SWITCHED DIVERTER CIRCUITS FOR MINIMIZING HEATING OF AN IMPLANTED LEAD IN A HIGH POWER ELECTROMAGNETIC FIELD ENVIRONMENT

• US 20100168821A1
• Filed: 01/12/2010
• Published: 07/01/2010
• Est. Priority Date: 04/13/2001
• Status: Active Grant

• Current Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Original Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Inventors: Dabney, Warren S., Stevenson, Robert A., Lardo, Albert C., Moschiano, Holly Noelle, Brainard, Scott, Johnson, Robert Shawn, Halperin, Henry R., Kaiser, Daniel Robert, Williams, Christopher Michael
• Granted Patent: US 8,509,913 B2
• Time in Patent Office: Days
• US Class Current: 607/63
• CPC Class Codes: A61B 18/02 by cooling, e.g. cryogenic techniques devices for cooling specific reflex points of the body within cell-life limits A61H39/06
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• CPC Class Codes: A61B 2018/00839 Bioelectrical parameters, e.g. ECG, EEG
• CPC Class Codes: A61B 2018/1293 having means to prevent interference
• CPC Class Codes: A61B 2018/147 Electrodes transferring energy by capacitive coupling, i.e. with a dielectricum between electrode and target tissue
• CPC Class Codes: A61B 2090/374 NMR or MRI
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61N 1/086 Magnetic resonance imaging [MRI] compatible leads
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents
• CPC Class Codes: G01R 33/285 Invasive instruments, e.g. catheters or biopsy needles, specially adapted for tracking, guiding or visualization by NMR
• CPC Class Codes: G01R 33/286 involving passive visualization of interventional instruments, i.e. making the instrument visible as part of the normal MR process

Abstract

An energy management system that facilitates the transfer of high frequency energy induced on an implanted lead or a leadwire includes an energy dissipating surface associated with the implanted lead or the leadwire, a diversion or diverter circuit associated with the energy dissipating surface, and at least one switch for diverting energy in the implanted lead or the leadwire through the diversion circuit to the energy dissipating surface. In alternate configurations, the switch may be disposed between the implanted lead or the leadwire and the diversion circuit, or disposed so that it electrically opens the implanted lead or the leadwire when diverting energy through the diversion circuit to the energy dissipating surface. The switch may comprise a single or multi-pole double or single throw switch. The diversion circuit may be either a high pass filter or a low pass filter.

Claims

1. A switched diverter circuit for minimizing heating of an implanted lead and/or providing EMI protection in a high power electromagnetic field environment, comprising:

an implanted lead or a leadwire;

an energy dissipating surface associated with the implanted lead or the leadwire;

a diversion circuit associated with the energy dissipating surface; and

at least one switch for diverting energy in the implanted lead or the leadwire through the diversion circuit to the energy dissipating surface.

2. The switched diverter circuit of claim 1, wherein the switch electrically opens the implanted lead or the leadwire when diverting energy in the implanted lead or the leadwire through the diversion circuit to the energy dissipating surface.

3. The switched diverter circuit of claim 2, wherein the switch comprises a single or multi-pole double throw switch.

4. The switched diverter circuit of claim 1, wherein the switch is disposed between the implanted lead or the leadwire and the diversion circuit.

5. The switched diverter circuit of claim 1, wherein the switch is disposed between the diversion circuit and the energy dissipating surface.

6. The switched diverter circuit of claim 4 or 5, wherein the switch comprises a single or multi-pole single throw switch.

7. The switched diverter circuit of claim 4 or 5, wherein the switch comprises a MEMS switch, a mechanical switch, a reed switch, an electronic switch, a programmable switch, an automatically actuated switch, a Hall Effect switch, or a field effect transistor (FET) switch.

8. The switched diverter circuit of claim 1, wherein the implanted lead or the leadwire has impedance characteristics at a selected RF frequency or frequency band, and wherein the diversion circuit has impedance characteristics at least partially tuned to the implanted lead'"'"'s or the leadwire'"'"'s impedance characteristics.

9. The switched diverter circuit of claim 8, wherein the selected RF frequency or frequency band comprises an MRI frequency.

