Composite RF current attenuator for a medical lead

• US 9,071,221 B1
• Filed: 03/26/2015
• Issued: 06/30/2015
• Est. Priority Date: 02/04/2009
• Status: Active Grant

• Current Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Original Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Inventors: Stevenson, Robert A., Johnson, Robert Shawn, Kondabatni, Kishore Kumar, Frustaci, Dominick J., Dabney, Warren S., Moschiano, Holly Noelle, Spaulding, Joseph E.
• Primary Examiner(s): Koharski, Christopher D
• Assistant Examiner(s): Carey, Michael
• Application Number:
  US14/669,041
• Publication Number:
  US 20150207484A1
• Time in Patent Office: 96 Days
• Field of Search: 607/63, 607/115, 607/119
• US Class Current: 1/1
• 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 2018/00839 Bioelectrical parameters, e.g. ECG, EEG
• CPC Class Codes: A61B 2090/374 NMR or MRI
• CPC Class Codes: A61B 2562/182 Electrical shielding, e.g. using a Faraday cage
• CPC Class Codes: A61B 2562/222 Electrical cables or leads therefor, e.g. coaxial cables or ribbon cables
• CPC Class Codes: A61B 2562/227 Sensors with electrical connectors
• 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: 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: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents
• CPC Class Codes: H03H 1/0007 of radio frequency interference filters
• CPC Class Codes: H03H 2001/0021 Constructional details
• CPC Class Codes: H03H 2007/013 Notch or bandstop filters
• CPC Class Codes: H03H 7/0123 comprising distributed impedance elements together with lumped impedance elements

Abstract

A composite RF current attenuator for a medical lead includes a conductor having a distal electrode contactable to biological cells, a bandstop filter in series with the lead conductor for attenuating RF currents flow through the lead conductor at a selected center frequency or across a range of frequencies about the center frequency, and a lowpass filter in series with the bandstop filter and forming a portion of the lead conductor. The bandstop filter has a capacitance in parallel with a first inductance. In a preferred form, the lowpass filter includes a second inductance in series with the bandstop filter, wherein the values of capacitance and inductances for the composite RF current attenuator are selected such that it attenuates MRI-induced RF current flow in an MRI environment.

Claims

1. An implantable device, comprising:

a) at least one lead conductor having a length extending from a proximal conductor end to a distal conductor portion having a distal conductor end, wherein the proximal conductor end is electrically connectable to an active implantable medical device;

b) at least one electrode electrically connected to the distal conductor portion or the distal conductor end, wherein the electrode is contactable with biological cells; and

c) wherein the at least one lead is a coiled conductor comprising at least two portions of varying spacing between adjacent turns, the at least two portions comprising a first spacing portion having a larger spacing between adjacent turns as compared to a second spacing portion;

d) wherein the first spacing portion comprises a first inductance formed from the turns of the single coiled conductor along the first spacing portion; and

e) wherein the second spacing portion comprises a bandstop filter comprising a self-resonant inductor, wherein the self-resonant inductor comprises a second inductance formed from the turns of the single coiled conductor along the second spacing portion and

e) wherein a bandstop filter capacitance comprises parasitic capacitance formed between the adjacent turns of the coiled conductor along the second spacing portion.

2. The implantable device of claim 1, wherein the bandstop filter is configured to attenuate the MRI RF pulsed frequency at or near a center frequency or across a range of frequencies about the center frequency.

3. The implantable device of claim 2, wherein an inductance resistance and a capacitance resistance of the bandstop filter results in a 3-dB bandwidth that is at least 10 kHz so that the bandstop filter attenuates the MRI RF pulsed frequency about the center frequency.

4. The implantable device of claim 2, wherein an inductance resistance and a capacitance resistance of the bandstop filter results in a 3-dB bandwidth is at least 100 kHz so that the bandstop filter attenuates the MRI RF pulsed frequency about the center frequency.

5. The implantable device of claim 2, wherein an inductance resistance and a capacitance resistance of the bandstop filter results in a 3-dB bandwidth is at least 0.5 MHz so that the bandstop filter attenuates the MRI RF pulsed frequency about the center frequency.

6. The implantable device of claim 1, including a dielectric coating substantially surrounding the single coiled conductor along the second spacing portion.

7. The implantable device of claim 6, wherein the dielectric coating is absent substantially surrounding the single coiled conductor along the first spacing portion.

8. The implantable device of claim 1, wherein the single coiled inductor comprises a round, rectangular or square wire.

9. The implantable device of claim 1, including a hollow mandrel wherein the single coiled conductor is wrapped around the hollow mandrel.

10. The implantable device of claim 1, wherein the implantable device is an implantable lead, probe, or catheter.

11. A composite filter circuit for attenuating an MRI RF pulsed frequency in active implantable medical devices or medical leads, the composite filter circuit comprising:

a) a conductor;

b) a first inductance connected in series along the conductor; and

c) a bandstop filter connected in series along the conductor, the bandstop filter comprising a second inductance in parallel with a capacitance;

d) wherein the first inductance and bandstop filter are formed from a single coiled conductor comprising a first and second spacing between adjacent turns of the single coiled conductor;

e) wherein the first inductance is formed from the turns of the single coiled conductor along the first spacing;

f) wherein the second inductance is formed from the turns of the single coiled conductor along the second spacing;

g) wherein the capacitance comprises a parasitic capacitance between the adjacent turns of the single coiled conductor along the second spacing.

12. The composite filter circuit of claim 11, wherein the coiled conductor comprises a round, rectangular or square wire.

13. The composite filter circuit of claim 11, wherein the first spacing comprises a larger spacing between adjacent turns of the coiled conductor as compared to the second spacing.

14. The composite filter circuit of claim 11, wherein the bandstop filter attenuates the MRI RF pulsed frequency at or near a center frequency or across a range of frequencies about the center frequency.

15. The composite filter circuit of claim 11, wherein an inductance resistance and a capacitance resistance of the bandstop filter determines an overall Q of the bandstop filter, wherein the resultant 3-dB bandwidth is at least 100 kHz so that the bandstop filter attenuates the MRI RF pulsed frequency about the center frequency.

16. The composite filter circuit of claim 11, wherein an inductance resistance and a capacitance resistance of the bandstop filter determines an overall Q of the bandstop filter, wherein the resultant 3-dB bandwidth is at least 0.5 MHz so that the bandstop filter attenuates the MRI RF pulsed frequency about the center frequency.

17. The composite filter circuit of claim 11, including a dielectric coating substantially surrounding the single coiled conductor along the second spacing.

18. The composite filter circuit of claim 17, wherein the dielectric coating is absent substantially surrounding the single coiled conductor along the first spacing.

19. The composite filter circuit of claim 11, including a hollow mandrel wherein the single coiled conductor is wrapped around the hollow mandrel.