergoing a surgical procedure.

7. The system as defined in claim 1 wherein said field energy is electro-magnetic field energy.

8. The system as defined in claim 1 wherein said shield is formed of a conductive material.

9. The system as defined in claim 8 wherein said conductive material is selected from a group comprising aluminum, copper, and a polymer film with a conductive coating.

10. The system as defined in claim 1 wherein said shield is formed as a conductive sheet.

11. The system as defined in claim 1 wherein said shield is formed as a conductive mesh.

12. The system as defined in claim 1 wherein said shield is formed from strips of conductive material.

13. The system as defined in claim 1 wherein said shield is fixed relative to said transmitter.

14. The system as defined in claim 13, wherein the shield is a distance from said transmitter.

15. The system as defined in claim 1 wherein said determinable location of said sensor by said processor includes angular orientation and positional coordinates of said sensor.

16. The system of claim 1 wherein said shield is a geometrically shaped thin member positioned adjacent to a navigational domain defined by the transmitter;

wherein the shield cancels the effects of the field influencing object positioned beyond the navigational domain.

17. The system as defined in claim 1, wherein the field influencing object is selected from a group comprising an operating table, a microscope, a C-arm, and an instrument having a ferromagnetic and conducting core.

18. A method for navigating a probe in the presence of a field-influencing object, said system comprising:

radiating field energy sufficient to induce a signal in a sensor;

reducing propagation of said field energy through a shield;

storing information values in a look-up-table (LUT) corresponding to said field energy at selected locations wherein the values in the LUT are adjusted with voltage adjustment values incorporating an effect of said shield at said selected locations;

accessing said stored information by a processor; and

determining a location of said sensor be executing instructions with said processor based upon said signal induced in said sensor and said accessed stored information despite the presence of the field influencing object;

wherein said field energy is radiated with,

(i) three unidirectional coil sets, each of said unidirectional coil sets driven by a drive unit capable of driving said unidirectional coil sets at a first sinusoidal wave form at a first frequency, and

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

19. The method as defined in claim 18 further comprising manipulating, for each of the unidirectional and delta coils, values in the LUT stored in the storage device to generate the adjusted values as a predetermined function of said shield, so as to produce nine (9) sets of manipulated magnetic field values as the adjusted values, each corresponding to navigational magnetic energy from one of the unidirectional coils and delta coils.

20. The method as defined in claim 18 wherein the sensor is connected to a probe that is selected from a group comprising a flexible catheter, a rigid catheter, a surgical tool, a drill, and a reamer.

21. The method as defined in claim 18 wherein said sensor is fixedly connected to a distal end of a catheter insertable into a selected body cavity of a patient undergoing a surgical procedure.

22. The method as defined in claim 18 wherein said field energy is electro-magnetic field energy.

23. The method as defined in claim 18 wherein said shield is formed of a conductive material.

24. The method as defined in claim 18 wherein said conductive material is selected from a group comprising aluminum, copper, and a polymer film with a conductive coating.

25. The method as defined in claim 18 wherein said shield is formed as a conductive sheet.

26. The method as defined in claim 18 wherein said shield is formed as a conductive mesh.

27. The method as defined in claim 18 wherein said shield is formed from strips of conductive material.

28. The method as defined in claim 18, wherein the shield is a distance from said transmitter and operable to reflect said field energy radiated from said transmitter.

29. A method for navigating a sensor within a navigational domain in the presence of a field influencing object, said method comprising:

generating a field operable to induce a signal in a sensor with a transmitter, wherein the transmitter includes;

(i) driving each of three unidirectional coil sets at a first sinusoidal wave form at a first frequency, and

(ii) driving each of six delta coil sets at said first sinusoidal wave form at said first frequency, such that said three unidirectional coil sets and said six delta coil sets produce field energy at said first frequency;

reflecting the field with a shield that separates a field influencing object from both the transmitter and the sensor, thus forming a reflected field with the shield separate from the field generated with the transmitter;

inducing a first signal within the sensor from the produced field energy;

inducing a second signal within the sensor from the reflected field energy; and

determining a location of the sensor at least in part using the first signal and the second signal induced in the sensor with a processor configured to calculate, for each of the unidirectional and delta coil sets, an adjusted signal value as a predetermined function of the first signal and the second signal, so as to produce nine adjusted signal values, each corresponding to field energy from one of the unidirectional coil sets and the delta coil sets.

30. The method of claim 29, further comprising actuating the transmitter to radiate field energy.

31. A system for navigating a probe in the presence of a field-influencing object, said system comprising:

a first sensor;

a transmitter operable to radiate transmitter field energy sufficient to induce a first signal in said first sensor, wherein said transmitter includes;

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

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

a shield positioned between said transmitter and the field-influencing object to reflect said transmitter field energy to substantially cancel effects of the field-influencing object; and

a processor operable to determine a location of said first sensor based upon said first signal induced in said first sensor by calculating for each of the unidirectional and delta coil sets a signal value corresponding to field energy from each of the unidirectional coil sets and the delta coil sets as a part of the first signal;

wherein said shield is placed between said transmitter and the field-influencing object to block affects of the field-influencing object on said transmitter field energy.

32. The system of claim 31, further comprising:

a storage device containing information corresponding to said transmitter field energy and a reflected field energy at selected locations;

wherein said information includes shield information incorporating an effect of said shield at said selected locations;

wherein said effect of said shield includes said reflected field reflected from the shield that is separate from said transmitter field energy generated with the transmitter;

wherein said processor, in determining the location of the first sensor, is further operable to use a second signal induced in the first sensor based upon said reflected field and for each of the unidirectional and delta coil sets, an adjusted signal value as a predetermined function of the first signal and the second signal, so as to produce nine adjusted signal values, each corresponding to field energy from one of the unidirectional coil sets and the delta coil sets.

33. The system as defined in claim 32 wherein the sensor is connected to a probe operable to be navigated in a human body, wherein the probe is selected from a group comprising a flexible catheter, a rigid catheter, a surgical tool, a drill, and a reamer.

34. The system of claim 33, further comprising:

a second sensor affixed to the field-influencing object and the transmitter inducing in said second sensor a third signal in said second sensor;

wherein the processor is operable to receive said third signal from said second sensor on said field-influencing object;

wherein said processor is operable to access the information in the storage device regarding the transmitter field energy and the reflected field energy;

wherein the processor is operable to determine the location of the first sensor based on all of the third signal and the information stored in the storage device.

35. The system as defined in claim 31 wherein said sensor is fixedly connected to a distal end of a catheter insertable into a selected body cavity of a patient undergoing a surgical procedure.

36. The system as defined in claim 31 wherein said field energy is electro-magnetic field energy.

37. The system as defined in claim 31 wherein said shield is formed of a conductive material.

38. The system as defined in claim 37 wherein said conductive material is selected from a group comprising aluminum, copper, and a polymer film with a conductive coating.

39. The system as defined in claim 31 wherein said shield is formed as a conductive sheet.

40. The system as defined in claim 31 wherein said shield is formed as a conductive mesh.

41. The system as defined in claim 31 wherein said shield is formed from strips of conductive material.

42. The system as defined in claim 31 wherein said shield is a geometrically shaped thin member positioned adjacent to a navigational domain defined by the transmitter;

wherein the shield cancels the effects of the field influencing object positioned beyond the navigational domain.

43. The system as defined in claim 31 wherein the six delta coil sets include a long coil set and a short coil set,

wherein each of the six delta coil sets is positioned about 120 degrees apart around a point.