MRI COMPATIBLE ELECTRODE CIRCUIT

• US 20110046707A1
• Filed: 03/04/2010
• Published: 02/24/2011
• Est. Priority Date: 03/04/2009
• Status: Active Grant

• Current Assignee: Imricor Medical Systems, Inc.
• Original Assignee: Imricor Medical Systems, Inc.
• Inventors: Wedan, Steven R., Stenzel, Gregg S., Lloyd, Thomas W.
• Granted Patent: US 8,588,934 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 2017/00911 for fields applied by a magnetic resonance imaging system
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61N 1/086 Magnetic resonance imaging [MRI] compatible leads
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing

Abstract

An MRI compatible electrode circuit construct is provided. The construct includes at least two filter components constructed from an electrode wire. One filter component may be a resonant LC filter at or near an electrode/wire interface that resolves the issue of insufficient attenuation by effectively blocking the RF induced current on the wire from exiting the wire through the electrode. The second filter component may include one or more non-resonant filter(s) positioned along the length of the electrode wire that resolve(s) the issue of excessive heating of the resonant LC filter by significantly attenuating the current induced on the wire before it reaches the resonant LC filter. The non-resonant filter(s) may also attenuate the RF current reflected from the resonant LC filter thereby resolving the issue of the strong reflected power from the resonant filter and the associated dielectric heating.

Claims

1. A lead assembly comprising:

an elongate body having a proximal end and a distal end, said elongate body defining a lumen therewithin, the distal end arranged and configured to contact tissue and the proximal end operably coupled to an electronic control;

at least one electrode located on the elongate body; and

at least one electrical circuit in communication with said at least one electrode, said circuit housed within said elongate body and comprising one or more electrode wires, said one or more electrode wires forming at least one non-resonant filter and at least one resonant LC filter, said resonant LC filter positioned at the distal end of said elongate body proximate an electrode/wire interface.

2. The lead assembly of claim 1 wherein said at least one electrode comprises a plurality of electrodes.

3. The lead assembly of claim 1 wherein said one or more electrode wires comprises one or more single, continuous lengths of electrode wire.

4. The lead assembly of claim 1 wherein said at least one non-resonant filter is constructed from a length of electrode wire that is not continuous with a length of electrode wire used to construct said resonant LC filter.

5. The lead assembly of claim 1 wherein said one or more electrode wires comprises multiple lengths of non-continuous wire.

6. The lead assembly of claim 1 wherein said at least one non-resonant filter comprises a plurality of non-resonant filters positioned in a spaced apart relationship along a length of said electrical circuit.

7. The lead assembly of claim 1 wherein said at least one electrical circuit comprises a plurality of circuits and said at least one electrode comprises a plurality of electrodes wherein each one of said plurality of circuits is electrically coupled to a separate electrode.

8. The lead assembly of claim 1 wherein said elongate body comprises a catheter.

9. The lead assembly of claim 7 wherein said catheter is 10 French or less.

10. The lead assembly of claim 1 wherein said lead assembly is used in an implantable medical device.

11. The lead assembly of claim 1 wherein said lead assembly is used in a non-implantable medical device.

12. The lead assembly of claim 1 wherein said electrode wire comprises a circuit board trace.

13. The lead assembly of claim 1 wherein said electrode wire comprises a conductive lumen.

14. The lead assembly of claim 1 wherein said electrode wire is selected from the group consisting of copper, titanium, titanium alloys, tungsten, gold and combination of the foregoing.

15. The lead assembly of claim 1 wherein one or more electrode wires includes an insulative coating bondable by heat, chemical or adhesive means.

16. The lead assembly of claim 1 wherein said resonant LC filters effectively block RF induced current from exiting said lead assembly.

17. The lead assembly of claim 1 wherein said at least two non-resonant filters attenuate induced current on said electrode wire before said current reaches said resonant LC filter thereby avoiding excessive heating of said resonant LC filter.

18. The lead assembly of claim 1 wherein said resonant LC filter is constructed such that the inductive and capacitive characteristics resonate to create a maximal impedance at approximately 64 MHz for a 1.5 Tesla MRI.

19. The lead assembly of claim 1 wherein said resonant LC filter is constructed such that the inductive and capacitive characteristics resonate to create a maximal impedance at approximately 128 MHz for a 3.0 Tesla MRI.

20. The lead assembly of claim 1 wherein said at least one non-resonant filter is formed with approximately 45 turns of said electrode wire.

