PROCESS FOR TUNING AN EMI FILTER TO REDUCE THE AMOUNT OF HEAT GENERATED IN IMPLANTED LEAD WIRES DURING MEDICAL PROCEDURES SUCH AS MAGNETIC RESONANCE IMAGING
First Claim
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1. A process for tuning an EMI filter for an active implantable medical device (AIMD), the EMI filter having a capacitor and an inductor/resistor element, comprising the steps of:
- evaluating input impedance of the AIMD;
configuring the physical relationship of the capacitor and the inductor/resistor element of the EMI filter, based on the evaluated input impedance of the AIMD;
iteratively selecting component values for the capacitor and inductor/resistor elements of the EMI filter; and
analyzing the impedance characteristics of the selected components through circuit simulation to assess (a) whether the impedance of the EMI filter has been raised sufficiently to reduce undesirable RF currents that would flow during medical diagnostic procedures, and (b) if the AMID is adequately protected against environmental emitters and complies with regulatory requirements.
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Abstract
In EMI filter assemblies incorporating one or more passive filter elements including feedthrough capacitors and lossy ferrite inductors, a process is provided for tuning the various components to reduce the amount of heat generated in implanted lead wires during medical procedures such as magnetic resonance imaging. The process includes selection and testing of individual components and an interative process involving tradeoffs and subsequent testing prior to finalization of the feedthrough design.
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Citations
25 Claims
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1. A process for tuning an EMI filter for an active implantable medical device (AIMD), the EMI filter having a capacitor and an inductor/resistor element, comprising the steps of:
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evaluating input impedance of the AIMD;
configuring the physical relationship of the capacitor and the inductor/resistor element of the EMI filter, based on the evaluated input impedance of the AIMD;
iteratively selecting component values for the capacitor and inductor/resistor elements of the EMI filter; and
analyzing the impedance characteristics of the selected components through circuit simulation to assess (a) whether the impedance of the EMI filter has been raised sufficiently to reduce undesirable RF currents that would flow during medical diagnostic procedures, and (b) if the AMID is adequately protected against environmental emitters and complies with regulatory requirements. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A process for tuning an EMI filter for an active implantable medical device (AIMD), the EMI filter having a capacitor and an inductor/resistor element, comprising the steps of:
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evaluating input impedance of the AIMD;
configuring the physical relationship of the capacitor and the inductor/resistor element of the EMI filter, based on the evaluated input impedance of the AIMD, by utilizing an inductive/resistive element located at a point of lead wire ingress and egress from the AIMD followed by the capacitor, where the capacitance value of said capacitor is minimized to reduce RF currents in a lead wire system of the AIMD;
iteratively selecting component values for the capacitor and inductor/elements of the EMI filter;
analyzing the impedance characteristics of the selected components through circuit simulation to assess (a) whether the impedance of the EMI filter has been raised sufficiently to reduce undesirable RF currents that would flow during medical diagnostic procedures, and (b) if the AMID is adequately protected against environmental emitters and complies with regulatory requirements;
building a prototype of the AIMD comprising an EMI filter having selected components that have been assessed to be acceptable;
testing the prototype to determine whether the impedance of the EMI filter has been raised sufficiently to reduce undesirable currents that would flow during medical diagnostic procedures; and
testing the prototype to determine if the AMID is adequately protected against environmental emitters and complies with regulatory requirements. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification