EMI filter employing a capacitor and an inductor tank circuit having optimum component values

摘要

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.

主权项

1. An implantable lead wire, comprising:
a) a length extending from a proximal lead wire end to a distal lead wire portion having a distal lead wire end, wherein the proximal lead wire end is electrically connectable to electronic circuits of an implantable medical device; b) an electrode electrically connected to the distal lead wire portion or to the distal lead wire end, wherein the electrode is contactable to biological tissue; and c) at least one bandstop filter comprising a capacitor segment having a capacitor segment first end spaced from a capacitor segment second end and an inductor segment having an inductor segment first end spaced from an inductor segment second end, wherein the capacitor and inductor segment first ends are electrically connected together at a first connection along the lead wire length and the capacitor and inductor segment second ends are electrically connected together at a second connection along the lead wire so that the parallel connected capacitor and inductor segments as a permanently passive circuit forming the at least one bandstop filter are physically and electrically connected in series with the lead wire somewhere along the length thereof, d) wherein the inductor segment has an inductance ranging from 1 to 4,000 nanohenries and an inductor segment series resistance (RL) so that an inductor segment reactance and the inductor segment series resistance permit passage of biological signals at frequencies of about 10 Hz to about 1 kHz along the lead wire from the electrode to the proximal lead wire end, and e) wherein the capacitor segment has a capacitance ranging from 0.1 to 20,000 picofarads and a capacitor segment series resistance (RC) so that a capacitor segment reactance and the capacitor segment series resistance substantially act as an open circuit to the same biological signals at frequencies of about 10 Hz to about 1 kHz that the inductor segment allows to pass along the lead wire, and f) wherein the capacitance, the capacitor segment series resistance, the inductance and the inductor segment series resistance result in the at least one bandstop filter having a Q with a 3-dB bandwidth that is on the order of MHz substantially centered at an MRI RF pulsed resonant frequency.