EMI FILTER EMPLOYING A CAPACITOR AND AN INDUCTOR TANK CIRCUIT HAVING OPTIMUM COMPONENT VALUES

• US 20100198312A1
• Filed: 02/17/2010
• Published: 08/05/2010
• Est. Priority Date: 04/13/2001
• Status: Active Grant

• Current Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Original Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Inventors: Moschiano, Holly Noelle, Dabney, Warren S., Stevenson, Robert A., Johnson, Robert Shawn, Halperin, Henry R.
• Granted Patent: US 8,977,355 B2
• Time in Patent Office: Days
• US Class Current: 607/63
• 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 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents
• 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: G01R 33/288 Provisions within MR facilities for enhancing safety during MR, e.g. reduction of the specific absorption rate [SAR], detection of ferromagnetic objects in the scanner room
• CPC Class Codes: H03H 1/00 Constructional details of impedance networks whose electrical mode of operation is not specified or applicable to more than one type of network constructional details of electromechanical transducers H03H9/00
• CPC Class Codes: H03H 1/0007 of radio frequency interference filters
• CPC Class Codes: H03H 2001/0092 Inductor filters, i.e. inductors whose parasitic capacitance is of relevance to consider it as filter
• CPC Class Codes: H03H 2007/013 Notch or bandstop filters
• CPC Class Codes: H03H 7/0115 comprising only inductors and capacitors H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence
• CPC Class Codes: H03H 7/1766 Parallel LC in series path H03H7/1783 takes precedence

Abstract

A bandstop filter having optimum component values is provided for a lead of an active implantable medical device (AIMD). The bandstop filter includes a capacitor in parallel with an inductor. The parallel capacitor and inductor are placed in series with the implantable lead of the AIMD, wherein values of capacitance and inductance are selected such that the bandstop filter is resonant at a selected frequency. The Q of the inductor may be relatively maximized and the Q of the capacitor may be relatively minimized to reduce the overall Q of the bandstop filter to attenuate current flow through the implantable lead along a range of selected frequencies.

Claims

1. A medical diagnostic or therapeutic device, comprising:

a medical device including a housing and a lead having a length extending between and to a proximal end adjacent to the housing and a distal end; and

a bandstop filter associated with the lead, for attenuating current flow through the lead wire at a selected frequency, wherein the bandstop filter comprises a capacitor in parallel with an inductor, said parallel capacitor and inductor placed in series with the lead somewhere along its length between and to the proximal end and the distal end, wherein values of capacitance and inductance are selected within the range of 0.1-20,000 picofarads and 1-4000 nanohenries, respectively, such that the bandstop filter is resonant at the selected frequency.

2. The device of claim 1, wherein the value of capacitance is within the range 1-100 picofarads.

3. The device of claim 1 or 2, wherein the value of inductance is within the range 100-1000 nanohenries.

4. The device of claim 3, wherein the Q of the inductor is relatively maximized and the Q of the capacitor is relatively minimized to reduce the overall Q of the bandstop filter.

5. The device of claim 4, wherein the Q of the inductor is relatively maximized by minimizing resistive loss in the inductor.

6. Device of claim 4, wherein the Q of the capacitor is relatively minimized by raising equivalent series resistance of the capacitor.

7. The device of claim 4, wherein the overall Q of the bandstop filter is reduced to attenuate current flow through the lead along a range of selected frequencies.

8. The device of claim 7, wherein the range of selected frequencies includes an MRI pulsed frequency.

9. The device of claim 6, wherein the equivalent series resistance of the capacitor is raised by any one or combination of the following:

reducing thickness of electrode plates in the capacitor;

using high resistivity capacitor electrode materials;

adding dielectric powders to electrode ink;

providing apertures, gaps, slits or spokes in the electrode plates of the capacitor;

providing separate discrete resistors in series with the capacitor;

utilizing resistive electrical attachment materials to the capacitor;

or

utilizing capacitor dielectric materials that have high dielectric loss tangents at the selected frequency.

