SWITCHED SAFETY PROTECTION CIRCUIT FOR AN AIMD SYSTEM DURING EXPOSURE TO HIGH POWER ELECTROMAGNETIC FIELDS

• US 20100208397A1
• Filed: 03/25/2010
• Published: 08/19/2010
• Est. Priority Date: 12/17/2008
• Status: Active Grant

• Current Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Original Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Inventors: Dabney, Warren S., Stevenson, Robert A., Moschiano, Holly Noelle, Brainard, Scott, Johnson, Robert Shawn, Williams, Christopher Michael
• Granted Patent: US 8,447,414 B2
• Time in Patent Office: Days
• US Class Current: 361/54
• CPC Class Codes: A61B 2017/00911 for fields applied by a magnetic resonance imaging system
• CPC Class Codes: A61B 2018/00839 Bioelectrical parameters, e.g. ECG, EEG
• 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: A61N 1/37512 Pacemakers
• 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: H03H 7/0107 Non-linear filters
• CPC Class Codes: H03H 7/1758 Series LC in shunt or branch path H03H7/1791 takes precedence
• CPC Class Codes: H03H 7/1766 Parallel LC in series path H03H7/1783 takes precedence

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 disposed between the diversion circuit and the AIMD electronics for diverting energy in the implanted lead or the leadwire 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 safety protection circuit for an AIMD system during exposure to high power electromagnetic fields, comprising:

an active implantable medical device (AIMD) including AIMD electronics;

an implanted lead or a leadwire associated with the AIMD electronics;

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 in the implanted lead or the leadwire associated with the AIMD electronics.

2. The switched safety protection circuit of claim 1, wherein the diversion circuit is permanently conductively connected between the implanted lead or the leadwire and the energy dissipating surface.

3. The switched safety protection circuit of claim 1, including a switch associated with the diversion circuit and disposed between the lead or the leadwire and the energy dissipating surface.

4. The switched safety protection circuit of claim 3, wherein the switch associated with the diversion circuit is disposed between the implanted lead or the leadwire and the diversion circuit.

5. The switched safety protection circuit of claim 3, wherein the switch associated with the diversion circuit is disposed between the diversion circuit and the energy dissipating surface.

6. The switched safety protection circuit of claims 4 or 5, wherein the switch associated with the diversion circuit comprises a single or multi-pole single or multi-throw switch.

7. The switched safety protection circuit of claims 4 or 5, wherein the switch associated with the diversion circuit 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 safety protection 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, and simultaneously conductively couples the AIMD electronics to the energy dissipating surface.

9. The switched safety protection circuit of claim 8, wherein the switch comprises a single or multi-pole, double-throw switch.

10. The switched safety protection circuit of claim 1, wherein the AIMD electronics include non-linear circuit elements, over-voltage circuit elements, transient voltage suppression diodes, Transorbs, AIMD sensing circuits and therapy delivery circuits.

11. The switched safety protection 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.

12. The switched safety protection circuit of claim 11, wherein the selected RF frequency or frequency band comprises an MRI frequency.

13. The switched safety protection circuit of claim 12, wherein said MRI frequency comprises a range of MRI frequencies.

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

15. The switched safety protection circuit of claim 14, wherein the diversion circuit has a capacitive reactance generally equal and opposite to the characteristic inductive reactance of the implanted lead.

16. The switched safety protection circuit of claim 11, wherein the capacitive reactance and the inductive reactance each have a resistor component.

17. The switched safety protection circuit of claims 1 or 11, wherein the diversion circuit comprises a low pass filter.

18. The switched safety protection circuit of claim 17, wherein the low pass filter comprises a capacitor, an inductor, a Pi filter, a T filter, an LL filter, or an “

n”

element filter

19. The switched safety protection circuit of claim 18, wherein said diversion circuit comprises a unipolar or multipolar feedthrough capacitor.

20. The switched safety protection circuit of claims 1 or 11, wherein the diversion circuit comprises at least one series resonant L-C trap filter.

21. The switched safety protection circuit of claim 20, wherein the diversion circuit comprises a plurality of L-C trap filters resonant respectively at different MRI frequencies.

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

23. The switched safety protection circuit of claim 22, 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.

24. The switched safety protection circuit of claim 22, wherein said diversion circuit is disposed within said housing.

25. The switched safety protection circuit of claim 22, wherein the diversion circuit comprises a short to the housing.

26. The switched safety protection circuit of claim 22, wherein the diversion circuit is disposed within a header block for the AIMD.

27. The switched safety protection circuit of claim 22, including an EMI shield conductively coupled to the housing and coaxially extending about the lead or the leadwire in non-conductive relation.

28. The switched safety protection circuit of claim 27, wherein the diversion circuit is conductively coupled to the EMI shield.

29. The switched safety protection circuit of claims 1, 11 or 22, wherein the diversion circuit comprises a high pass filter.

30. The switched safety protection circuit of claim 29, 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.

31. The switched safety protection circuit of claim 29, wherein the high pass filter comprises a capacitor.

32. The switched safety protection circuit of claim 31, wherein the high pass filter comprises a resistor in series with a capacitor.

33. The switched safety protection circuit of claim 29, wherein the high pass filter comprises an LC trap filter.

34. The switched safety protection 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.

35. The switched safety protection circuit of claim 34, wherein the diversion circuit is disposed at or adjacent to the proximal end of the implanted lead.

36. The switched safety protection circuit of claim 35, wherein the diversion circuit is disposed in a proximal lead connector.

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

38. The switched safety protection circuit of claim 37, wherein the impeding circuit comprises an inductor.

39. The switched safety protection circuit of claim 37, wherein the impeding circuit comprises a bandstop filter.

40. The switched safety protection circuit of claims 38 or 39, wherein the diversion circuit comprises a resistor.

41. The switched safety protection circuit of claims 38 or 39, wherein the diversion circuit comprises a low pass filter.

42. The switched safety protection circuit of claim 41, wherein the low pass filter comprises a capacitor, an inductor, a Pi filter, a T filter, an LL filter, or an “

n”

element filter.

43. The switched safety protection circuit of claims 38 or 39, wherein the diversion circuit comprises at least one series resonant L-C trap filter.

44. The switched safety protection circuit of claim 43, wherein the diversion circuit comprises a plurality of L-C trap filters resonant respectively at different MRI frequencies.

45. The switched safety protection circuit of claim 41, wherein the diversion circuit comprises a resistor.

46. The switched safety protection circuit of claim 43, wherein the diversion circuit comprises a resistor.

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

48. The switched safety protection circuit of claim 47, wherein the energy dissipating surface comprises at least a portion of a handle for a probe or catheter.

49. The switched safety protection 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.

50. The switched safety protection circuit of claim 49, wherein said diversion circuit couples each of said leads to the energy dissipating surface.

51. The switched safety protection circuit of claims 49 or 50, wherein said diversion circuit is coupled between said pair of leads.

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

53. The switched safety protection circuit of claim 1, wherein the energy dissipating surface includes a biomimetic coating.

54. The switched safety protection circuit of claim 1, wherein the diversion circuit includes at least one non-linear circuit element.

55. The switched safety protection circuit of claim 54, wherein the at least one non-linear circuit element comprises a transient voltage suppressor.

56. The switched safety protection circuit of claim 54, wherein the at least one non-linear circuit element comprises a diode.