Implantable Mri compatible Stimulation Leads And Antennas And Related Systems And Methods

• US 20080039709A1
• Filed: 08/09/2005
• Published: 02/14/2008
• Est. Priority Date: 08/09/2004
• Status: Active Grant

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Karmarkar, Parag
• Granted Patent: US 8,509,876 B2
• Time in Patent Office: Days
• US Class Current: 600/410
• CPC Class Codes: A61B 2017/00039 Electric or electromagnetic phenomena other than conductivity, e.g. capacity, inductivity, Hall effect
• CPC Class Codes: A61B 2090/374 NMR or MRI
• CPC Class Codes: A61B 2090/3954 magnetic, e.g. NMR or MRI
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 90/11 with guides for needles or instruments, e.g. arcuate slides or ball joints
• CPC Class Codes: A61B 90/37 Surgical systems with images on a monitor during operation
• CPC Class Codes: A61N 1/0529 Electrodes for brain stimulation
• CPC Class Codes: A61N 1/0534 Electrodes for deep brain stimulation
• CPC Class Codes: A61N 1/086 Magnetic resonance imaging [MRI] compatible leads

Abstract

In vivo medical stimulation probes include an elongate lead having at least one stimulation electrode disposed on a distal portion thereof. The probes may include a plurality of axially spaced apart RF chokes disposed on and/or in an axially extending shielding layer of the lead in advance of the at least one electrode to inhibit induced RF current from forming and/or traveling along the shielding layer.

Claims

1. An in vivo medical stimulation probe, comprising:

an elongate lead having at least one stimulation electrode disposed on a distal portion thereof and an axially extending shielding layer; and

a plurality of axially spaced apart RF chokes disposed on and/or in the shielding layer in advance of the at least one electrode to inhibit induced RF current from forming and/or traveling along the shielding layer.

2. A medical stimulation probe according to claim 1, the lead further comprising a recording/sensing electrode disposed at the distal portion.

3. A medical stimulation probe according to claim 1, wherein the lead is a flexible lead, and wherein the at least one electrode is a plurality of spaced apart electrodes, the lead further comprising a plurality of conductors held in a core of the lead, a respective one for each electrode, and wherein the shielding layer is discontinuous and is configured to surround the conductors over at least a major length of the lead and terminate at a lead location that is in advance of the electrodes.

4. A medical stimulation probe according to claim 3, further comprising an axially extending primary inner shield surrounding the core with the plurality of electrodes, wherein the discontinuous shielding layer is a second shield layer that is generally cylindrically disposed over the inner shielding layer, and wherein the primary and second shielding layers both terminate at a distal location of the lead that precedes the electrodes.

5. A medical stimulation probe according to claim 3, further comprising a first insulating dielectric layer disposed between the conductors and the primary inner shield, and a second insulting dielectric layer disposed between the primary inner shield and the secondary shield, wherein the conductors, the first and second insulating layers and the primary inner and second shield layers comprise MRI compatible materials, and wherein the RF chokes are formed in the secondary shield to provide an electrical length that is about λ

4 or less.

6. A medical stimulation probe according to claim 5, the lead further comprising a bio- and MRI-compatible outer polymeric layer.

7. A medical stimulation probe according to claim 1, wherein the lead is MRI-compatible and further comprises an MRI antenna that is configured to collect and transmit signal data in response to an applied RF excitation pulse in an MRI scanner system.

8. A medical stimulation probe according to claim 7, wherein the MRI antenna is a coaxial antenna having a signal receiving length of between about 1-4 cm.

9. A medical stimulation probe according to claim 1, wherein the lead is chronically implantable, and wherein the at least one electrode is a plurality of electrodes that are sized and configured to apply deep brain stimulation.

10. A medical stimulation probe according to claim 7, further comprising a connector disposed at a proximal end portion thereof, the connector configured to releasably serially attach to both an implantable pulse generator and an MRI scanner interface, thereby allowing bimodal operation of the lead.

11. A medical stimulation probe according to claim 7, wherein the lead is configured to have at least two operational modes, including a first MRI operational mode wherein the lead receives MRI signals from the MRI antenna and a second therapeutic operational mode wherein the lead delivers a stimulation pulse to the at least one electrode.

12. A medical stimulation probe according to claim 11, wherein the at least one electrode is a plurality of electrodes, at least one of which is configured as a recording electrode, and wherein the lead is configured to provide trimodal operation with a third operational mode wherein the lead receives micro-electrical signals from local tissue from the recording/sensing electrode.

