MRI AND RF COMPATIBLE LEADS AND RELATED METHODS OF OPERATING AND FABRICATING LEADS

• US 20080243218A1
• Filed: 03/13/2008
• Published: 10/02/2008
• Est. Priority Date: 03/19/2007
• Status: Active Grant

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation), MRI Interventions, Inc. (Clearpoint Neuro, Inc.)
• Original Assignee: MRI Interventions, Inc. (Clearpoint Neuro, Inc.)
• Inventors: Bottomley, Paul A., Karmarkar, Parag V., Allen, Justin M., Edelstein, William A.
• Granted Patent: US 9,492,651 B2
• Time in Patent Office: Days
• US Class Current: 607/116
• 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 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: A61N 1/05 for implantation or insertion into the body, e.g. heart electrode A61N1/06 takes precedence
• CPC Class Codes: A61N 1/0565 Electrode heads
• 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: Y10T 29/49117 Conductor or circuit manufacturing

Abstract

RF/MRI compatible leads include at least one conductor that turns back on itself at least twice in a lengthwise direction, and can turn back on itself at least twice at multiple locations along its length. The at least one electrical lead can be configured so that the lead heats local tissue less than about 10 degrees Celsius (typically about 5 degrees Celsius or less) or does not heat local tissue when a patient is exposed to target RF frequencies at a peak input SAR of at least about 4 W/kg and/or a whole body average SAR of at least about 2 W/kg. Related devices and methods of fabricating leads are also described.

Claims

1. An RF/MRI compatible medical device comprising:

an elongate electrical medical lead comprising at least one conductor with opposing proximal and distal portions, the at least one conductor having a first section that extends in a first lengthwise direction for a first physical length, then turns to define at least one reverse section that extends in a substantially opposing lengthwise direction for a second physical length, then turns again to define a third section that extends in the first lengthwise direction for a third physical length.

2. A medical device according to claim 1, wherein the first, second and third physical lengths are proximately located with respect to each other and occupy a sub-portion of an overall length of the at least one conductor.

3. A medical device according to claim 1, wherein the lead is configured so that the lead heats local tissue less than about 5 degrees Celsius or does not heat local tissue when a patient is exposed to target RF frequencies at a peak input SAR of at least about 4 W/kg and/or a whole body average SAR of at least about 2 W/kg.

4. A medical device according to claim 1, wherein the electrical lead heats local tissue less than about 2 degrees Celsius when exposed to target RF frequencies associated with MR Scanners at a peak input SAR of between about 4 W/kg and/or a whole body average SAR of at least about 2 W/kg.

5. A medical device according to claim 1, wherein the electrical lead heats local tissue less than about 5 degrees Celsius when exposed to target RF frequencies associated with MR Scanners at a peak input SAR of between about 4-10 W/kg and/or a whole body average SAR of between about 2-5 W/kg.

6. A medical device according to claim 1, wherein the at least one conductor is a plurality of conductors, and wherein each of the plurality of conductors comprises a continuous single length of conductor with each having at least one set of the first, second and third conductor sections, and wherein the lead is flexible.

7. A medical device according to claim 1, wherein the at least one conductor is a plurality of conductors, each respective conductor having a plurality of sets of the first, second and third sections residing along the length of a respective conductor between the opposing distal and proximal portions.

8. A medical device according to claim 1, wherein the first, second and third sections of the at least one conductor reside proximate each other, and wherein the at least one conductor has a plurality of sets of the first, second and third sections spaced apart along the length thereof to define a plurality of reverse sections.

9. A medical device according to claim 1, wherein the at least one conductor turns on itself a plurality of times in opposing lengthwise directions to define a plurality of the first and third forward sections separated by a corresponding reverse section so that some of the reverse sections reside proximate each other along a substantially common lengthwise portion of the lead.

10. A medical device according to claim 1, wherein at least one of the sections has a coiled portion.

11. A medical device according to claim 8, wherein at least one of the first, third or third sections extends under, over or through a neighboring section.

12. A medical device according to claim 10, wherein at least one of the sections resides proximate to and outside of a coiled portion of another section.

