Implantable lead bandstop filter employing an inductive coil with parasitic capacitance to enhance MRI compatibility of active medical devices

摘要

A medical lead system includes at least one bandstop filter for attenuating current flow through the lead across a range of frequencies. The bandstop filter has an overall circuit Q wherein the resultant 3 dB bandwidth is at least 10 kHz. The values of capacitance and inductance of the bandstop filter are selected such that the bandstop filter is resonant at a selected center frequency or range of frequencies. Preferably, the bandstop filter has an overall circuit Q wherein the resultant 10 dB bandwidth is at least 10 kHz. Such bandstop filters are backwards compatible with known implantable deployment systems and extraction systems.

主权项

1. An implantable medical lead, comprising:
a) an implantable lead conductor 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) a mandrel comprising an intermediate mandrel body extending from a proximal mandrel end cap to a distal mandrel end cap, wherein the proximal and distal mandrel ends are electrically conductive; c) a self-resonant inductor comprising at least a portion of the lead conductor formed as a coiled inductor contacted with a dielectric material, wherein the coiled inductor contacted with the dielectric material is wrapped around the mandrel body from adjacent to the proximal mandrel end cap to adjacent to the distal mandrel end cap; d) 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 e) an insulation material extending from at least a first outer surface of the proximal mandrel end cap to a second outer surface of the distal mandrel end cap and covering at least an outer surface of the dielectric material contacting the coiled inductor to thereby prevent RF currents in body fluids and tissues from flowing from and to the proximal and distal mandrel ends by isolating both ends of the self-resonant inductor, which currents would otherwise degrade an impedance at resonance of the self-resonant inductor, f) wherein the self-resonant inductor has a parasitic capacitance between adjacent turns of the coiled inductor to thereby provide an equivalent circuit comprising an inductance in parallel with the parasitic capacitance, g) wherein the parasitic capacitance provides a capacitive series resistance (RC) and the self-resonant inductor has an inductance and an inductor series resistance (RL), wherein at low frequencies of about 10 Hz to about 1 kHz an inductive reactance and the inductor series resistance (RL) permit passage of biological signals from the electrode to the proximal lead conductor end while a capacitive reactance and the capacitive series resistance (RC) substantially act as an open circuit to the same biological signals that the self-resonant inductor allows to pass, h) wherein the self-resonant inductor is resonant at or near an RF frequency, thereby providing a high impedance in series with the lead conductor at or near the RF frequency, and i) wherein the self-resonant inductor has an overall circuit Q so that the resultant 3-dB bandwidth is at least 100 kHz.