13. A medical stimulation probe according to claim 11, wherein the MRI antenna is configured to receive signal from local tissue over about a distance of about 2.5 cm or less.

14. A medical stimulation probe according to claim 13, wherein the MRI antenna is axially spaced apart from the closest electrode a distance of about 1-4 cm.

15. A medical stimulation probe according to claim 9, wherein the lead has a length that is greater than 10 cm.

16. A chronically implantable deep brain stimulation and MRI imaging probe system, comprising:

an internal MRI-compatible elongate lead comprising an MRI antenna having axially extending, radially spaced apart first and second shielding layers and at least one core conductor, for internally receiving local in vivo MRI signals;

at least one electrode held on a distal portion of the lead that, in operation, is configured to generate a stimulation pulse to deep brain tissue;

a stimulation circuit in communication with the at least one electrode;

a MRI signal receiver circuit in communication with the MRI antenna;

a splitter circuit in communication with the stimulation and receiver circuits for electrically connecting either the MRI receive or stimulation circuit; and

means for inhibiting RF induced current on the second shield layer of the lead.

17. A deep brain stimulation and MRI imaging probe according to claim 16, further comprising a decoupling circuit to electrically decouple the MRI antenna during an MRI RF transmit operation.

18. A deep brain stimulation and MRI imaging probe according to claim 16, wherein the means for inhibiting comprises a plurality of axially spaced apart discontinuities in the second shield layer.

19. A deep brain stimulation and MRI imaging probe according to claim 16, wherein the means for inhibiting comprises axially spaced apart RF choke circuits in communication with the second shield layer.

20. A deep brain stimulation and MRI imaging probe according to claim 19, wherein the RF choke circuits comprise Balun circuits.

21. A deep brain stimulation and imaging probe according to claim 17, further comprising a microrecording electrode for receiving microelectric signals associated with neural tissue.

22. A deep brain stimulation and imaging probe according to claim 17, wherein the lead merges into a connector at a proximal portion thereof, the connector configured to serially interchangeably engage an MRI scanner interface and an implantable pulse generator.

23. An MRI compatible deep brain stimulation and MRI signal acquiring probe system comprising:

a flexible elongate probe body having opposing proximal and distal portions, the probe body comprising a plurality of electrodes disposed on the distal portion;

a plurality of axially extending conductors disposed in a core of the probe body, a respective one of the conductors associated with each electrode;

an axially extending inner shield surrounding the plurality of conductors for at least a major portion of the length of the conductors;

an axially extending second shield radially spaced apart above the inner shield;

an axially extending first insulating/dielectric layer disposed intermediate of the inner and second shields;

an MRI antenna member disposed at least partially on and/or in the probe body to be able to collect MRI signals at the distal portion thereof;

an RF transmit decoupling circuit in communication with the MRI antenna member; and

at least one connector attached to the proximal portion of the probe body, configured to hold a conductor transmission line for each of the electrodes.

24. A system according to claim 23, wherein the connector is configured to attach to an MRI scanner having a splitter circuit for selectively operating the electrodes or the MRI antenna member.

25. A system according to claim 23, further comprising an MRI interface that holds the RF transmit decoupler circuit, the MRI interface configured to connect the lead to an MRI scanner with the decoupler circuit decoupling the MRI antenna member during an MRI RF excitation transmission.

26. A system according to claim 23, wherein the RF transmit decoupler circuit is held in the connector.

27. A system according to claim 25, wherein the decoupler circuit comprises a matching and tuning decoupling circuit that engages an MRI scanner and decouples the electrodes.

28. A system according to claim 23, further comprising a splitter circuit in communication with the RF transmit decoupler circuit and the stimulation circuit.

29. A system according to claim 28, wherein the stimulation circuit comprises a high pass filter disposed in a transmission path intermediate a stimulation source and the electrodes.

30. A system according to claim 29, wherein the stimulation circuit is configured to block RF signals at a resonant frequency associated with a magnetic field strength of a MRI system used to operate an MRI antenna defined at least partially by the antenna member and/or probe.

31. A system according to claim 23, further comprising a splitter circuit having selective operative first and second electrical transmission paths associated with first and second operational modes, the first transmission path connecting the MRI antenna member with the MRI scanner and decoupling the electrodes during MRI operation and the second transmission path connecting the electrodes with a stimulation or recording source during electrical stimulation or recording, respectively.

