METHODS AND APPARATUS FOR FABRICATING LEADS WITH CONDUCTORS AND RELATED FLEXIBLE LEAD CONFIGURATIONS

• US 20080262584A1
• Filed: 03/13/2008
• Published: 10/23/2008
• 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: Shifflette, J. Michael, Bottomley, Paul A., Karmarkar, Parag V., Piferi, Peter, Gore, Brian, Allen, Justin M., Edelstein, William A.
• Granted Patent: US 9,248,270 B2
• Time in Patent Office: Days
• US Class Current: 607/119
• CPC Class Codes: A61N 1/0488 Details about the lead
• 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 1/086 Magnetic resonance imaging [MRI] compatible leads
• CPC Class Codes: B29C 33/126 using centering means forming part of the insert
• CPC Class Codes: B29L 2031/753 Medical equipment; Accessories therefor bloodbags, medical bags B29L2031/7148; artificial eyes B29L2011/0008
• CPC Class Codes: G01N 3/32 by applying repeated or pulsating forces
• CPC Class Codes: Y10T 29/49071 by winding or coiling

Abstract

MRI/RF compatible leads include at least one conductor, a respective conductor having at least one segment with a multi-layer stacked coil configuration. The 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 leads and methods of fabricating leads are also described.

Claims

1. An RF/MRI compatible lead comprising:

at least one conductor having a length with opposing distal and proximal end portions, the at least one conductor having at least one segment with a multi-layer coil configuration comprising a first forward coiled section that extends in a forward lengthwise direction for a first forward physical length, then turns to merge into a proximately positioned reverse coiled section that extends in a substantially opposing reverse lengthwise direction for a reverse physical length, then turns to merge into a proximately positioned second forward coiled section that extends in the forward lengthwise direction for a second forward physical length.

2. A lead according to claim 1, wherein at least two of the first forward section, the second forward section, and the reverse coiled section have substantially constant diameter coil configurations.

3. A lead according to claim 1, wherein the first forward coiled section, the second forward coiled section and the reverse coiled section are substantially concentric.

4. A lead according to claim 1, wherein at least some revolutions of the forward and reverse coiled sections reside proximate each other in a side-to-side lengthwise orientation.

5. A lead according to claim 1, wherein at least some revolutions of the reverse coiled section reside proximate and over the first forward coiled section.

6. A lead according to claim 1, wherein at least some revolutions of the reverse coiled section are interleaved with at least some revolutions of at least one of the forward coiled sections.

7. A lead according to claim 1, wherein the forward coiled section extends in the lengthwise direction about a central axis and has a pitch such that serial revolutions of the forward coiled section are spaced apart in a lengthwise direction to define gaps, and wherein the reverse coiled section extends about the central axis and has a pitch such that revolutions thereof substantially reside in the gaps of the forward coiled section.

8. A lead according to claim 1, wherein the second forward coiled section has more revolutions than that of the first forward and the reverse coiled section.

9. A lead according to claim 1, wherein the first forward coiled section resides on a first layer, the reverse coiled layer resides on a second layer over the first layer, and the second forward coiled section resides on a third layer over the second layer to define a three-layer stacked conductor coil configuration.

10. A lead according to claim 1, wherein the first coiled forward section and the reverse coiled section reside on a substantially common layer and the second coiled forward section resides over the first forward and reverse coiled sections to define a two-layer stacked conductor coil configuration.

11. A lead according to claim 1, wherein the first coiled forward section and the reverse coiled section have substantially the same pitch, and wherein the second forward coiled section has a smaller pitch than that of the first and reverse coiled sections.

12. A lead according to claim 1, wherein the at least one conductor is a plurality of conductors, each having at least one segment with a multi-layer stacked coil configuration of at least one set of the first and second forward coiled sections and the reverse coiled section.

13. A lead according to claim 12, wherein the first coiled forward section and the reverse coiled section have substantially the same pitch, and wherein the second forward coiled section has a smaller pitch than that of the first and reverse coiled sections.

14. A lead according to claim 1, wherein at least one segment of the multi-stacked coil configuration has more than three layers of stacked coils.

15. A lead according to claim 1, wherein the at least one conductor is a plurality of conductors wherein each of the conductors are insulated.

16. A lead according to claim 1, further comprising a flexible polymeric outer layer encasing the at least one conductor and configured so that at least a major portion of the length of the lead has a substantially constant outer diameter.

17. A lead according to claim 1, wherein the further comprising an elongate inner flexible sleeve residing about a central lengthwise axis with the multi-layer stacked coil configuration encircling the sleeve.

