BAND STOP FILTER EMPLOYING A CAPACITOR AND AN INDUCTOR TANK CIRCUIT TO ENHANCE MRI COMPATIBILITY OF ACTIVE MEDICAL DEVICES

• US 20080269591A1
• Filed: 07/10/2008
• Published: 10/30/2008
• Est. Priority Date: 06/08/2006
• Status: Active Grant

• Current Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Original Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Inventors: Stevenson, Robert A., Halperin, Henry R.
• Granted Patent: US 8,897,887 B2
• Time in Patent Office: Days
• US Class Current: 600/407
• 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: 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 33/287 involving active visualization of interventional instruments, e.g. using active tracking RF coils or coils for intentionally creating magnetic field inhomogeneities
• 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 1/0007 of radio frequency interference filters
• CPC Class Codes: H03H 2007/013 Notch or bandstop filters
• CPC Class Codes: H03H 7/1766 Parallel LC in series path H03H7/1783 takes precedence
• CPC Class Codes: Y10T 29/49169 Assembling electrical component directly to terminal or elongated conductor

Abstract

A band stop filter is provided for a lead wire of an active medical device (AMD). The band stop filter includes a capacitor in parallel with an inductor. The parallel capacitor and inductor are placed in series with the lead wire of the AMD, wherein values of capacitance and inductance are selected such that the band stop 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 band stop filter to attenuate current flow through the lead wire along a range of selected frequencies. In a preferred form, the band stop filter is integrated into a TIP and/or RING electrode for an active implantable medical device.

Claims

1. A medical diagnostic or therapeutic device, comprising:

a medical device including lead wire extending therefrom and in contact with biological cells; and

a band stop filter associated with the lead wire, for attenuating current flow through the lead wire at a selected frequency, wherein the band stop filter comprises a capacitor in parallel with an inductor, said parallel capacitor and inductor placed in series with the lead wire, wherein values of capacitance and inductance are selected such that the band stop filter is resonant at the selected frequency.

2. The device of claim 1, wherein the medical device comprises a cochlear implant, a piezoelectric sound bridge transducer, a neurostimulators, 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 stimulators, a gastric stimulators, an implantable cardioverter defibrillator, a pH probe, a congestive heart failure device, a pill camera, a neuromodulator, a cardiovascular stent, and an orthopedic implant.

3. The device of claim 1, wherein the Q of the inductor is relatively high and the Q of the capacitor is relatively low to select the overall Q of the band stop filter.

4. The device of claim 3, wherein the Q of the inductor is relatively maximized by minimizing resistive loss in the inductor.

5. The device of claim 3, wherein the Q of the capacitor is relatively minimized by raising equivalent series resistance of the capacitor.

6. The device of claim 3, wherein the overall Q of the band stop filter is reduced to attenuate current flow through the lead wire along a range of selected frequencies.

7. The device of claim 6, wherein the range of selected frequencies includes a plurality of MRI pulsed frequencies.

8. The device of claim 5, 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.

9. The device of claim 1, wherein the band stop filter is disposed adjacent to the distal tip of the lead wire.

10. The device of claim 9, wherein the band stop filter is integrated into a TIP electrode.

11. The device of claim 9, wherein the band stop filter is integrated into a RING electrode.

12. The device of claim 1, wherein the lead wire comprises an externally worn lead wire.

13. The device of claim 1, wherein the lead wire comprises an implanted lead wire.

14. The device of claim 1, wherein the medical device comprises a probe or catheter, wherein the band stop filter is associated with the probe or catheter TIP or RING electrodes, and wherein the overall Q of the band stop filter is reduced to attenuate current flow through the lead wire along a range of selected frequencies.

15-42. -42. (canceled)

43. A medical diagnostic or therapeutic device, comprising:

a medical device including a probe or catheter having TIP, RING or PAD electrodes in contact with biological cells; and

a band stop filter associated with the catheter or probe electrodes, for attenuating current flow through the probe or catheter at a selected frequency,

wherein the band stop filter comprises a capacitor in parallel with an inductor, said parallel capacitor and inductor placed in series with the probe or catheter electrode, wherein values of capacitance and inductance are selected such that the band stop filter is resonant at the selected frequency, and wherein the overall Q of the band stop filter is reduced to attenuate current flow through the lead wire along a range of selected frequencies.

44. The device of claim 43, wherein the Q of the inductor is relatively high and the Q of the capacitor is relatively low to select the overall Q of the band stop filter.

45. The device of claim 44, wherein the Q of the inductor is relatively maximized by minimizing resistive loss in the inductor.

46. The device of claim 44, wherein the Q of the capacitor is relatively minimized by raising equivalent series resistance of the capacitor.

47. The device of claim 43, wherein the range of selected frequencies includes a plurality of MRI pulsed frequencies.

48. The device of claim 46, 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.

49. A medical diagnostic or therapeutic device, comprising:

a medical device and an implantable lead wire extending therefrom and adapted to be in contact with biological cells; and

a band stop filter associated with the lead wire, for attenuating current flow through the lead wire at a selected frequency, wherein the band stop filter comprises a capacitor in parallel with an inductor, said parallel capacitor and inductor placed in series with the lead wire, wherein values of capacitance and inductance are selected such that the band stop filter is resonant along a range of selected frequencies.

50. The band stop filter of claim 49, 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 neuromodulator, a cardiovascular stent, or an orthopedic implant.

51. The band stop filter of claim 49, wherein the overall Q of the band stop filter is selected to balance impedance at a selected frequency versus frequency band width characteristics.

52. The band stop filter of claim 49, wherein the Q of the inductor is relatively high and the Q of the capacitor is relatively low to select the overall Q of the band stop filter.

53. The band stop filter of claim 52, wherein the Q of the inductor is relatively maximized by minimizing resistive loss in the inductor.

54. The band stop filter of claim 52, wherein the Q of the capacitor is relatively minimized by raising equivalent series resistance of the capacitor.

55. The band stop filter of claim 52, wherein the overall Q of the band stop filter is reduced to attenuate current flow through the lead wire along the range of selected frequencies.

56. The band stop filter of claim 55, wherein the range of selected frequencies includes a plurality of MRI pulsed frequencies.

57. The band stop filter of claim 49, wherein the band stop filter is disposed adjacent to the distal tip of the implantable lead wire.

58. The band stop filter of claim 57, wherein the band stop filter is integrated into a selected one of a TIP electrode and a RING electrode.

59. The band stop filter of claim 58, wherein the overall Q of the band stop filter is reduced to attenuate current flow through the implantable lead wire along the range of selected frequencies