32. A system according to claim 31, wherein the splitter circuit is configured to act as a high pass filter during MRI operation to electrically isolate the second transmission path from the first transmission path.

33. A system according to claim 31, wherein the splitter circuit is held in an MRI interface that is releaseably attachable to the connector.

34. A system according to claim 33, wherein the splitter circuit is held in the connector.

35. A system according to claim 27, wherein the lead is configured to serially engage with an MRI scanner and an implantable pulse generator.

36. A system according to claim 35, wherein the implantable pulse generator is MR-compatible.

37. A system according to claim 27, wherein the lead comprises at least one lumen and associated port configured to emit a therapeutic fluid to neural tissue.

38. A system according to claim 27, wherein the lead is configured to slidably enter a cannula with the connector held outside the cannula during deep brain placement.

39. A system according to claim 38, wherein the cannula is MRI-compatible.

40. A system according to claim 38, wherein the system is configured to operate with an MRI-compatible stereotactic guidance system during deep brain placement.

41. A medical kit, comprising:

an elongate sterilized biocompatible and MRI-compatible lead having opposing distal and proximal portions, the lead comprising an MRI antenna, a plurality of stimulation electrodes on the distal portion, and a plurality of axially spaced apart RF chokes disposed in a shielding layer of the lead, the lead configured to have selective operative first and second electrical transmission paths associated with at least first and second operational modes, the first transmission path connecting the MRI antenna with an MRI scanner and decoupling the electrodes during MRI operation and the second transmission path connecting the electrodes with a stimulation, ablation or recording source during electrical stimulation, ablation or recording, respectively.

42. A medical kit according to claim 41, wherein the lead is configured and sized to be chronically implantable for deep brain stimulation.

43. A medical kit according to claim 41, wherein the lead comprises a connector at the proximal end portion thereof, the connector configured to engage a chronically implantable pulse generator in the second operational mode.

44. A medical kit according to claim 41, wherein the connector is configured to be in communication with an MRI scanner in the first operational mode.

45. A medical kit according to claim 44, wherein the connector is configured to connect to an MRI interface with a splitter circuit and RF transmit decoupler circuit with the MRI interface connecting to the MRI scanner.

46. A method of placing and operating a deep brain stimulation probe, comprising:

inserting a flexible elongate lead comprising an MRI antenna and at least one stimulation electrode on a distal portion thereof into a brain of a subject;

connecting the lead to an MRI scanner interface in communication with a splitter circuit having a first electric transmission path for MRI operation and a second electric transmission path for stimulation operation;

obtaining MRI signals associated with local neural tissue proximate the MRI antenna from the MRI antenna using the first transmission path;

placing the electrode on the lead at a desired location in the brain based on the obtaining step;

then

stimulating neural tissue with the electrode using the second transmission path; and

configuring the lead to inhibit the formation and/or transmission of RF induced current,

wherein the stimulating and obtaining steps are carried out using the same lead.

47. A method according to claim 46, further comprising:

implanting the lead in the brain with the electrode held at the desired location in the brain;

connecting the lead to an implantable pulse generator; and

stimulating the neural tissue with the at least one electrode based on a stimulation signal transmitted from the implantable pulse generator to provide a therapeutic treatment.

48. A method according to claim 46, wherein the placing step comprises inserting the lead through a bore of a MRI-compatible cannula body having increased rigidity relative to the lead, the cannula body extending through the skull into neural tissue.

49. A method according to claim 46, wherein the placing step is carried out using a sterotaxis guidance system with MRI fiducial markers.

50. A method according to claim 46, wherein the obtaining step is repeated and carried out in substantially real-time to track the location of the lead in the brain.

51. A method according to claim 46, wherein the lead comprises an axially extending lumen with at least one exit port, the method further comprising releasing a therapeutic fluid into the brain.

52. A method according to claim 46, wherein the obtaining step is repeated a plurality of times before the placing step, the method further comprising recording microelectric audio signals sensed from the at least one electrode and transmitting the audio signals to an external audio device intermediate at least some of the obtaining steps.

53. A method according to claim 52, wherein the MRI antenna and at least one electrode are decoupled during RF transmission in an MRI imaging session.

54. A method according to claim 46, wherein the at least one electrode is a plurality of electrodes, at least one of which is both a recording and stimulation electrode, and wherein the MRI antenna has a viewing length of between about 1-4 cm.

55. A method according to claim 46, further comprising splitting the operation of the lead into an MRI operation and a stimulation operation, wherein the electrodes have an electrical circuit transmission path that is different during stimulation and MRI operation.