13. A medical device according to claim 1, wherein the third forward section resides proximate the first forward section with the second reverse section therebetween.

14. A medical device according to claim 1, wherein the first, second and third sections occupy a minor length of an overall length of the conductor, and wherein the conductor is configured so that a first set of turns forming the first, second and third sections merge into a second set of turns forming another segment of first, second and third sections.

15. A medical device according to claim 1, wherein the conductor has greater than two sets of turns forming first, second and third sections a plurality of times in a lengthwise spaced apart relationship, wherein the lead has a length of greater than 10 cm, and wherein the at least one conductor is in communication with an electrode and/or an implantable pulse generator.

16. A medical device according to claim 6, wherein the second reverse section has an electrical length that is about λ

/4 or less in an MRI scanner and a physical length that is substantially the same or between about 30-70% that of the physical length of at least one of the first and third forward sections.

17. A medical device according to claim 1, further comprising an implantable or external medical device connected to an end portion of the lead, and wherein the at least one elongate conductor is a plurality of conductors.

18. A medical device according to claim 1, wherein the at least one conductor is a plurality of conductors, each of the conductors having at least one set of the first, second and third sections, the lead further comprising a plurality of electrodes, at least one electrode connected to one or more of the plurality of conductors.

19. A medical device according to claim 1, wherein the at least one conductor is a plurality of conductors, and wherein the plurality of conductors include at least one respective coiled first, second or third sections that are co-wound together with at least one of the other conductors first, second or third sections at a substantially common physical lengthwise location.

20. A medical device according to claim 1, wherein the lead is adapted to suppress RF currents induced in the at least one lead by a MRI scanner during an MRI or MRS procedure.

21. A medical device according to claim 1, wherein the lead is configured to provide substantially broadband suppression of induced currents in the range of between about 20 MHz to about 200 MHz.

22. A medical device according to claim 1, wherein the lead is implantable and connected at one end portion to an implantable therapeutic device and/or a lead extension that connects to an implantable therapeutic device.

23. A medical device according to claim 22, wherein the at least one conductor is connected at the other end portion of the lead to at least one implantable electrode.

24. A medical device according to claim 22, wherein the implantable therapeutic device comprises an IPG (implantable pulse generator).

25. A medical device according to claim 1, wherein the lead is at least one of a cardiac pacemaker lead, a cardiac defibrillator lead, or a cardiac monitor lead.

26. A medical device according to claim 1, wherein the lead is an implantable brain neuromodulation or spinal cord stimulation lead.

27. A medical device according to claim 1, wherein the lead is configured to reject RF-induced voltages and/or currents over a broad band of RF frequencies in the range of between about 1 MHz-500 MHz.

28. A medical device according to claim 1, wherein the lead has an impedance that varies at different frequencies over target frequency ranges above DC (direct current) frequencies and defines a broadband low pass filter.

29. A medical device according to claim 1, wherein the lead impedance has local maxima in a target frequency range associated with an operating frequency of an MRI Scanner.

30. A medical device according to claim 28, wherein the wherein the lead has an impedance with at least two local impedance maxima corresponding to two RF MRI frequencies associated with MRI Scanners, including RF MRI frequencies corresponding to at least two of the following:

0.1 Tesla (T), 0.3 T, 0.7 T, 1.0 T. 1.5 T, 2.0 T, 2.5 T, 3 T, 4 T, 4.7 T, 7 T, and 9.4 T.

31. A medical device according to claim 1, wherein the at least one conductor comprises a distal end portion with a set of turns defining the first, second and third sections that merges into a distal coiled portion that connects to an electrode.

32. A medical device according to claim 1, wherein the lead is an implantable shielded flexible lead having a length of between about 3 cm to about 3 m, with a plurality of conductors, each of the conductors having a cross-sectional size of between about 0.001 inches to about 0.2 inches.

33. A medical device according to claim 1, wherein the distal end portion of the at least one conductor is connected to an electrocardiographic electrode and the proximal end portion is in communication with an electrocardiographic monitoring device.

34. A medical device according to claim 1, wherein the distal end portion of the at least one conductor is connected to an electroencephalographic electrode and the proximal end portion is in communication with an electroencephalographic monitoring device.