18. A lead according to claim 1, wherein the at least one conductor includes a conductor that has a cross-sectional width of between about 0.0001 inches to about 0.2 inches.

19. A lead according to claim 1, wherein the lead is an MRI/MRS compatible implantable medical lead.

20. A lead according to claim 1, further comprising at least one electrode, and wherein the lead comprises a plurality of conductors, one or more of the conductors in communication with the at least one electrode.

21. A lead according to claim 1, wherein the lead is flexible and the at least one conductor has low DC resistance.

22. A lead according to claim 20, wherein the lead is configured so that the lead heats local tissue less than about 10 degrees Celsius or does not heat local tissue when a patient is exposed to target RF frequencies generating a peak input SAR of between about 4 W/kg to about 10 W/kg and/or whole body average SAR of between about 2 W/kg to about 4 W/kg.

23. A lead according to claim 1, wherein the conductor has at least two segments of the multi-layer stacked coil configuration, and wherein a forward section on a top layer of one multi-layer stacked coil configuration in one segment merges into a forward section on a bottom layer of the other segment.

24. A lead according to claim 20, 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.

25. A lead according to claim 1, wherein the elongate electrical lead comprises a plurality of conductors, and wherein each of the plurality of conductors is a continuous length of conductor, and wherein the lead is flexible.

26. A lead according to claim 1, wherein the at least one conductor has a plurality of multi-stacked segments serially arranged so that one segment merges into the next adjacent segment along the length of the conductor, each of the multi-stacked segments having a length that is less than about 15 cm, and wherein the lead has low DC resistance.

27. A lead according to claim 1, wherein the at least one conductor is a plurality of conductors configured so that at least one multi-stacked segment of a first conductor has coiled sections that are substantially concentric to coiled sections of at least one multi-stacked segment of a second conductor.

28. A lead according to claim 1, wherein the at least one conductor is a plurality of conductors configured so that one multi-stacked segment of a first conductor resides downstream or upstream of one multi-stacked segment of a second conductor along a length of the lead.

29. A lead according to claim 1, wherein the at least one conductor is between about 1-100 conductors.

30. A lead according to claim 29, wherein at least a majority of the conductors has a plurality of the multi-stacked coil configurations, and wherein the at least one conductor has between about 4-100 multi-stacked segments along the length thereof.

31. A lead according to claim 1, wherein the lead comprises first and second insulated conductors, each having a plurality of segments with the multi-stacked coil configuration, and wherein the segments of the multi-stacked coil configurations of the first conductor alternate along the length of the lead with those of the segments of the multi-stacked coil configurations of the second conductor.

32. A lead according to claim 1, wherein the lead is sufficiently flexible such that when grasped or suspended at a medial location, opposing long sides and/or end portions thereof drape or droop together.

33. A lead according to claim 1, wherein the at least one conductor comprises a single layer coil extension extending from a segment having a multi-stacked coil configuration to an electrode residing upstream thereof.

34. A method of fabricating a lead, comprising:

winding at least one conductor about a mandrel in a forward lengthwise direction to form a forward coil;

then

winding the at least one conductor over the mandrel in a reverse lengthwise direction to form a reverse coil.

35. A method according to claim 34, further comprising providing a sleeve over the mandrel before the winding steps.

36. A method according to claim 34, further comprising, after winding the at least one conductor to form the reverse coil, winding the at least one conductor in the forward lengthwise direction again to form another forward coil over the underlying forward and reverse coils, then automatically repeating the winding steps to create between about 2-100 stacked coil configurations for a respective conductor.

37. A method according to claim 34, further comprising, after the step of winding the at least one conductor to form the reverse coil, winding the at least one conductor over the mandrel in the forward lengthwise direction again to:

(a) form an upper layer forward coil over the forward and reverse coils; and

(b) form a lower layer of another forward coil upstream of the first forward and reverse coils.

38. A method according to claim 37, wherein the winding steps form the conductor into multiple layers of stacked coils.

39. A method according to claim 34, further comprising tensioning a wire mandrel during the winding operations.

40. A method according to claim 34, wherein the conductor has a transverse cross-sectional width of between about 0.0001 inches to about 0.2 inches.

41. A method according to claim 34, further comprising forming a flexible outer layer onto the coiled conductor.

42. A method according to claim 41, wherein the forming step comprises extruding, drawing down or injection molding the outer layer.

43. A method according to claim 41, wherein the forming step comprises placing the wound conductor while held on the mandrel and/or sleeve in a mold, then flowably introducing a moldable material into the mold over the wound conductor, and forming the sleeve to be an integral part of the lead.

