Band stop filter employing a capacitor and an inductor tank circuit to enhance MRI compatibility of active medical devices
First Claim
1. A process for attenuating current flow through an active implantable medical device lead wire system, the lead wire system comprising a tank filter and a lead wire having a length extending to and meeting with a proximal lead wire end and a distal lead wire end with the lead wire system being completely external to a housing for the medical device, comprising the steps of:
- a) forming the tank filter as a permanently active circuit, the tank filter comprising a capacitor segment having a capacitor segment first end and a capacitor segment second end, and an inductor segment having an inductor segment first end and an inductor segment second end, by electrically connecting the capacitor segment first end to the inductor segment first end, and electrically connecting the capacitor segment second end to the inductor segment second end so that the inductor and the capacitor are electrically coupled to one another in parallel;
b) electrically connecting the tank filter circuit in series with the lead wire somewhere along the length thereof;
c) wherein the inductor segment has an inductor segment inductance and an inductor segment series resistance (RL), wherein at low frequencies of about 10 Hz to about 1 kHz an inductor segment reactance and the inductor segment series resistance permit passage of biological signals, and the capacitor segment has a capacitor segment capacitance and a capacitor segment series resistance (Rc), wherein at low frequencies of about 10 Hz to about 1 kHz a capacitor segment reactance and the capacitor segment series resistance substantially act as an open circuit to the same biological signals that the inductor segment is allowing to pass; and
d) wherein the inductor segment resistance, the inductor segment inductance, the capacitor segment capacitance, and the capacitor segment resistance result in the tank filter having a Q wherein the resultant 3 dB bandwidth in 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.
84 Citations
67 Claims
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1. A process for attenuating current flow through an active implantable medical device lead wire system, the lead wire system comprising a tank filter and a lead wire having a length extending to and meeting with a proximal lead wire end and a distal lead wire end with the lead wire system being completely external to a housing for the medical device, comprising the steps of:
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a) forming the tank filter as a permanently active circuit, the tank filter comprising a capacitor segment having a capacitor segment first end and a capacitor segment second end, and an inductor segment having an inductor segment first end and an inductor segment second end, by electrically connecting the capacitor segment first end to the inductor segment first end, and electrically connecting the capacitor segment second end to the inductor segment second end so that the inductor and the capacitor are electrically coupled to one another in parallel; b) electrically connecting the tank filter circuit in series with the lead wire somewhere along the length thereof; c) wherein the inductor segment has an inductor segment inductance and an inductor segment series resistance (RL), wherein at low frequencies of about 10 Hz to about 1 kHz an inductor segment reactance and the inductor segment series resistance permit passage of biological signals, and the capacitor segment has a capacitor segment capacitance and a capacitor segment series resistance (Rc), wherein at low frequencies of about 10 Hz to about 1 kHz a capacitor segment reactance and the capacitor segment series resistance substantially act as an open circuit to the same biological signals that the inductor segment is allowing to pass; and d) wherein the inductor segment resistance, the inductor segment inductance, the capacitor segment capacitance, and the capacitor segment resistance result in the tank filter having a Q wherein the resultant 3 dB bandwidth in on the order of megahertz. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 62, 63, 64, 65, 66, 67)
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10. A process for attenuating current flow through an active implantable medical device lead wire system, the lead wire system comprising a tank filter and a lead wire having a length extending to and meeting with a proximal lead wire end and a distal lead wire end with the lead wire system being completely external to a housing for the medical device, comprising the steps of:
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a) forming the tank filter as a permanently active circuit, the tank filter comprising a capacitor segment having a capacitor segment first end and a capacitor segment second end, and an inductor segment having an inductor segment first end and an inductor segment second end, by electrically connecting the capacitor segment first end to the inductor segment first end, and electrically connecting the capacitor segment second end to the inductor segment second end so that the inductor and the capacitor are electrically coupled to one another in parallel; electrically connecting the tank filter circuit in series with the lead wire somewhere along the length thereof; wherein the inductor segment has an inductor segment inductance and an inductor segment series resistance (RL), wherein at low frequencies of about 10 Hz to about 1 kHz an inductor segment reactance and the inductor