35. A medical device according to claim 1, wherein the distal end portion of the at least one conductor is connected to a blood pressure monitoring transducer and the proximal end portion is connected to a blood pressure monitoring device.

36. A medical device according to claim 7, wherein at least one end portion of the at least one conductor is connected to a blood oxygen monitoring transducer and at least another end is in communication with a blood oxygen monitoring device.

37. A medical device according to claim 1, wherein the lead comprises a plurality of conductors, with the at least one conductor having the first, second and third sections being configured with multiple sets of turns defining multiple first, second and third sections, and wherein the conductor with the multiple sets of turns resides over an inner conductor.

38. A medical device according to claim 1, wherein the lead comprises a plurality of conductors, with the at least one conductor having the first, second and third sections being configured with multiple sets of turns defining multiple first, second and third sections, and wherein the conductor with the multiple sets of turns is an inner conductor in communication with a screw electrode for active fixation.

39. A medical device according to claim 1, wherein the lead is a cardiac lead, and wherein the conductor is in communication with an extendable active fixation screw electrode.

40. An MRI/RF compatible medical lead system, comprising:

a lead comprising at least one conductor having a length with opposing proximal and distal end portions configured with a plurality of current suppression modules along the length thereof; and

at least one electrode in communication with the at least one conductor.

41. A medical lead according to claim 40, wherein the at least one conductor is continuous length of conductor, wherein the current suppression modules are serially arranged along at least a major portion of the physical length of the conductor so that one current suppression module merges into a proximately positioned neighboring current suppression module.

42. A medical lead system according to claim 40, wherein the at least one conductor is a continuous length of conductor and has a substantially constant non-adjustable physical length.

43. A medical lead system according to claim 40, wherein each current suppression module comprises a first forward segment extending in a forward lengthwise direction toward the at least one electrode in close proximity to a reverse segment that turns away from the forward segment and extends in an opposing reverse lengthwise direction from that of the forward segment, and a second forward segment that extends in the forward lengthwise direction, wherein the reverse segment has a physical length that is substantially the same or shorter than at least one of the at least one forward segments.

44. A medical lead system according to claim 40, wherein the lead system heats local tissue less than about 10 degrees Celsius when exposed to RF associated with an MRI Scanner at a peak input SAR of between about 4 W/kg to about 10 W/kg and/or a whole body average SAR input of between about 2-5 W/kg.

45. A medical lead system according to claim 40, wherein some of the current suppression modules have at least one coiled portion forming at least a portion of a respective forward and/or reverse segment thereof.

46. A medical lead system according to claim 40, wherein the current suppression modules have a plurality of closely spaced reverse segments with neighboring reverse segments connected by turns or bends merging into a forwardly extending segment.

47. A medical lead system according to claim 40, wherein at least some of the current suppression modules are configured so that a respective conductor turns on itself to reside above, below or through a coiled portion thereof.

48. A medical lead system according to claim 40, wherein the lead comprises a serpentine shape of a plurality of closely spaced lead turns that define a plurality of reverse segments, with each neighboring pair of reverse segments separated by a forwardly extending segment, wherein the serpentine reverse segments reside proximate each other along a substantially common lengthwise portion of the lead.

49. A medical lead system according to claim 40, wherein at least one of the reverse or forward segments extends under, over or through a coiled forward or reverse segment.

50. A medical lead system according to claim 40, wherein the at least one conductor is a plurality of conductors, and wherein the at least one electrode is a plurality of electrodes, and wherein one or more of the conductors are in electrical communication with each of the electrodes.

51. A medical lead system according to claim 40, wherein the at least one conductor is a plurality of conductors, and wherein the at least one electrode is a plurality of electrodes, and wherein at least two conductors are in electrical communication with each of the electrodes.

52. A medical lead system according to claim 40, wherein each current suppression module has two respective forward segments with an electrical length that is about λ

/4 or less in an MRI scanner, and wherein a corresponding reverse segment has an electrical length that is substantially the same, less or greater than that of at least one of the two forward segments.

