Object tracking using a single sensor or a pair of sensors

• US 20020062203A1
• Filed: 03/29/2001
• Published: 05/23/2002
• Est. Priority Date: 03/09/2000
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Super Dimension Ltd.
• Inventors: Gilboa, Pinhas
• Granted Patent: US 6,615,155 B2
• Time in Patent Office: Days
• US Class Current: 702/150
• CPC Class Codes: A61B 5/06 Devices, other than using radiation, for detecting or locating foreign bodies for removing same A61B17/50 ; determining position of probes within or on the body of the patient
• CPC Class Codes: A61B 5/062 using magnetic field
• CPC Class Codes: G01D 5/2073 by movement of a single coil with respect to two or more coils
• CPC Class Codes: G01D 5/2086 by movement of two or more coils with respect to two or more other coils

Abstract

A method and system for tracking a moving object. The object is provided with one or more single-component sensors of a vector field. Generators of the vector field also are provided. Parameters of equations that relate the generated fields, as measured by the sensors, to the position of the object, but not to the orientation of the object, are determined either empirically or theoretically. These equations are solved to determine the position of the object without having to determine the orientation of the object. The scope of the invention also includes a helical guide wire wherein are integrally included one or more single-component sensors of a quasistatic magnetic field.

Claims

1. A method of tracking an object that moves in three dimensions, comprising the steps of:

(a) providing the object with at least one vector field component sensor for measuring a respective component of a vector field;

(b) for each said at least one vector field component sensor, empirically determining parameters of a set of equations that relate said respective component only to a position of the object with respect to a reference frame;

(c) providing a plurality of vector field generators for generating respective instances of said vector field, each said generator having a fixed respective position in said reference frame;

(d) for each said generator;

(i) generating said respective instance of said vector field, and

(ii) for each said at least one sensor, measuring said respective component of said respective instance of said vector field; and

(e) solving said set of equations for said position of the object.

2. The method of claim 1, wherein said vector field is a magnetic field.

3. The method of claim 2, wherein each said at least one sensor includes at least one loop of an electrical conductor.

4. The method of claim 2, wherein each said at least one sensor includes a single-component magnetometer.

5. The method of claim 2, wherein each said generator includes a radiator of said respective instance of said vector field, each said radiator including at least one loop of an electrical conductor.

6. The method of claim 1, wherein said generators are mutually independent.

7. The method of claim 1, wherein each said generator includes a radiator of said respective instance of said vector field, at least one of said radiators being spatially extended.

8. The method of claim 1, wherein the object is provided with at most two said sensors.

9. The method of claim 8, wherein at least three said vector field generators are provided.

10. The method of claim 8, wherein the object is provided with exactly one said sensor.

11. The method of claim 10, wherein at least five said vector field generators are provided, and wherein said generating of said instances of said vector fields includes generating three independent groups of said instances, each said group including three said instances.

12. The method of claim 1, wherein said equations are polynomials in coordinates of said position of the object, said parameters of said equations being coefficients of said polynomials.

13. The method of claim 1, further comprising the step of:

(f) computing an orientation of the object with respect to said reference frame.

15. The method of claim 14, wherein said vector field is a magnetic field.

16. The method of claim 15, wherein each said sensor includes at least one loop of an electrical conductor.

17. The method of claim 15, wherein each said sensor includes a single- component magnetometer.

18. The method of claim 15, wherein each said generator includes a radiator of said respective instance of said vector field, each said radiator including at least one loop of an electrical conductor.

19. The method of claim 14, wherein said generators are mutually independent.

20. The method of claim 14, wherein each said generator includes a radiator of said respective instance of said vector field, at least one of said radiators being spatially extended.

21. The method of claim 14, wherein the object is provided with exactly one said sensor.

22. The method of claim 21, wherein at least five said vector field generators are provided, and wherein said generating of said instances of said vector fields includes generating three independent groups of said instances, each said group including three said instances.

23. The method of claim 14, wherein said parameters are determined empirically.

24. The method of claim 14, wherein said parameters are determined theoretically.

25. The method of claim 14, wherein said equations are polynomials in coordinates of said position of the object, said parameters of said equations being coefficients of said polynomials.

26. The method of claim 14, further comprising the step of:

(f) computing an orientation of the object with respect to said reference frame.

28. The system of claim 27, including a single said vector field component sensor.

29. The system of claim 28, wherein said single vector field component is included in a distal portion of a guide wire.

30. The system of claim 27, including exactly two said vector field component sensors.

31. The system of claim 30, wherein said two vector field component sensors are in tandem in a distal portion of a guide wire.

32. The system of claim 30, wherein said two vector field component sensors are included in a distal portion of a guide wire, with a first said vector field component sensor being substantially parallel to a longitudinal axis of said guide wire and a second said vector field component sensor being substantially perpendicular to said axis.

14. A method of tracking an object that moves in three dimensions, comprising the steps of:

(a) providing the object with at most two vector field component sensors for measuring respective components of a vector field;

(b) for each said at most two vector field component sensors, determining parameters of a set of equations that relate said respective component only to a position of the object with respect to a reference frame;

(c) providing at least three vector field generators for generating respective instances of said vector field, each said generator having a fixed respective position in said reference frame;

(d) for each said generator;

(i) generating said respective instance of said vector field, and

(ii) for each said at most two sensors, measuring said respective component of said respective instance of said vector field; and

(e) solving said set of equations for said position of the object.

