MRI-safe high impedance lead systems
View Patent ↗Some embodiments are directed to MRI/RF compatible medical interventional devices. A plurality of spaced apart high impedance circuit segments are configured to have a high impedance at a high range of radiofrequencies and a low impedance at a low range of frequencies. The high impedance circuit segments may comprise co-wound coiled inductors and can reduce, block or inhibit RJ-transmission along the lead system ( 20 ) during exposure to RF associated with a high-Held magnet MRI systems, while permuting passage of low frequency physiologic signals, treatments and/or stimuli. The devices can include at least one electrode.
1. An MRI safe lead, comprising:
an elongate flexible body, the body having distal and proximal portions;
a plurality of conductors extending along the flexible body, each conductor comprising a plurality of axially spaced-apart coiled segments and a plurality of linear segments residing between adjacent coiled segments;
at least one electrode disposed along the distal portion of the body and coupled to the plurality of conductors;
a dielectric disposed over the conductors;
a conductive shield disposed over the dielectric with the dielectric residing between the conductors and the conductive shield; and
a plurality of first capacitors, each first capacitor electrically connecting a respective one of the conductors to the shield to define a RF short and low frequency open circuit,
wherein the coiled segments of the conductors, the dielectric, the conductive shield, and the plurality of capacitors define a plurality of high impedance segments that are tuned to a target RF frequency associated with an MR 1 system.
2. The lead of claim 1 , wherein each of the plurality of first capacitors is coupled to the respective one of the conductors before a proximal end of one of the coiled segments of the respective one of the conductors.
3. The lead of claim 2 , further comprising a plurality of second capacitors, each second capacitor coupled to a respective one of the conductors after a distal end of one of the coiled segments of the respective one of the conductors.
4. The lead of claim 3 , wherein the second capacitors are tuning capacitors.
5. The lead of claim 1 , wherein the target RF frequency is in a range from 1MHz to 250 MHz.
6. The lead of claim 1 , wherein the high impedance segments are positioned along the conductors so that adjacent high impedance segments are separated by a distance of less than one quarter of a wavelength of the target RF frequency.
7. The lead of claim 1 , wherein at least some of the coiled segments of different conductors are co-wound together.
8. An MRI safe lead, comprising:
an elongate flexible body, the body having distal and proximal portions;
a plurality of conductors extending along the flexible body, each conductor comprising a plurality of axially spaced-apart coiled segments and a plurality of linear segments residing between adjacent coiled segments;
at least one electrode disposed along the distal portion of the body and coupled to the plurality of conductors;
a dielectric disposed over the conductors;
a conductive shield disposed over the dielectric with the dielectric residing between the conductors and the conductive shield; and
a plurality of first capacitors, each first capacitor electrically connecting a respective one of the conductors to the shield,
wherein the coiled segments of the conductors, the dielectric, the conductive shield, and the plurality of capacitors define a plurality of RF traps that are tuned to a target RF frequency associated with an MRI system.
9. The lead of claim 8 , wherein each of the plurality of first capacitors is coupled to the respective one of the conductors before a proximal end of one of the coiled segments of the respective one of the conductors.
10. The lead of claim 9 , further comprising a plurality of second capacitors, each second capacitor coupled to a respective one of the conductors after a distal end of one of the coiled segments of the respective one of the conductors.
11. The lead of claim 10 , wherein the second capacitors are tuning capacitors.
12. The lead of claim 8 , wherein the target RF frequency is in a range from 1MHz to 250 MHz.
13. The lead of claim 8 , wherein the high impedance segments are positioned along the conductors so that adjacent high impedance segments are separated by a distance of less than one quarter of a wavelength of the target RF frequency.
14. The lead of claim 8 , wherein at least some of the coiled segments of different conductors are co-wound together.
15. An MRI safe lead, comprising:
an elongate flexible body, the body having distal and proximal portions;
a plurality of conductors extending along the flexible body, each conductor comprising a plurality of axially spaced-apart coiled segments and a plurality of linear segments residing between adjacent coiled segments, wherein the conductors form a plurality of cowound arrangements, each arrangement comprises one of the coiled segments of each conductor axially cowound together;
at least one electrode disposed along the distal portion of the body and coupled to the plurality of conductors;
a dielectric disposed over the conductors; and
a conductive shield disposed over the dielectric with the dielectric residing between the conductors and the conductive shield;
wherein the coiled segments of the conductors are electrically coupled to the conductive shield.
16. The lead of claim 15 , further comprising a plurality of first capacitors, each first capacitor electrically connecting a respective one of the conductors to the shield to define a RF short and low frequency open circuit.
17. The lead of claim 16 , wherein each of the plurality of first capacitors is coupled to the respective one of the conductors before a proximal end of one of the coiled segments of the respective one of the conductors.
18. The lead of claim 17 , further comprising a plurality of second capacitors, each second capacitor coupled to a respective one of the conductors after a distal end of one of the coiled segments of the respective one of the conductors.
19. The lead of claim 15 , wherein the coiled segments of the conductors, the dielectric, and the conductive shield define a plurality of RF traps that are tuned to a target RF frequency associated with an MRI system.
20. The lead of claim 15 , wherein the coiled segments of the conductors, the dielectric, and the conductive shield define a plurality of high impedance segments that are tuned to a target RF frequency associated with an MRI system.