44. A method according to claim 34, wherein the at least one conductor is a plurality of conductors.

45. A method according to claim 34, further comprising repeating the winding steps to form a plurality of connected sets of forward, reverse and forward coil sections spaced along the lengthwise direction of the at least one conductor.

46. A method according to claim 34, wherein the winding the forward and reverse coils comprises substantially concentrically winding the respective coils in revolutions about a central axis defined by the forming mandrel, the central axis extending in the lengthwise direction.

47. A method according to claim 34, wherein the winding the forward coil is carried out by winding the conductor at a first pitch in one of a clockwise or counter clockwise direction, wherein the winding the reverse coil is carried out by winding the conductor at the same first pitch in an opposing clockwise or counterclockwise rotational direction such that revolutions of the reverse coil section resides in a gap left by the forward coil alternating with revolutions of the forward coil.

48. A method according to claim 34, wherein the winding the reverse coil comprises stacking at least some revolutions of the reverse coil above at least some revolutions of the forward coil.

49. A method according to claim 34, wherein the winding the forward coil comprises leaving gap spaces between at least some adjacent revolutions thereof, and wherein the winding the reverse coil comprises placing a respective revolution of the reverse coil in a respective gap space formed by the forward coil so that at least some revolutions of the forward and reverse coils reside side by side in an interleaved pattern.

50. A method according to claim 34, wherein the winding the reverse coil comprises winding the revolutions of the reverse coil over revolutions of the forward coil in a second coil layer, and wherein the method further comprises winding a second forward coil over the reverse coil in a third coil layer to form a tri-layer stacked coil configuration.

51. A method according to claim 50, wherein the winding pitch of the forward coil of the first layer is substantially the same as that of the reverse coil of the second layer, and wherein the winding pitch of the forward coil of the third layer is smaller (closer) than the pitch of the first and second layers.

52. A method according to claim 51, wherein the rotational winding direction of the first, second and third layers of coils is the same.

53. A method according to claim 34, wherein the at least one conductor is a plurality of conductors that are cowound to form at least one multi-layer stacked coil configuration.

54. A method according to claim 51, wherein each of the coils of the first, second and third layers has an associated number of revolutions, and wherein the third layer coil has at least about twice that of the first and second layer coils.

55. A method according to claim 34, wherein the winding steps are carried out so that the forward and reverse coils are on first layer, the method further comprising winding another forward section on a second layer over the forward and reverse coils of the first layer, wherein each of the coils of the first and second layers has an associated number of revolutions, and wherein the second layer coil has at least about twice that of the first and second layer coils.

56. A method according to claim 34, wherein the winding steps are carried out so that the forward and reverse coils are on first layer, the method further comprising winding another forward section on a second layer over the forward and reverse coils of the first layer, wherein the first layer forward coil is wound in a clockwise or counter clockwise direction, the reverse coil is wound in an opposing clockwise or counter clockwise direction and the second layer forward coil is wound in the same rotational direction as the reverse coil direction.

57. A method according to claim 34, wherein the lead is configured so that the lead heats local tissue less than about 10 degrees Celsius or does not heat local tissue when a patient is exposed to target RF frequencies at a peak input SAR of between about 4 W/kg to about 10 W/kg and/or whole body average SAR of between about 2 W/kg to about 4 W/kg.

58. A method according to claim 34, wherein the forming mandrel can have a outer diameter of between about 0.0001 inches to about 0.2 inches.

59. A method according to claim 34, further comprising sterilizing the lead and packaging the lead a medical lead before or after the sterilizing step.

60. A method of molding an encasement layer onto a medical lead, comprising:

attaching at least one spiral strip of material to an outer surface of at least one conductor;

then

molding an outer layer onto the conductor to form a flexible medical electrical lead.

61. A method according to claim 60, wherein the attaching step comprises applying a strip of silicone to the outer surface of the conductor.

62. A mold for an implantable medical lead, comprising:

a lower member having an elongate channel;

an upper member having an elongate channel sized and configured to matably attach to the lower member such that the upper and lower member channels are aligned to define a mold cavity; and

at least one conductor sized and configured to reside in the mold cavity, wherein at least one of the upper and lower members has a mold material introduction port in communication with the mold cavity, and wherein the mold is sized and configured to mold a flexible overmold layer on the at least one conductor.

63. A mold according to claim 62, wherein the upper and lower member channels have a shallow depth of between about 0.001 inches to about 0.2 inches, and a length of between about 1 cm to about 150 cm.