27. A system for tracking an object that moves in three dimensions, comprising:

(a) at least one vector field component sensor, associated with the object, for measuring a respective component of a vector field;

(b) a processor for solving a set of equations that relate, for each said at least one sensor, said respective component of said vector field only to a position of the object with respect to a reference frame;

(c) a memory for storing empirically determined parameters of said equations; and

(d) a plurality of vector field generators, having fixed respective positions in said reference frame, for generating respective instances of said vector field.

33. A system for tracking an object that moves in three dimensions, comprising:

(a) at most two vector field component sensors, associated with the object, for measuring respective components of a vector field;

(b) a processor for solving a set of equations that relate, for each said sensor, said respective component of said vector field only to a position of the object with respect to a reference frame;

(c) a memory for storing parameters of said equations; and

(d) at least three vector field generators, having fixed respective positions in said reference frame, for generating respective instances of said vector field.

34. The system of claim 33, including a single said vector field component sensor.

35. The system of claim 34, wherein said single vector field component is included in a distal portion of a guide wire.

36. The system of claim 33, including exactly two said vector field component sensors.

37. The system of claim 36, wherein said two vector field component sensors are in tandem in a distal portion of a guide wire.

38. The system of claim 36, wherein said two vector field component sensors are included in a distal portion of a guide wire, with a first said vector field component sensor being substantially parallel to a longitudinal axis of said guide wire and a second said vector field component sensor being substantially perpendicular to said axis.

40. The guide wire of claim 39, wherein said distal portion includes a plurality of said electrically conducting sections, each pair of successive said electrically conducting sections having therebetween an electrically insulating section in tandem with said each pair of successive electrically conducting sections.

41. The guide wire of claim 39, further comprising:

(c) a substantially helical, electrically conducting proximal portion in tandem with said medial portion.

42. The guide wire of claim 39, further comprising:

(c) a first electrically conducting wire, electrically coupled to a distal end of said distal portion; and

(d) a second electrically conducting wire, electrically coupled to a proximal end of said distal portion.

43. The guide wire of claim 42, wherein said distal and medial portions define an axial channel, wherethrough said electrically conducting wires extend substantially parallel to said axis.

39. A guide wire, comprising:

(a) a substantially helical distal portion including at least one electrically conducting section; and

(b) a substantially helical, electrically insulating medial portion in tandem with said distal portion.

44. A method of tracking an object that moves in three dimensions, comprising the steps of:

(a) providing the object with at least one vector field component sensor for measuring a respective component of a vector field;

(b) empirically determining a rotationally invariant operator that relates said at least one respective component to a position of the object with respect to a reference frame;

(c) providing a plurality of vector field generators for generating respective instances of said vector field, each said generator having a fixed respective position in said reference frame;

(d) for each said generator;

(i) generating said respective instance of said vector field, and

(ii) for each said at least one sensor, measuring said respective component of said respective instance of said vector field; and

(e) computing said position of the object, using said operator.

45. A method of tracking an object that moves in three dimensions, comprising the steps of:

(a) providing the object with at most two vector field component sensors for measuring respective components of a vector field;

(b) determining a rotationally invariant operator that relates said at most two respective components to a position of the object with respect to a reference frame;

(c) providing at least three vector field generators for generating respective instances of said vector field, each said generator having a fixed respective position in said reference frame;

(d) for each said generator;

(i) generating said respective instance of said vector field, and

(ii) for each said at most two sensors, measuring said respective component of said respective instance of said vector field; and

(e) computing said position of the object, using said operator.

46. A system for tracking an object that moves in three dimensions, comprising:

(a) at least one vector field component sensor, associated with the object, for measuring a respective component of a vector field;

(b) a memory for storing an empirically determined, rotationally invariant operator that relates said at least one respective component of said vector field to a position of the object with respect to a reference frame;

(c) a processor for computing said position, using said operator; and

(d) a plurality of vector field generators, having fixed respective positions in said reference frame, for generating respective instances of said vector field.

47. A system for tracking an object that moves in three dimensions, comprising:

(a) at most two vector field component sensors, associated with the object, for measuring respective components of a vector field;

(b) a memory for storing a rotationally invariant operator that relates said at most two respective components of said vector field to a position of the object with respect to a reference frame;

(c) a processor for computing said position, using said operator; and

(d) at least three vector field generators, having fixed respective positions in said reference frame, for generating respective instances of said vector field.

48. A method of tracking an object that moves in three dimensions, comprising the steps of:

(a) providing the object with at most two vector field component sensors for measuring respective components of a vector field;

(b) for each said at most two vector field component sensors, determining parameters of a set of equations that relate said respective component to a position of the object with respect to a reference frame, independent of an orientation of the object;

(c) providing at least three vector field generators for generating respective instances of said vector field, each said generator having a fixed respective position in said reference frame;

(d) for each said generator;

(i) generating said respective instance of said vector field, and

(ii) for each said at most two sensors, measuring said respective component of said respective instance of said vector field; and

(e) solving said set of equations for said position of the object.

49. A system for tracking an object that moves in three dimensions, comprising:

(a) at most two vector field component sensors, associated with the object, for measuring respective components of a vector field;

(b) a processor for solving a set of equations that relate, for each said sensor, said respective component of said vector field to a position of the object with respect to a reference frame, independent of an orientation of the object;

(c) a memory for storing parameters of said equations; and

(d) at least three vector field generators, having fixed respective positions in said reference frame, for generating respective instances of said vector field.