10. The switched diverter circuit of claim 9, wherein said MRI frequency comprises a range of MRI frequencies.

11. The switched diverter circuit of claim 8, wherein the diversion circuit has a reactance and is vectorially opposite to the characteristic reactance of the implanted lead.

12. The switched diverter circuit of claim 11, wherein the diversion circuit has a capacitive reactance generally equal and opposite to the characteristic inductive reactance of the implanted lead.

13. The switched diverter circuit of claim 8, wherein the capacitive reactance and the inductive reactance each have a resistor component.

14. The switched diverter circuit of claim 1 or 8, wherein the diversion circuit comprises a low pass filter.

15. The switched diverter circuit of claim 14, wherein the low pass filter comprises a capacitor, an inductor, a Pi filter, a T filter, an LL filter, or an “

n”

element filter.

16. The switched diverter circuit of claim 1 or 8, wherein the diversion circuit comprises at least one series resonant LC trap filter.

17. The switched diverter circuit of claim 16, wherein the diversion circuit comprises a plurality of L-C trap filters resonant respectively at different MRI frequencies.

18. The switched diverter circuit of claim 1, wherein the energy dissipating surface comprises a housing for an active implantable medical device (AIMD).

19. The switched diverter circuit of claim 18, wherein the AIMD comprises an implantable hearing device, a neurostimulator, a brain stimulator, a cardiac pacemaker, a left ventricular assist device, an artificial heart, a drug pump, a bone growth stimulator, a urinary incontinence device, a spinal cord stimulator, an anti-tremor stimulator, an implantable cardioverter defibrillator, a congestive heart failure device, or a cardio resynchronization therapy device.

20. The switched diverter circuit of claim 1, wherein the implanted lead has a length extending between and to a proximal end and a tissue-stimulating or biological-sensing electrode at or near a distal tip end.

21. The switched diverter circuit of claim 20, wherein the energy dissipating surface is disposed at a point or an area spaced from the electrode.

22. The switched diverter circuit of claim 21, wherein the energy dissipating surface is disposed within the blood flow of a patient.

23. The switched diverter circuit of claim 21, wherein the energy dissipating surface comprises a ring electrode.

24. The switched diverter circuit of claim 20, further comprising a lead housing supporting said leadwire distal tip electrode at one end thereof, said lead housing including a conductive housing portion forming the energy dissipating surface, and an insulator housing portion between said distal tip electrode and said conductive housing portion.

25. The switched diverter circuit of claim 1, including an impeding circuit associated with the diversion circuit, for raising the high-frequency impedance of the implanted lead.

26. The switched diverter circuit of claim 25, wherein the impeding circuit comprises an inductor.

27. The switched diverter circuit of claim 25, wherein the impeding circuit comprises a bandstop filter.

28. The switched diverter circuit of claim 26 or 27, wherein the diversion circuit comprises a resistor.

29. The switched diverter circuit of claim 26 or 27, wherein the diversion circuit comprises a low pass filter.

30. The switched diverter circuit of claim 29, wherein the low pass filter comprises a capacitor, an inductor, a Pi filter, a T filter, an LL filter, or an “

n”

element filter.

31. The switched diverter circuit of claim 26 or 27, wherein the diversion circuit comprises at least one series resonant L-C trap filter.

32. The switched diverter circuit of claim 31, wherein the diversion circuit comprises a plurality of L-C trap filters resonant respectively at different MRI frequencies.

33. The switched diverter circuit of claim 29, wherein the diversion circuit comprises a resistor.

34. The switched diverter circuit of claim 31, wherein the diversion circuit comprises a resistor.

35. The switched diverter circuit of claim 15, wherein said diversion circuit comprises a unipolar or multipolar feedthrough capacitor.

36. The switched diverter circuit of claim 1, wherein the energy dissipating surface comprises convolutions or fins, for increasing the surface area thereof.

37. The switched diverter circuit of claim 1, wherein the energy dissipating surface includes a roughened surface.

38. The switched diverter circuit of claim 37, wherein the roughened surface is formed through plasma or chemical etching, porous or fractal coatings or surfaces, whiskers, morphologically designed columbar structures, vapor, electron beam or sputter deposition of a high surface area energy conductive material, or a carbon nanotubes.

