Medical lead having a bandstop filter employing a capacitor and an inductor tank circuit to enhance mri compatibility

Abstract

A bandstop filter includes a capacitance in parallel with an inductance and is placed in series with the implantable lead of an active implantable medical device, wherein values of capacitance and inductance are selected such that the bandstop filter attenuates RF current flow at a selected center MRI RF pulsed frequency or across a range of frequencies. The Q i of the inductor and the Q c of the capacitor are controlled to reduce the overall Q of the bandstop filter to attenuate current flow through the implantable lead along a range of selected frequencies. In a preferred form, the bandstop filter is integrated into a Tip and/or Ring electrode for the active implantable medical device.

What is claimed is: 
     
         1 . An implantable medical lead, comprising:
 a conductor having a length extending between and to a proximal end and a distal end; and   at least one bandstop filter comprising a capacitance in parallel with an inductance, said parallel capacitance and inductance placed in series with the conductor somewhere along the length of the conductor between the proximal end and the distal end;   wherein values of capacitance and inductance have been selected such that the bandstop filter attenuates RF current flow at a selected center MRI RF pulsed frequency or across a range of frequencies;   wherein the inductance is inherently derived from the lead's material of construction or structure; and   wherein the capacitance is inherently derived from the lead's material of construction or structure.   
     
     
         2 . The lead of  claim 1 , wherein the capacitance comprises parasitic capacitance. 
     
     
         3 . The lead of  claim 1 , wherein the bandstop filter comprises at least a part of a coiled or spiral inductor portion of the lead, and the capacitance comprises parasitic capacitance between adjacent turns of said inductor portion. 
     
     
         4 . The lead of  claim 3 , wherein the overall Q of the bandstop filter is selected to balance impedance at the selected frequency versus frequency band width characteristics. 
     
     
         5 . The lead of  claim 1 , wherein the bandstop filter is integrated into a selected one of a Tip electrode or a Ring electrode. 
     
     
         6 . The lead of  claim 3 , wherein a Q i  of the inductance is relatively high and a Q c  of the capacitance is relatively low to select the overall Q of the bandstop filter. 
     
     
         7 . The lead of  claim 1 , wherein the inductance has a relatively low resistive loss, and wherein the capacitance has a relatively high equivalent series resistance. 
     
     
         8 . The lead of  claim 7 , wherein the Q i  of the inductance is relatively high by lowering resistive loss in the inductance. 
     
     
         9 . The lead of  claim 7 , wherein the Q c  of the capacitance is relatively lowered by raising equivalent series resistance of the capacitance. 
     
     
         10 . The lead of  claim 3 , wherein a Q of the inductance element and a Q c  of the capacitance element are selected such that the overall Q of the bandstop filter attenuates current flow through the lead at the selected center frequency or across the range of frequencies. 
     
     
         11 . The lead of  claim 3 , wherein the overall Q of the bandstop filter is lowered to attenuate current flow through the lead across a range of selected frequencies. 
     
     
         12 . The lead of  claim 1 , wherein the AIMD a comprises cochlear implant, a piezoelectric sound bridge transducer, a neurostimulator, a brain stimulator, a cardiac pacemaker, a ventricular assist device, an artificial heart, a drug pump, a bone growth stimulator, a bone fusion stimulator, a urinary incontinence device, a pain relief spinal cord stimulator, an anti-tremor stimulator, a gastric stimulator, an implantable cardioverter defibrillator, a pH probe, a congestive heart failure device, a neuromodulator, or a cardiovascular stent. 
     
     
         13 . An implantable medical lead, comprising:
 at least one a bandstop filter comprising at least a portion of the lead, for attenuating RF current flow through the lead at a selected center frequency or across a range of frequencies, wherein the bandstop filter comprises a capacitance in parallel with an inductance, wherein values of capacitance and inductance are selected such that the bandstop filter attenuates RF current flow at the selected center frequency or across the range of frequencies;   wherein the bandstop filter comprises at least a part of a coiled or spiral inductor portion of the lead, and the capacitance comprises parasitic capacitance between adjacent turns of said inductor portion.   
     
     
         14 . The lead of  claim 13 , wherein the overall Q of the bandstop filter is selected to balance impedance at the selected frequency versus frequency band width characteristics. 
     
     
         15 . The lead of  claim 13 , wherein a Q i  of the inductance is relatively high and a Q c  of the capacitance is relatively low to reduce the overall Q of the bandstop filter. 
     
     
         16 . The lead of  claim 15 , wherein the Q i  of the inductance is relatively high by lowering resistive loss in the inductance. 
     
     
         17 . The lead of  claim 15 , wherein the Q c  of the capacitance is relatively lowered by raising equivalent series resistance of the capacitance. 
     
     
         18 . The lead of  claim 13 , wherein a Q of the inductance element a Q c  of the capacitance element are selected such that the overall Q of the bandstop filter attenuates current flow through the lead at the selected center frequency or across the range of frequencies. 
     
     
         19 . The lead of  claim 18 , wherein the range of frequencies includes a plurality of MRI RF pulsed frequencies. 
     
     
         20 . The lead of  claim 13 , wherein the bandstop filter is disposed at, within or adjacent to a distal Tip electrode. 
     
     
         21 . The lead of  claim 13 , wherein the bandstop filter is integrated into a selected one of a Tip electrode or a Ring electrode. 
     
     
         22 . The lead of  claim 13 , wherein the overall Q of the bandstop filter is lowered to attenuate current flow through the lead across the range of frequencies. 
     
     
         23 . The lead of  claim 13 , wherein a Q i  of the inductance is relatively low and a Q c  of the capacitance is relatively high to reduce the overall Q of the bandstop filter.