10. The device of claim 3, wherein the bandstop filter is disposed adjacent to the distal end of the lead wire.

11. The device of claim 10, wherein the bandstop filter is integrated into a TIP electrode.

12. The device of claim 10, wherein the bandstop filter is integrated into a RING electrode.

13. The device of claim 3, including a plurality of bandstop filters associated with the lead, which resonate at different frequencies.

14. The device of claim 3, wherein the medical device comprises a cochlear implant, a piezoelectric sound bridge transducer, a neurostimulator, a brain stimulator, a cardiac pacemaker, a ventricular assist device, an artificial heart, a drug pump, a bone growth stimulator, a bone fusion stimulator, a urinary incontinence device, a pain relief spinal cord stimulator, an anti-tremor stimulator, a gastric stimulator, an implantable cardioverter defibrillator, a pH probe, a congestive heart failure device, a pill camera, a neuromodulator, a cardiovascular stent, an orthopedic implant, an external insulin pump, an external drug pump, an external neurostimulator, a Holter monitor, or an external probe or catheter.

15. The device of claim 3, wherein the medical device comprises a probe or catheter and the bandstop filter is associated with the probe or catheter TIP or RING electrodes, and wherein the overall Q of the bandstop filter is reduced to attenuate current flow through the lead along a range of selected frequencies.

16. A medical device, comprising:

an implantable lead, probe or catheter having a length extending between and to a proximal end and a distal end; and

a bandstop filter associated with the lead, probe or catheter, for attenuating current flow through the probe or catheter at a selected frequency, wherein the bandstop filter comprises a capacitor in parallel with an inductor, said parallel capacitor and inductor placed in series with the lead probe or catheter somewhere along the length between and to the proximal end and the distal end, wherein values of capacitance and inductance are selected with the range of 0.1-20,000 picofarads and 1-4000 nanohenries, respectively, such that the bandstop filter is resonant at the selected frequency, wherein the overall Q of the bandstop filter is reduced to attenuate current flow through the lead wire along a range of selected frequencies.

17. The device of claim 16, wherein the Q of the inductor is relatively maximized and the Q of the capacitor is relatively minimized to reduce the overall Q of the bandstop filter.

18. The device of claim 17, wherein the Q of the inductor is relatively maximized by minimizing resistive loss in the inductor.

19. The device of claim 17, wherein the Q of the capacitor is relatively minimized by raising equivalent series resistance of the capacitor.

20. The device of claim 16, wherein the range of selected frequencies include an MRI pulsed frequency.

21. The device of claim 19, wherein the equivalent series resistance of the capacitor is raised by any one or combination of the following:

reducing thickness of electrode plates in the capacitor;

using high resistivity capacitor electrode materials;

providing apertures, gaps, slits or spokes in the electrode plates of the capacitor;

utilizing resistive electrical attachment materials to the capacitor;

or

utilizing capacitor dielectric materials that have high dielectric loss tangents at the selected frequency.

22. The device of claim 16, including a plurality of bandstop filters associated with the lead, which resonate at different frequencies.

23. The device of claim 16, wherein the medical device comprises a cochlear implant, a piezoelectric sound bridge transducer, a neurostimulator, a brain stimulator, a cardiac pacemaker, a ventricular assist device, an artificial heart, a drug pump, a bone growth stimulator, a bone fusion stimulator, a urinary incontinence device, a pain relief spinal cord stimulator, an anti-tremor stimulator, a gastric stimulator, an implantable cardioverter defibrillator, a pH probe, a congestive heart failure device, a pill camera, a neuromodulator, a cardiovascular stent, an orthopedic implant, an external insulin pump, an external drug pump, an external neurostimulator, a Holter monitor, or an external probe or catheter.

24. The device of claim 16, wherein the value of capacitance is within the range 1-100 picofarads and the value of inductance is within the range 100-1000 nanohenries.