21. The lead assembly of claim 6 wherein said spaced apart relationship comprises uniform or non-uniform spacing.

22. The lead assembly of claim 8 wherein said catheter includes a catheter jacket.

23. The lead assembly of claim 22 wherein said circuit is partially or wholly embedded in said catheter jacket.

24. The lead assembly of claim 2 wherein said electrodes comprise ring electrodes.

25. The lead assembly of claim 2 wherein said electrodes comprise at least one tip electrode.

26. The lead assembly of claim 2 wherein said electrodes are positioned in a parallel relationship on either side of said elongate body.

27. The lead assembly of claim 15 wherein said insulative coating is selected from the group consisting of polyurethane, nylon, polyester, polyester-amide, polyester-imide, polyester-amide-imide and combinations of the foregoing.

28. The lead assembly of claim 1 wherein said electrical circuit is housed entirely within the lumen of said elongate body.

29. The lead assembly of claim 1 further comprising a flexible tube around which said non-resonant and resonant LC filters are helically wound.

30. The lead assembly of claim 1 wherein said at least one resonant LC filter comprises an inner layer, a middle layer and an outer layer formed from said electrode wire in a ratio of turns of approximately 3:

2;

1.

31. The lead assembly of claim 16 wherein said resonant LC filter comprises an inner layer of approximately 30 turns, a middle layer of approximately 20 turns, and an outer layer of approximately 10 turns of said electrode wire.

40. The lead assembly of claim 6 wherein said plurality of non-resonant filters comprise multiple non-resonant filters that are grouped together in a spaced apart relationship.

41. The lead assembly of claim 6 wherein said plurality of non-resonant filters create at least 1,000 or more Ohms of impedance along said electrical circuit given a lead assembly length of one meter.

44. The lead assembly of claim 1 wherein the circuit is flexible.

45. The lead assembly of claim 1 wherein the circuit is rigid.

46. The lead assembly of claims 1, 32 and 35 wherein the lead assembly is MRI compatible.

47. The lead assembly of claim 1 wherein said at least one non-resonant filter and said at least one resonant LC filter comprise discrete filters joined by multiple connecting segments of electrode wire.

32. A lead assembly comprising:

an elongate body having a proximal end and a distal end, said elongate body defining a lumen therewithin, the distal end arranged and configured to contact tissue and the proximal end operably coupled to an electronic control;

at least first and second electrodes located on the elongate body;

at least first and second electrode wires co-radially wound;

at least first and second resonant LC filters formed from said at least first and second electrode wires and in electrical communication with said first and second electrodes, said resonant LC filters positioned at the distal end of said elongate body proximate an electrode/wire interface.

33. The lead assembly of claim 32 wherein said at least first and second electrodes comprise a plurality of electrodes.

34. The lead assembly of claim 32 wherein said at least first and second electrode wires comprise a plurality of co-radially wound electrode wires.

42. The lead assembly of claim 32 wherein said circuit is flexible.

43. The lead assembly of claim 32 wherein the circuit is rigid.

35. A method of constructing a lead assembly including two or more electrical circuits for use in implantable and non-implantable medical devices comprising:

providing a first length of electrode wire to form a first electrical circuit;

helically winding said electrode wire over a length of flexible tubing from a first end of said circuit to a second end of said circuit;

forming a plurality of non-resonant filters from said electrode wire in a spaced apart relationship along said flexible tubing;

forming a most proximal first resonant LC filter;

providing a second length of electrode wire to form a second electrical circuit;

helically winding said second length of electrode wire over said length of flexible tubing from a first end of said circuit to a second end of said circuit;

forming a plurality of non-resonant filters from said second length of electrode wire in a spaced apart relationship along said flexible tubing

further helically winding said second electrode wire such that said wire passes over said most proximal resonant LC filter; and

forming a second proximal resonant LC filter distal to said most proximal first resonant LC filter.

36. The method of claim 35 further comprising providing a third length of electrode wire to form a third electrical circuit;

helically winding said third length of electrode wire over said length of flexible tubing from a first end of said circuit to a second end of said circuit;

forming a plurality of non-resonant filters from said third length of electrode wire in a spaced apart relationship along said flexible tubing

further helically winding said third electrode wire such that said wire passes over said first and second resonant LC filters; and

forming a third proximal resonant LC filter distal to said second resonant LC filters.

37. The method of claim 35 wherein said first end is a proximal end and said second end is a distal end.

38. The method of claim 35 wherein said first end is distal end and said second end is a proximal end.

39. The method of claim 35 wherein said step of forming a most proximal resonant LC filter occurs prior to said step of forming a plurality of non-resonant filters from said electrode wire in a spaced apart relationship along said flexible tubing.