53. A medical lead system according to claim 52, wherein the reverse segment has a lengthwise physical length that is substantially the same or less than that of a lengthwise physical length of at least one proximate forward segment.

54. A medical lead system according to claim 40, further comprising an implantable pulse generator (IPG) in communication with the at least one conductor of the lead system, with the IPG configured to provide an electrical stimulation or pacing signal to the at least one electrode through the at least one conductor.

55. A medical lead system according to claim 40, wherein at least some of the plurality of current suppression modules of the at least one conductor are proximately spaced apart in a lengthwise direction.

56. A medical lead system according to claim 40, wherein at least some of the plurality of current suppression modules of the at least one conductor are irregularly or regularly spaced apart in a lengthwise direction.

57. A medical lead system according to claim 40, wherein at least some of the current suppression modules have a configuration that is repeated over a length of the conductor.

58. A medical lead system according to claim 40, wherein some of the current suppression modules have a different physical and/or electrical length than others.

59. A medical lead system according to claim 40, wherein the conductors are insulated, the lead system further comprising an electrical insulator and/or RF shield of biocompatible material disposed over an external surface of the lead system.

60. A medical lead comprising:

at least one electrode; and

a lead with at least one conductor in communication with the at least one electrode, the at least one conductor having a first forward portion that extends in a lengthwise forward direction for a first physical distance toward the at least one electrode, then turns back at least once to define at least one rearward portion that travels in a substantially opposing lengthwise rearward direction for a second physical distance, and wherein the lead then turns back again to define a second forward portion that extends in the forward direction a third physical distance with a distal portion of the second forward portion residing beyond and downstream of the first forward portion.

61. A medical lead according to claim 60, wherein at least one of the first forward portion, the second forward portion or the rearward portion has a coiled segment.

62. A medical lead according to claim 60, wherein at least one of the first and second forward portions and the rearward portion have an electrical length that is about λ

/4 or less in an MRI scanner, and wherein the rearward portion has an electrical length that is substantially the same, less or greater than the first and second forward portions and a physical length that is between about 30-70% that of at least one of the first and second forward portions.

63. A lead comprising:

at least one conductor having a plurality of spaced apart current suppression modules, wherein at least one of the current suppression modules comprises a length of conductor having a plurality of closely spaced conductor portions in a serpentine shape.

64. A lead according to claim 63, wherein the serpentine shape of closely spaced conductor portions include conductor segments that extend in a lengthwise direction with bend portions therebetween that reside within a substantially common localized lengthwise extending region of the lead.

65. A lead according to claim 63, wherein one of the lengthwise extending conductor segments comprises a coiled portion with at least some of the closely spaced serpentine portions residing inside, outside or through the coiled portion.

66. A lead according to claim 63, wherein the conductor portions in the serpentine shape have a lengthwise physical distance of between about 0.5 cm to about 10 cm.

67. A lead according to claim 63, wherein the lead comprises an electrical shield, and wherein at least some of the serpentine conductor portions are unshielded to thereby increase RF-induced current deposited on the serpentine conductor portions relative to other conductor portions when exposed to RF associated with an MRI scanner.

68. A lead according to claim 63, wherein the conductor comprises first and second forward portions at least some opposing end portions of the serpentine shaped conductor portions, and wherein the first and second forward portions have increased insulation relative to the conductor portions in the serpentine shape.

69. A lead according to claim 63, wherein at least some of the conductor portions defining the serpentine shape are capacitively coupled together.

70. A lead according to claim 63, wherein the lead is a medical lead, wherein the at least one conductor is a plurality of conductors, each conductor extending to an electrode, and wherein each of the conductors comprise a plurality of the current suppression modules with serpentine shapes with the respective serpentine shapes being longitudinally spaced apart.

71. An MRI safe lead system, comprising:

an elongate flexible lead with a plurality of conductors having a length with opposing proximal and distal end portions, the conductors each having a plurality of current suppression modules extending along the length of the conductor, each current suppression module comprising at least one coiled segment; and

a plurality of electrodes, one or more of the conductors in communication with a respective one of the electrodes.