64. A mold according to claim 62, wherein the lead subassembly comprises a flexible spiral strip on an outer surface thereof that snugly positions the lead subassembly in the mold cavity.

65. A mold according to claim 62, wherein the mold cavity is open at least one end of the upper and lower members, wherein the at least one conductor comprises a sleeve over forming mandrel extending axially through a center thereof, and wherein the sleeve forms an integral portion of the lead and the mandrel is removed before, during or after the molding.

66. An electrical lead subassembly, comprising:

at least one conductor comprising at least one spiral line of flexible material over an outer surface thereof.

67. An electrical lead subassembly according to claim 66, wherein the at least one spiral line of material comprises at least one strip of silicone.

68. An RF/MRI compatible medical lead comprising:

at least one continuous conductor having a length, a respective conductor having at least one segment with a plurality of closely spaced substantially concentric coils that are arranged so that at least some revolutions of one coil reside over at least some revolutions of another coil.

69. A medical lead according to claim 68, wherein the lead is flexible and comprises first and second conductors and a plurality of electrodes and has low DC resistance, the first conductor having a plurality of the segments of coils and being in communication with one of the electrodes and the second conductor having a plurality of the segment of coils being in communication with another one of the electrodes.

70. A medical lead according to claim 68, wherein the lead is flexible and comprises at least first and second conductors and at least one electrode and has low DC resistance, the first conductor having a plurality of the segments of coils and being in communication one of the electrodes and the second conductor having a plurality of the segment of coils and being in communication with the same electrode as the first conductor.

71. A flexible medical lead having at least one conductor with at least one multi-layer stacked coil configuration with the conductor turning back on itself in a lengthwise direction at least twice in the stacked coil configuration, wherein the at least one conductor merges at a distal end portion thereof into a forward coil section that connects to an electrode.

72. A flexible medical lead according to claim 71, wherein the lead is a cardiac lead.

73. A flexible medical lead according to claim 71, wherein the lead is an implantable cardiac lead.

74. A flexible medical lead according to claim 71, wherein the lead is a neuromodulation lead.

75. A flexible medical lead according to claim 71, wherein the lead is an implantable deep brain stimulation lead.

76. A flexible medical lead according to claim 71, wherein the lead is a spinal cord stimulation lead.

77. A flexible medical lead according to claim 71, wherein the lead is an interventional electrophysiology cardiac lead.

78. A medical lead having at least first and second conductors, the first and second conductors having at least one multi-layer stacked cowound coil configuration with a respective first forward coiled section that extends in a forward lengthwise direction for a first forward physical length, that then turns in a lengthwise direction to merge into a proximately positioned reverse coiled section that extends in a substantially opposing reverse lengthwise direction for a reverse physical length, and that then turns in the lengthwise direction to merge into a proximately positioned second forward coiled section that extends in the forward lengthwise direction.

79. A medical lead according to 78, wherein the lead further comprises at least one electrode, and wherein each of the first and second conductors connect to the same electrode.

80. A medical lead according to 78, wherein the lead further comprises a plurality of electrodes, and wherein the first and second conductors connect to a different electrode.

81. An active fixation cardiac lead comprising:

at least one conductor having at least one multi-layer stacked coil configuration whereby the conductor turns in a longitudinal direction on itself at least twice in communication with a screw electrode, wherein the screw electrode can be advanced to engage local tissue.

82. An automated fatigue testing apparatus, comprising:

a wheel in communication with a linear slide defining a linear translation member;

a connection rod having first and second opposing end portions, the first end portion attached to the wheel;

an automated drive member in communication with the wheel to cause the wheel to rotate at a desired speed;

a slide block attached to the other end portion of the connection rod;

a rotating gear attached to the slide block and in communication with a rack gear; and

a test specimen holder in communication with the rotating gear whereby a test specimen is automatically repeatedly exposed to linear and rotational forces for a desired number of cycles or until fracture or failure of test parameters associated with fatigue of the test specimen.

83. An automated testing apparatus according to claim 82, wherein the rack gear is slidably adjustable relative to the slide block to cooperate with interchangeable different size diameter rotating gears to adjust rotational forces on the test specimen.

84. An automated testing apparatus according to claim 82, wherein the rotating wheel comprises a plurality of circumferentially spaced apart mounting pin apertures located at different radial positions from a center of the rotating wheel, wherein the connection rod is attached to a mounting pin at the first end portion thereof that resides in a selected one of the apertures to allow for linear movement adjustment of the slide block.