39. The switched diverter circuit of claim 1, wherein the implanted lead comprises at least a portion of a probe or a catheter.

40. The switched diverter circuit of claim 39, wherein the energy dissipating surface is selected from the group consisting essentially of a sheath, an insulative body, or a thermally conductive element.

41. The switched diverter circuit of claim 1, wherein the implanted lead comprises at least a pair of leads each having a length extending between and to a proximal end and a tissue-stimulating or biological-sensing electrode at a distal tip end.

42. The switched diverter circuit of claim 41, wherein said diversion circuit couples each of said leads to the energy dissipating surface which is disposed at a point or an area distant from each of said electrodes.

43. The switched diverter circuit of claim 41 or 42, wherein said diversion circuit is coupled between said pair of leads.

44. The switched diverter circuit of claim 18, wherein said diversion circuit is mounted within said housing.

45. The switched diverter circuit of claim 44, wherein said housing is hermetically sealed.

46. The switched diverter circuit of claim 44, wherein said active implantable medical device (AIMD) comprises a deep brain stimulator.

47. The switched diverter circuit of claim 46, wherein said housing is adapted for mounting in thermal communication with a patient'"'"'s skull.

48. The switched diverter circuit of claim 46, further comprising an electrode shaft assembly having a proximal end carried by said housing, said at least one lead extending through said electrode shaft assembly and having said distal tip end electrode for contacting patient brain tissue.

49. The switched diverter circuit of claim 24, wherein said distal tip electrode cooperates with said conductive and insulator housing portions to define a hermetically sealed package having said diversion circuit mounted therein.

50. The switched diverter circuit of claim 49, wherein said hermetically sealed package has a generally tubular shape with said distal tip electrode mounted at one end thereof, and further defining a hermetic seal assembly at an opposite end thereof, said lead extending through said hermetic seal assembly.

51. The switched diverter circuit of claim 49, further comprising an impeding circuit associated with said diversion circuit and mounted within said hermetically sealed package.

52. The switched diverter circuit of claim 51, wherein said impeding circuit comprises at least one inductor.

53. The switched diverter circuit of claim 52, wherein said at least one inductor comprises an inductor chip.

54. The switched diverter circuit of claim 52, wherein said at least one inductor comprises an inductor wire wound onto a ferromagnetic or non-ferromagnetic mandrel.

55. The switched diverter circuit of claim 49, wherein said diversion circuit comprises at least one capacitor coupled between said leadwire and said energy dissipating surface.

56. The switched diverter circuit of claim 52, wherein said at least one inductor comprises two inductor elements disposed in series, said diversion circuit being coupled between said pair of inductor elements and said energy dissipating surface.

57. The switched diverter circuit of claim 56, wherein said diversion circuit comprises at least one capacitor.

58. The switched diverter circuit of claim 49, wherein said diversion circuit comprises at least one L-C trap filter coupled between said lead and said energy dissipating surface.

59. The switched diverter circuit of claim 58, wherein said at least one L-C trap filter comprises a plurality of L-C trap filters resonant respectively at different MRI frequencies.

60. The switched diverter circuit of claim 1, further comprising means for hermetically sealed mounting of said energy dissipating surface along said lead between proximal and distal ends thereof, said hermetically sealed means defining a chamber having said diversion circuit mounted therein.

61. The switched diverter circuit of claim 60, wherein said lead comprises a first lead having a tip electrode at a distal end thereof, and a second lead having a ring electrode at a distal end thereof, said first and second leads having said energy dissipating surface disposed in hermetically sealed relation therewith and extending through said chamber, said diversion circuit coupling said first and second leads to said energy dissipating surface.

62. The switched diverter circuit of claim 61, wherein said diversion circuit comprises a unipolar or multipolar feedthrough capacitor.

63. The switched diverter circuit of claim 60, further comprising an impeding circuit associated with said diversion circuit and mounted within said hermetically sealed chamber.