72. A lead system according to claim 71, wherein the lead system is configured to inhibit undesired temperature rise in local tissue to less than about 10 degrees Celsius when exposed to RF frequencies associated with the MRI scanner at a peak SAR input of between about 4 W/kg to at least about 10 W/kg and/or a whole body average SAR of between about 2 W/kg to at least about 5 W/kg.

73. A lead system according to claim 71, wherein corresponding sets of forward and rearward portions of a respective current suppression module have an electrical length of about λ

/4 or less in an MRI scanner, and wherein the forward portions have a lengthwise physical length of between about 1-25 cm, and wherein the rearward portions have a lengthwise physical length of between about 1-25 cm.

74. A lead system according to claim 71, wherein the rearward portions of the current suppression modules have a physical length that is between about 30-70% that of a physical length of an adjacent forward portion.

75. A lead system according to claim 71, wherein the plurality of current suppression modules is between about 4-40.

76. A lead system according to claim 71, wherein the plurality of current suppression modules is between about 6-20.

77. A lead system according to claim 71, wherein the plurality of conductors is between about 2-100, and wherein the conductors are configured so that the coiled segments of at least some of the forward and/or rearward portions of the current suppression modules are cowound with at least one other conductor.

78. A lead system according to claim 71, wherein the lead is between about 1 French to about 10 French.

79. A lead system according to claim 71, wherein the conductors comprise a distal end portion with at least one of the current suppression modules that terminates into a forward coiled segment that connects to one of the electrodes.

80. An implantable flexible lead comprising a plurality of conductors extending between opposing proximal and distal end portions of the lead, one or more of the conductors being connected to at least one or a plurality of electrodes at least one of the proximal or distal end portions thereof, wherein at least some of the plurality of conductors are configured with at least one coiled conductor portion and at least one closely spaced serpentine shaped conductor portion.

81. An implantable flexible lead system according to claim 80, wherein at least one of the conductors is configured so that at least some of the serpentine shaped portion resides inside the coiled conductor portion of the respective conductor.

82. An implantable flexible lead system according to claim 80, wherein at least one of the conductors is configured so that at least some of the serpentine shaped portion resides above, below or to the side of the coiled portion.

83. An implantable flexible lead system according to claim 80, wherein at least one of the conductors has substantially straight conductor portions configured so that two conductor portions cross-over each other and extend in substantially opposing longitudinal directions.

84. An implantable flexible lead comprising at least first and second conductors extending between opposing proximal and distal end portions of the lead, one or more of the conductors connected to at least one of a plurality of electrodes at the distal end portion thereof, wherein the first and second conductors comprise a substantially straight portion and a coiled portion, wherein the straight portion of the first conductor extends in a lengthwise direction outside and proximate to the second conductor coiled portion or inside and through the second conductor coiled portion.

85. A method of fabricating a medical lead, comprising:

providing a length of at least one elongate conductor; and

turning the at least one conductor back on itself at least twice to define two forward portions that extend lengthwise in a forward direction and at least one rearward portion that travels in a substantially opposing rearward direction.

86. A method according to claim 85, after the turning step, forming a flexible implantable lead body and sterilizing and packaging the implantable lead body.

87. A method according to claim 86, wherein the providing step is carried out using a conductor having a cross-sectional width of between about 0.001 inches to about 0.2 inches.

88. A method according to claim 85, wherein the turning step is repeated a plurality of times to define a plurality of current suppression modules along a length of the conductor.

89. A method according to claim 85, wherein the turning step is carried out with the rearward portion having a second physical distance being substantially the same or less than that of at least one of the two forward portions.

90. A method according to claim 85, wherein the turning step comprises forming a conductor segment to have at least one longitudinally extending serpentine shape that merges into a substantially straight conductor segment.

91. A method according to claim 85, wherein the turning step comprises coiling the at least one conductor.

92. A method according to claim 85, further comprising attaching an electrode to a distal end portion of the conductor.

93. A lead comprising an elongate electrical conductor adapted to reside in a patient with a first forward extending segment having a corresponding first electrical and physical length, a second reversed segment of the electrical conductor in close proximity to the first segment and extending in a substantially opposing lengthwise direction from the first forward segment, wherein the second reversed segment has substantially the same or a shorter physical length than the first forward segment with substantially the same, less or greater electrical length as the first forward segment when exposed to RF in the range of between about 1 MHz to at least about 200 MHz.

