Variable magnetic moment MR navigation

• US 20050043611A1
• Filed: 04/29/2004
• Published: 02/24/2005
• Est. Priority Date: 05/02/2003
• Status: Active Grant

• Current Assignee: Stereotaxis, Inc.
• Original Assignee: Stereotaxis, Inc.
• Inventors: Ritter, Rogers C., Viswanathan, Raju R., Hastings, Roger N., Sabo, Michael E.
• Granted Patent: US 7,389,778 B2
• Time in Patent Office: Days
• US Class Current: 600/411
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• 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

Abstract

A method of navigating a medical device in an operating region in a subject. The method includes applying a magnetic field to the operating region and changing the magnetic moment of the medical device by selectively changing a physical condition of at least one magnet element in the medical device to change the orientation of the device with respect to the applied magnetic field.

Claims

1. A method of navigating a medical device in an operating region in a subject, the method comprising:

applying a magnetic field to the operating region;

changing the magnetic moment of the medical device by selectively changing a physical condition of at least one magnet element in the medical device to change the orientation of the device with respect to the applied magnetic field.

2. The method according to claim 1 wherein the magnetic field is applied with at least one external source magnet.

3. The method according to claim 1 wherein the magnetic field is applied with a magnetic resonance imaging system.

4. The method according to claim 1 wherein the step of changing a physical condition of at least one magnet element comprises heating the at least one magnet element.

5. The method according to claim 4 wherein the step of changing a physical condition of at least one magnet element comprises allowing a heated magnet element to cool through transfer of heat to the operating region.

6. The method according to claim 1 wherein the step of changing a physical condition of at least one magnet element comprises cooling the at least one element.

7. The method according to claim 6 wherein the step of changing a physical condition of at least one magnetic element comprises allowing a cooled element to warm through transfer of heat from the operating region.

8. The method according to claim 1 wherein the step of heating the at least one magnetic element comprises applying electric current to at least one conducting lead extending to a heating element.

9. The method according to claim 1 wherein the step of cooling the at least one magnetic element comprises applying electric current to a cooling element.

10. The method according to claim 9 wherein the cooling element is a Peltier effect element.

11. The method according to claim 1 wherein the step of heating the at least one magnetic element comprises conducting laser energy via an optical fiber to the magnetic element.

12. The method according to claim 1 wherein the step of heating the at least one magnetic element comprises conducting laser energy to the magnetic element via an optical fiber.

13. The method according to claim 1 wherein the step of heating the at least one magnetic element comprises conducting optical energy to a photovoltaic cell adjacent the magnetic elements, and using the electrical power to heat the magnet element.

14. A method of navigating a medical device in an operating region in a subject to which an externally generated magnetic field is applied, the method comprising changing the magnetic moment of the medical device by changing a physical condition of at least one magnet element.

15. The method according to claim 14 wherein the magnetic field is applied to the operating region with an external source magnet.

16. The method according to claim 14 wherein the magnetic field is applied to the operating region with a magnetic resonance imaging system.

17. The method according to claim 14 wherein changing the physical condition of the at least one magnet element comprises heating the at least one magnet element.

18. The method according to claim 14 wherein changing the physical condition of the at least one magnet element comprises cooling the at least one magnet element.

19. The method according to claim 14 wherein changing the physical condition of the at least one magnet element comprises applying light to the at least one magnet element.

20. The method according to claim 14 wherein changing the physical condition of the at least one magnet element comprises applying mechanical force to the at least one magnet element sufficient to change its magnetic properties.

21. A method of navigating a medical device in an operating region in a subject using an externally applied magnetic field, the method comprising:

changing the magnetic moment at a point on the medical device by changing the temperature of at least one magnetic element.

22. The method according to claim 21 wherein the step of changing the temperature of at least one magnetic element comprises the step of selectively changing the temperature of at least one of a plurality of magnet elements in the medical device to change the magnetic moment at a point on the medical device.

23. The method according to claim 21 wherein the step of changing the temperature of at least one magnetic element includes heating the element to a temperature above the Curie temperature of the material comprising the element.

24. The method according to claim 21 wherein the step of changing the temperature of at least one magnetic element includes cooling the element to a temperature below the Curie temperature of the material comprising the element.

