Band stop filter employing a capacitor and an inductor tank circuit to enhance MRI compatibility of active medical devices
First Claim
1. A lead wire system for use with an active implantable medical device, the lead wire system comprising:
- a) an implantable lead comprising at least one lead wire having a length extending to and meeting with a proximal lead end and a distal lead end;
b) a tank filter as a permanently passive circuit comprising a coiled conductor having parasitic capacitance between adjacent turns of the coiled conductor to provide a self-resonant inductor, wherein the tank filter is electrically connected in series with the lead wire somewhere along the length thereof;
c) wherein the inductor has an inductance and an inductor series resistance (RL) such that at frequencies of about 10 Hz to about 1 kHz an inductor reactance and the inductor series resistance permit passage of biological signals, and the parasitic capacitance has a capacitor series resistance (RC) such that at the frequencies of about 10 Hz to about 1 kHz a capacitor reactance and the capacitor series resistance substantially act as an open circuit to the same biological signals that the inductor permits to pass; and
d) wherein the inductor series resistance and the capacitor series resistance result in the tank filter having a Q wherein the resultant 3 db bandwidth is on the order of megahertz.
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Accused Products
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.
25 Citations
23 Claims
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1. A lead wire system for use with an active implantable medical device, the lead wire system comprising:
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a) an implantable lead comprising at least one lead wire having a length extending to and meeting with a proximal lead end and a distal lead end; b) a tank filter as a permanently passive circuit comprising a coiled conductor having parasitic capacitance between adjacent turns of the coiled conductor to provide a self-resonant inductor, wherein the tank filter is electrically connected in series with the lead wire somewhere along the length thereof; c) wherein the inductor has an inductance and an inductor series resistance (RL) such that at frequencies of about 10 Hz to about 1 kHz an inductor reactance and the inductor series resistance permit passage of biological signals, and the parasitic capacitance has a capacitor series resistance (RC) such that at the frequencies of about 10 Hz to about 1 kHz a capacitor reactance and the capacitor series resistance substantially act as an open circuit to the same biological signals that the inductor permits to pass; and d) wherein the inductor series resistance and the capacitor series resistance result in the tank filter having a Q wherein the resultant 3 db bandwidth is on the order of megahertz. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A lead wire system for use with an active implantable medical device, the lead wire system comprising:
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a) an implantable lead comprising at least one lead wire having a length extending to and meeting with a proximal lead end and a distal lead end; b) a tank filter as a permanently passive circuit comprising a coiled conductor having parasitic capacitance between adjacent turns of the coiled conductor to provide a self-resonant inductor, wherein the tank filter is electrically connected in series with the lead wire somewhere along the length thereof; c) wherein the inductor has an inductance and an inductor series resistance (RL) such that at frequencies of about 10 Hz to about 1 kHz an inductor reactance and the inductor series resistance permit passage of biological signals, and the parasitic capacitance has a capacitor series resistance (RC) such that at the frequencies of about 10 Hz to about 1 kHz a capacitor reactance and the capacitor series resistance substantially act as an open circuit to the same biological signals that the inductor permits to pass; and d) wherein an equivalent electrical circuit model of the tank filter results in an inductor in parallel with a capacitor having a Q wherein the resultant 3 db bandwidth is on the order of megahertz.
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21. An active implantable medical device lead wire system, which comprises:
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a) an implantable lead comprising at least one lead wire having a length extending to and meeting with a proximal lead end and a distal lead end; b) a tank filter as a permanently passive circuit comprising a coiled conductor having parasitic capacitance between adjacent turns of the coiled conductor to provide a self-resonant inductor, wherein the tank filter is electrically connected in series with the lead wire somewhere along the length thereof; c) wherein the inductor has an inductance and an inductor series resistance (RL) such that at low frequencies of about 10 Hz to about 1 kHz an inductor reactance and the inductor series resistance permit passage of biological signals, and the parasitic capacitance has a capacitor series resistance (RC) such that at the low frequencies of about 10 Hz to about 1 kHz a capacitor reactance and the capacitor series resistance substantially act as an open circuit to the same biological signals that the inductor segment permits to pass; d) wherein the inductor series resistance and the capacitor series resistance result in the tank filter having a Q wherein the resultant 3 db bandwidth is on the order of megahertz; and e) wherein the tank filter is electrically conductively connected between the distal end of the lead wire and an electrode, or is electrically conductively connected to the proximal end of the lead wire and electrically connectable to an external portion of a terminal pin of a hermetic seal.
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22. A lead wire system for use with an active implantable medical device, the lead wire system comprising:
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a) an implantable lead comprising at least one lead wire having a length extending to and meeting with a proximal lead end and a distal lead end; b) a tank filter as a permanently passive circuit comprising a coiled conductor having parasitic capacitance between adjacent turns of the coiled conductor to provide a self-resonant inductor, wherein the tank filter is electrically connected in series with the lead wire somewhere along the length thereof; c) wherein the inductor has an inductance and an inductor series resistance (RL) such that at low frequencies of about 10 Hz to about 1 kHz an inductor reactance and the inductor series resistance permit passage of biological signals, and the capacitor has a capacitance and a capacitor series resistance (RC) such that at the low frequencies of about 10 Hz to about 1 kHz a capacitor reactance and the capacitor series resistance substantially act as an open circuit to the same biological signals that the inductor permits to pass; and d) wherein the inductor series resistance and the capacitor series resistance result in the tank filter being tuned to a resonant center frequency and having a 3 db bandwidth in the megahertz frequency range. - View Dependent Claims (23)
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Specification