94. A method of inhibiting heating local tissue and/or suppressing or offsetting common mode RF currents in an electrical lead configured to reside in a patient, the electrical lead comprising at least one conductor having a first forward section with a first physical forward length that turns to define at least one reversed section extending in a substantially opposing lengthwise direction from the first forward section, the at least one reversed section having a second physical reverse length with an electrical length that is substantially the same less or greater than that of the first forward section, the method comprising:

generating RF induced common mode current in the first forward section and the at least one reversed section of the conductor, whereby common mode current flows in the first forward section and the reversed section in substantially the same direction; and

offsetting the current in the first forward section and the reversed section at a localized region of the conductor between the first forward and the reversed section.

95. A method according to claim 94, further comprising placing the patient in an MRI scanner to carry out the generating step, then transmitting an electrical output to local tissue via an electrode in communication with the at least one conductor first forward and reverse sections and inhibiting the electrode from unduly heating local tissue in response to the offsetting step whereby the first forward and reverse sections suppress common mode current propagated to the electrode by the electrical lead.

96. A lead system adapted to provide substantial immunity to signals induced by virtue of proximity to an electromagnetic radiation source comprising:

at least one elongate conductor having a first elongate forward section that extends in a forward lengthwise direction for a first forward physical length, then turns to define at least one reverse section that extends in a substantially opposing reverse lengthwise direction for a reverse physical length, then turns again to define a second forward section with a forward physical length extending in the forward lengthwise direction.

97. A lead system according to claim 96, wherein the conductor comprises at least one serpentine shaped conductor segment.

98. A lead system according to claim 96, wherein at least one of the first forward section, the second forward section or the reverse section of the conductor comprises a coiled conductor segment.

99. A lead system according to claim 98, wherein the at least one reverse section has the same, less or greater electrical length as the first forward segment when exposed to electromagnetic fields having frequencies between about 1 MHz to at least about 1 GHz.

100. A lead system according to claim 96, wherein the lead system connects an external medical device to an implantable medical device.

101. A lead system according to claim 96, wherein the lead system connects two external medical devices in proximity to a patient during an MRI scan.

102. A lead system according to claim 96, wherein the electromagnetic radiation source is one of RADAR, communications transmission, television transmission, satellite transmission, extra-terrestrial and/or terrestrial based cellular transmission, and radio transmission.

103. A lead system according to claim 96, wherein the lead system is a human implantable lead system connecting an implantable device to an internal or external device.

104. A lead system according to claim 96, wherein the lead system interconnects two electronic devices, at least one of which resides proximate to but outside a human or animal body.

105. An RF/MRI compatible lead comprising at least one continuous length of conductor having at least one sub-portion where the conductor turns back on itself at least twice in a lengthwise direction.

106. A lead according to claim 105, wherein the lead is an intra-cardiac electrophysiology lead.

107. A lead according to claim 105, wherein the lead is an implantable cardiac medical lead.

108. A lead according to claim 107, wherein the conductor with the turns is in communication with a screw electrode for active fixation.

109. A lead according to claim 107, wherein the conductor with the turns is in communication with a distal electrode, and wherein the lead is configured for passive fixation.

110. A lead according to claim 105, wherein the lead is an interventional or implantable intra-brain lead.

111. A lead according to claim 105, wherein the lead is a spinal column stimulation lead.

112. A lead according to claim 105, wherein the lead is an external medical lead.

113. A lead according to claim 105, wherein the lead is a medical lead with an external portion and an internal portion.

114. A lead according to claim 105, wherein the sub-portion is configured so that a reverse segment has a physical length of between about 2-10 cm.

115. A lead according to claim 105, wherein the conductor turns back on itself at least twice at least four different lengthwise locations over its length.

116. A cable configured for use in or proximate to an MR Scanner bore, the cable comprising at least one conductor configured to turn back on itself at least twice in a lengthwise direction to define an RF-induced heat resistant cable.