64. The switched diverter circuit of claim 20, wherein the energy dissipating surface comprises a probe or a catheter.

65. The switched diverter circuit of claim 64, wherein said electrode comprises an ablation tip electrode.

66. The switched diverter circuit of claim 65, further comprising a probe housing having said ablation tip electrode at or near a distal end thereof, wherein said energy dissipating surface is disposed at a point or an area distant from said ablation tip electrode, said diversion circuit diverting high frequency energy away from said ablation tip electrode to said energy dissipating surface.

67. The switched diverter circuit of claim 66, wherein said implanted lead comprises a first lead having said ablation tip electrode at or near a distal end thereof, at least one second lead having a ring electrode at or near a distal end thereof, said diversion circuit diverting high frequency energy away from said ablation tip and said ring electrodes to said energy dissipating surface.

68. The switched diverter circuit of claim 1, wherein the energy dissipating surface comprises at least a portion of a handle for a probe or catheter.

69. The switched diverter circuit of claim 1, wherein the energy dissipating surface is disposed within an insulative sheath.

70. The switched diverter circuit of claim 1, wherein the energy dissipating surface comprises a plurality of spaced-apart energy dissipating surfaces.

71. The switched diverter circuit of claim 20, including a tether disposed between and conductively coupling the electrode and the energy dissipating surface.

72. The switched diverter circuit of claim 20, wherein the electrode comprises a paddle electrode disposed on a first side of a paddle.

73. The switched diverter circuit of claim 72, wherein the energy dissipating surface is disposed on a second side of the paddle.

74. The switched diverter circuit of claim 73, wherein the diversion circuit comprises a capacitive element disposed within the paddle between the electrode and the energy dissipating surface.

75. The switched diverter circuit of claim 74, wherein the capacitive element comprises a discrete capacitor.

76. The switched diverter circuit of claim 74, wherein the capacitive element comprises parasitic capacitance.

77. The switched diverter circuit of claim 72, wherein the energy dissipating surface is attached to the paddle.

78. The switched diverter circuit of claim 1, wherein the energy dissipating surface comprises a material capable of being visualized during a magnetic resonance scan.

79. The switched diverter circuit of claim 18, wherein the diversion circuit comprises a short to the housing.

80. The switched diverter circuit of claim 1, wherein the energy dissipating surface includes a biomimetic coating.

81. The switched diverter circuit of claim 1, wherein the diversion circuit includes at least one non-linear circuit element.

82. The switched diverter circuit of claim 81, wherein the at least one non-linear circuit element comprises a transient voltage suppressor.

83. The switched diverter circuit of claim 81, wherein the at least one non-linear circuit element comprises a diode.

84. The switched diverter circuit of claim 1, including a switch associated with the implanted lead, for electrically opening the implanted lead without substantial degradation of the transfer to the energy dissipating surface of the high frequency energy induced on the implanted lead at the selected RF frequency or frequency band.

85. The switched diverter circuit of claim 1, 2, 8, or 18, wherein the diversion circuit comprises a high pass filter.

86. The switched diverter circuit of claim 85, wherein the high pass filter prevents low frequency gradient field-induced energy in the implanted lead or the leadwire from passing through the diversion circuit to the energy dissipating surface.

87. The switched diverter circuit of claim 85, wherein the high pass filter comprises a capacitor.

88. The switched diverter circuit of claim 87, wherein the high pass filter comprises a resistor in series with a capacitor.

89. The switched diverter circuit of claim 85, wherein the high pass filter comprises an LC trap filter.

90. The switched diverter circuit of claim 18, wherein the diversion circuit is disposed within the housing for the AIMD.

91. The switched diverter circuit of claim 18, wherein the diversion circuit is disposed within a header block for the AIMD.

92. The switched diverter circuit of claim 20, wherein the diversion circuit is disposed at or adjacent to the proximal end of the implanted lead.

93. The switched diverter circuit of claim 91, wherein the diversion circuit is disposed in a proximal lead connector.

94. The switched diverter circuit of claim 18, including an EMI shield conductively coupled to the housing and coaxially extending about the leadwire in non-conductive relation.

95. The switched diverter circuit of claim 93, wherein the diversion circuit is conductively coupled to the EMI shield.