Segmented MRI catheters and other interventional devices
Disclosed herein are segmented MRI-compatible interventional devices, such as catheters and guidewires, that provide desired mechanical properties while avoiding undesired interactions with MRI fields. Disclosed devices can include helical wires with insulated breaks at intervals along each wire so that the insulated wire segments are individually short enough to avoid substantial resonance and heat being generated in the wires due to an applied MRI field. The segmented wires can be organized into a braided/woven tubular configuration or a non-braided intercalated/parallel tubular configuration that provides the desired mechanical properties similar to conventional metallic braided catheters. The helical wire segments can be insulated such that the wires do not touch each other at points where they cross over each other. Breaks in the wires can be staggered along the longitudinal axis of the device and/or circumferentially around the device to minimize formation of weak areas where wire breaks are aligned or grouped.
1. An elongated, MRI-compatible, interventional device comprising a plurality of helical wires arranged in an elongated tubular or rod-shaped configuration, the plurality of wires covered by electrically insulating material, wherein each of the plurality of helical wires comprises non-electrically-conductive breaks at intervals along the length of the wire such that the wire is segmented into a plurality of wire segments between the breaks, each wire segment having a length less than a threshold length, and wherein each wire segment is electrically insulated from the other wire segments of the interventional device;
wherein the threshold length is selected based on a field strength of a corresponding MRI field application such that the interventional device is safe for use in the corresponding MRI field application;
wherein the threshold length is less than an associated resonant length for the MRI field application.
2. The interventional device of claim 1 , wherein the threshold length is equal to or less than ¼ of a wavelength of a Larmor frequency in vivo of the corresponding MRI field.
3. The interventional device of claim 1 , wherein the corresponding MRI field application comprises a 3.0 Tesla MRI field and the threshold length is 5 cm or less, or the corresponding MRI field application comprises a 1.5 Tesla MRI field and the threshold length is 10 cm or less, or the corresponding MRI field application comprises a 0.5 Tesla MRI field and the threshold length is 30 cm or less.
4. The interventional device of claim 1 , wherein the wire segments of the interventional device do not substantially heat up when used in the corresponding MRI field application.
5. The interventional device of claim 1 , wherein each of the plurality of helical wires is individually covered in insulating material.
6. The interventional device of claim 1 , wherein the plurality of helical wires is encased in a tubular insulating material.
7. The interventional device of claim 1 , wherein the breaks in the plurality of helical wires are staggered along an axial dimension of the interventional device.
8. The interventional device of claim 1 , wherein no more than two breaks in the plurality of helical wires are located at the same axial position along the interventional device.
9. The interventional device of claim 1 , wherein each break in the plurality of helical wires is located at a different axial position along the interventional device.
10. The interventional device of claim 1 , wherein the breaks in the plurality of helical wires are staggered along a circumferential dimension of the interventional device.
11. The interventional device of claim 1 , wherein, in a longitudinal section of the interventional device in which each of the plurality of helical wires includes only one break, each of the breaks is located at a different circumferential position around the interventional device.
12. The interventional device of claim 1 , wherein the breaks in the plurality of helical wires are arranged in groups of two adjacent breaks.
13. The interventional device of claim 12 , wherein in each group, the two breaks are in two wires having the same helical chirality.
14. The interventional device of claim 1 , wherein each of the breaks is separated from the other breaks by at least one of the wire segments.
15. The interventional device of claim 1 , further comprising at least one MRI conspicuity marker.
16. The interventional device of claim 1 , wherein the plurality of helical wires are arranged in a braided pattern, with a portion of the plurality of wires having a first helical chirality and a portion of the plurality of wires having a second, opposite helical chirality.
17. The interventional device of claim 1 , wherein the plurality of helical wires are arranged in a diamond braid pattern.
18. The interventional device of claim 1 , wherein the plurality of helical wires comprises at least four wires, with half of the at least four wires having one helical chirality and half of the wires having an opposite helical chirality.
19. The interventional device of claim 16 , wherein each wire segment is electrically insulated from each other wire segment that it crosses radially over or crosses radially under.
20. The interventional device of claim 1 , wherein the plurality of helical wires have the same helical chirality.
21. The interventional device of claim 1 , wherein the plurality of helical wires are parallel to each other.
22. The interventional device of claim 1 , wherein the plurality of helical wires do not overlap each other.
23. The interventional device of claim 1 , wherein the plurality of helical wires are intercalated with each other.
24. The interventional device of claim 1 , wherein the plurality of helical wires comprises only two or three helical wires.
25. The interventional device of claim 1 , wherein the interventional device comprises a catheter.
26. The interventional device of claim 1 , wherein the interventional device comprises a guidewire.
27. A method comprising:
providing the interventional device of claim 1 , and
using the interventional device of claim 1 in an MRI field application without causing substantial heating or resonance of the interventional device caused by the MRI field.