segment series resistance permit passage of biological signals, and the capacitor segment has a capacitor segment capacitance and a capacitor segment series resistance (Rc), wherein at low frequencies of about 10 Hz to about 1 kHz a capacitor segment reactance and the capacitor segment series resistance substantially act as an open circuit to the same biological signals that the inductor segment is allowing to pass; d) wherein the inductor segment series resistance, the inductor segment inductance, the capacitor segment capacitance, and the capacitor segment series resistance result in the tank filter having a Q wherein the resultant 3 dB bandwidth is in the megahertz range; and e) implanting the medical device in a body with an electrode at the distal end of the lead wire contacting body tissue such that low frequency biological sensing and stimulating signals carried by the lead wire must pass through the tank filter circuit. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 32)
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33. A process for attenuating current flow through an active implantable medical device lead wire system, the lead wire system comprising a tank filter and a lead wire having a length extending to and meeting with a proximal lead wire end and a distal lead wire end with the lead wire system being completely external to a housing for the medical device, comprising the steps of:
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a) forming the tank filter as a permanently active circuit, the tank filter comprising a capacitor segment having a capacitor segment first end and a capacitor segment second end, and an inductor segment having an inductor segment first end and an inductor segment second end, by electrically connecting the capacitor segment first end to the inductor segment first end, and electrically connecting the capacitor segment. second end to the inductor segment second end so that the inductor and the capacitor are electrically coupled to one another in parallel; b) wherein the inductor segment has an inductor segment inductance and an inductor segment series resistance (RL), wherein at low frequencies of about 10 Hz to about 1 kHz an inductor segment reactance and the inductor segment series resistance permit passage of biological signals, and the capacitor segment has a capacitor segment capacitance and a capacitor segment series resistance (Rc), wherein at low frequencies of about 10 Hz to about 1 kHz a capacitor segment reactance and the capacitor segment series resistance substantially act as an open circuit to the same biological signals that the inductor segment is allowing to pass; c) wherein the inductor segment series resistance, the inductor segment inductance, the capacitor segment capacitance, and the capacitor segment series resistance result in the tank filter having a Q wherein the resultant 3 dB bandwidth is in the megahertz range; and d) electrically connecting the tank filter in series with the lead wire, wherein the capacitor segment first end and the inductor segment first end are electrically connected to the distal end of the lead wire and the capacitor segment second end and the inductor segment second end are electrically coupled to an electrode. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46)
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47. A process for attenuating current flow through an active implantable medical device lead wire system, the lead wire system comprising a tank filter and a lead wire having a length extending to and meeting with a proximal end and a distal end with the lead wire system being completely external to a housing for the medical device, comprising the steps of
a) forming the tank filter as a permanently active circuit, the tank filter comprising a capacitor segment having a capacitor segment first end and a capacitor segment second end, and an inductor segment having an inductor segment first end and an inductor segment second end, by electrically connecting the capacitor segment first end to the inductor segment first end, and electrically connecting the capacitor segment second end to the inductor segment second end; -
b) wherein the inductor segment has an inductor segment inductance and an inductor segment series resistance (RL), wherein at low frequencies of about 10 Hz to about 1 kHz an inductor segment reactance and the inductor segment series resistance permit passage of biological signals, and the capacitor segment has a capacitor segment capacitance and a capacitor segment series resistance (Rc), wherein at low frequencies of about 10 Hz to about 1 kHz a capacitor segment reactance and the capacitor segment series resistance substantially act as an open circuit to the same biological signals that the inductor segment is allowing to pass; wherein the inductor segment series resistance, the inductor segment inductance, the capacitor segment capacitance, and the capacitor segment series resistance result in the tank filter having a Q wherein the resultant 3 dB bandwidth is in the megahertz range; and d) electrically connecting the tank filter in series with the lead wire, wherein the capacitor segment first end and the inductor segment first end are electrically connected to an external portion of a terminal pin of a hermetic seal and the capacitor segment second end and the inductor segment second end are electrically coupled to the proximal end of the lead wire. - View Dependent Claims (48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61)
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Specification