25. The method according to claim 21 wherein the step of changing the temperature of at least one magnetic element comprises heating the material with light.

26. The method according to claim 21 wherein the step of changing the temperature of at least one magnetic element comprises resistance heating the material.

27. The method according to claim 21 wherein the step of changing the temperature of at least one magnetic element comprises circulating a heated fluid adjacent the element.

28. The method according to claim 21 wherein the step of changing the temperature of at least one magnetic element comprises circulating a cooled fluid adjacent the element.

29. The method according to claim 21 wherein the step of changing the temperature comprise allowing heat to dissipate from the element.

44. The method of claim 23 where electronic multiplexing is used to distribute electrical current to the elements for resistance heating.

46. The method of claim 25 wherein a plurality of optical fibers is used to distribute light energy used for effecting temperature change.

47. The method of claim 46, where the distribution of light energy across the optical fibers is computer-controlled.

48. The method of claim 47, where the distribution of light energy is controlled with the use of device location information, obtained through suitable imaging means, in such a manner as to steer the device towards a desired anatomical target.

49. The method of claim 48, where the light intensities controlling the temperature of each magnet element are controlled with the use of device material properties and a physics model of three dimensional deformations in such a manner as to steer the device towards a desired anatomical target.

30. A method of navigating a medical device in an operating region in a subject using an externally applied magnetic field, the method comprising:

changing the magnetic moment at a point on the medical device by changing the temperature of at least of a plurality of elongate magnetic elements.

31. A method of navigating a medical device in an operating region in a subject using an externally applied magnetic field, the method comprising:

changing the magnetic moment at a point on the medical device by raising the temperature of at least one of a plurality of elongate magnetic elements above the Curie point temperature of the material.

32. A method of navigating a medical device in an operating region in a subject using an externally applied magnetic field, the method comprising:

changing the magnetic moment at a point on the medical device by lowering the temperature of at least one of a plurality of elongate magnetic elements below the Curie point temperature of the material.

33. A medical device navigable in an operating region in a subject using an externally applied magnetic field, the device including at least one element of a material whose magnetization can be altered by changing a physical condition of the material.

34. The medical device according to claim 33 further comprising means for changing the physical condition of the material.

50. The method claim 33 further comprising advancing and retracting the medical device with an advancer mechanism.

51. The method of claim 50 wherein the advancer mechanism is under computer control.

35. A medical device navigable in an operating region in a subject using an externally applied magnetic field, the device including at least one element of a thermomagnetic material whose magnetization can be altered by a temperature change that is between 0°

C. and 200°

C.

36. The medical device according to claim 35 wherein the magnetization of the thermomagnetic material can be altered by a temperature change that is within 100°

of body temperature.

37. The medical device according to claim 35 wherein the device includes an optomagnetic material whose magnetization can be altered by the application of light.

38. The medical device according to claim 35 wherein the device includes an piezomagnetic material whose magnetization can be altered by the application of pressure.

39. The medical device according to claim 35 wherein device includes an electri-magnetic element whose magnetization direction can be altered by the application of an electric field

40. The medical device according to claim 35 wherein the device includes an piezomagnetic element whose magnetization direction can be altered by the application of mechanical stress.

41. The medical device according to claim 35 wherein the thermomagnetic material has a Curie temperature above normal body temperature, and further comprising means for selectively heating the at least one elements above the Curie temperature.

42. The medical device according to claim 35 wherein the thermomagnetic material has a Curie temperature below normal body temperature, and further comprising means for selectively cooling the at least one element below its Curie temperature.

43. The medical device according to claim 35 wherein the plurality of elements are arranged in at least skewed, divergent cylindrical array.

45. The method of claim 43 wherein the distribution of current is computer-controlled.

52. A medical device for navigation in an operating region in a subject to which a magnetic field is applied, the device comprising means for changing the magnetic moment at the distal end of the device.

53. A medical device for navigating in an operating region in a subject to which a magnetic field is applied, the device comprising at least one magnet element, and means for selectively changing a physical property of the at least one magnet element to change the magnetic moment of the device.

54. The device according to claim 53 wherein in the means for selectively changing the physical property of the at least one magnet element comprises means for heating the at least one magnet element.

55. The device according to claim 53 wherein in the means for selectively changing the physical property of the at least one magnet element comprises means for cooling the at least one magnet element.