56. A method according to claim 46, wherein the at least one electrode is a plurality of electrodes, the lead having an axially extending electrical conductor held in a core for each of the electrodes, each conductor generally extending from a respective electrode to a common connector, wherein the method further comprises selectively attaching the connector to an MRI system or to an implantable pulse generator, depending on the desired operational mode.

57. A computer program product for operating a multi-purpose MRI compatible stimulation probe and MRI antenna, the computer program product comprising:

a computer readable storage medium having computer readable program code embodied in said medium, said computer-readable program code comprising;

computer readable program code that controllably engages one of a plurality of operation modes including a first or second operational mode for an MRI-compatible stimulation probe with at least one electrode and an MRI antenna, the first operational mode having a first transmission path connecting the MRI antenna with an MRI scanner and decoupling the electrodes during MRI operation and the second operational mode having a second transmission path connecting the electrodes with a stimulation or recording source during electrical stimulation or recording.

58. A computer program product according to claim 57, wherein the computer readable program code is configured to time the selection of the second operational mode to occur proximate in time but after an MRI signal acquisition by the MRI antenna in the first operational mode.

59. A computer program product according to claim 57, further comprising computer readable program code that is configured to obtain microrecordings of local tissue in substantially real time proximate in time to an MRI signal acquisition by the MRI antenna in the first operational mode.

60. A computer program product according to claim 57, further comprising computer readable program code that is configured to obtain a plurality of MRI signals of local neural tissue proximate the MRI antenna in substantially real time, then obtain a plurality of microrecordings of the local neural tissue to allow a clinician to track and/or guide placement of the probe.

61. An MRI compatible therapeutic stimulation probe comprising:

an elongate flexible probe body having an axially extending internal cavity disposed therein;

at least one electrode held by a distal portion of the probe body; and

at least one axially extending conductor configured to slidably extend into the cavity of the probe body, the at least one conductor having increased rigidity relative to the probe body,

wherein, during positioning in a body, the at least one conductor cooperates with the probe body and defines an in vivo MRI antenna used to obtain MRI signals for MRI positional guidance, and wherein, after placement, the at least one conductor can be removed from the probe body, leaving the probe body and electrode in position in the body.

62. An MRI probe according to claim 61, wherein the at least one electrode is a plurality of electrodes, at least one of which configured as a sensing and stimulation electrode.

63. An MRI probe according to claim 62, wherein the at least one conductor is a plurality of attached insulated conductors.

64. An MRI probe according to claim 61, wherein the probe body comprises a shielding layer with a plurality of axially spaced apart RF chokes.

65. An MRI probe according to claim 64, wherein the probe body comprises a first insulating layer, a first shielding layer, a second insulating layer and a second shielding layer, and wherein the RF chokes are disposed in the second shielding layer.

66. An MRI antenna and stimulation probe system, comprising:

an MRI compatible cannula having an axially extending bore; and

an elongate flexible stimulation and internal MRI signal acquisition probe having at least one electrode held by a distal portion of the probe;

wherein the stimulation and antenna probe are configured to slidably extend through the cannula bore and wherein, in operation, the cannula and antenna probe cooperate to define components of at least one deep brain MRI signal receive antenna.

67. An MRI antenna probe and stimulation probe system according to claim 66, wherein the cannula is configured to be inserted into a burr hole placed in a patient'"'"'s skull, and wherein the stimulation and MRI antenna probe are configured for deep brain placement.

68. An MRI antenna probe and stimulation probe system according to claim 66, wherein the cannula comprises a plurality of generally concentric tubular members configured to define an axially extending shield disposed over an inner conductive core, with the shield and core being insulated from each other.

69. An MRI antenna probe and stimulation probe system according to claim 66, wherein the cannula comprises a conductive shielding layer that cooperates with the stimulation and MRI antenna probe to define an MRI receive antenna during positioning to obtain MRI signals for MRI positional guidance.

70. An MRI antenna probe and stimulation probe system according to claim 69, wherein the stimulation probe is configured to remain implanted in the body.

71. An MRI antenna probe and stimulation probe system according to claim 66, wherein the stimulation and MRI antenna probe comprises a plurality of axially spaced apart RF chokes.

72. An MRI antenna probe and stimulation probe system according to claim 66, the system further comprising a controlled placement system that is configured to determine the positional location of the stimulation and antenna probe when held at a target region in the brain.