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Publication numberUS20070032862 A1
Publication typeApplication
Application numberUS 11/388,090
Publication dateFeb 8, 2007
Filing dateMar 22, 2006
Priority dateAug 8, 2005
Also published asCA2617899A1, EP1915112A1, US7778684, US20070032861, WO2007018611A1
Publication number11388090, 388090, US 2007/0032862 A1, US 2007/032862 A1, US 20070032862 A1, US 20070032862A1, US 2007032862 A1, US 2007032862A1, US-A1-20070032862, US-A1-2007032862, US2007/0032862A1, US2007/032862A1, US20070032862 A1, US20070032862A1, US2007032862 A1, US2007032862A1
InventorsJan Weber, David Sogard, David Friesen, John Blix
Original AssigneeJan Weber, Sogard David J, Friesen David L, John Blix
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Medical devices
US 20070032862 A1
Abstract
In some embodiments, a method can include delivering an electrically conductive coil into a lumen of a subject. In certain embodiments, the method can further include delivering at least a portion of an endoprosthesis into a lumen of the electrically conductive coil. In some embodiments, the method may enhance the MRI visibility of material within a lumen of the endoprosthesis.
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Claims(28)
1. A method, comprising:
delivering an electrically conductive coil into a lumen of a subject; and
delivering at least a portion of an endoprosthesis into a lumen of the electrically conductive coil.
2. The method of claim 1, wherein the method comprises using a generally tubular member to deliver the electrically conductive coil into the lumen of the subject.
3. The method of claim 2, wherein delivering the electrically conductive coil into a lumen of a subject comprises separating an attached end of the electrically conductive coil from the generally tubular member.
4. The method of claim 3, wherein separating an attached end of the electrically conductive coil from the generally tubular member comprises electrolytically detaching the attached end of the electrically conductive coil from the generally tubular member.
5. The method of claim 3, wherein separating an attached end of the electrically conductive coil from the generally tubular member comprises mechanically detaching the attached end of the electrically conductive coil from the generally tubular member.
6. The method of claim 2, wherein the electrically conductive coil is attached to the generally tubular member by a bioerodible material.
7. The method of claim 2, wherein during delivery of the electrically conductive coil into the lumen of the subject, the electrically conductive coil is supported by the generally tubular member.
8. The method of claim 7, further comprising separating the electrically conductive coil from the generally tubular member so that the electrically conductive coil no longer is supported by the generally tubular member.
9. The method of claim 8, wherein separating the electrically conductive coil from the generally tubular member comprises rotating the generally tubular member.
10. The method of claim 8, wherein separating the electrically conductive coil from the generally tubular member comprises expanding the electrically conductive coil into the lumen of the subject.
11. The method of claim 1, further comprising viewing the endoprosthesis using magnetic resonance imaging.
12. The method of claim 1, wherein the electrically conductive coil forms a resonance circuit.
13. The method of claim 1, wherein the electrically conductive coil comprises a conductor connecting a first section of the electrically conductive coil to a second section of the electrically conductive coil.
14. The method of claim 1, further comprising connecting a proximal end of the electrically conductive coil to a distal end of the electrically conductive coil using a conductor.
15. The method of claim 1, wherein the electrically conductive coil comprises a superelastic material.
16. The method of claim 1, wherein delivering an electrically conductive coil into a lumen of a subject comprises delivering a sheath containing the electrically conductive coil into the lumen of the subject.
17. The method of claim 16, comprising rotating the sheath to deliver the electrically conductive coil from the sheath into the lumen of the subject.
18. The method of claim 16, wherein the sheath has an exterior surface and an interior surface that contacts the electrically conductive coil.
19. The method of claim 18, wherein the interior surface of the sheath defines at least one groove.
20. The method of claim 19, wherein the interior surface of the sheath defines a helical groove.
21. The method of claim 20, wherein the electrically conductive coil is disposed within the helical groove.
22. The method of claim 1, wherein the electrically conductive coil comprises a proximal end and a distal end, and the method comprises establishing electrical communication between the proximal end and the distal end.
23. The method of claim 22, wherein the method comprises establishing electrical communication between the proximal end and the distal end without using a solid conductor.
24. The method of claim 1, further comprising using magnetic resonance imaging to view an environment surrounding the electrically conductive coil prior to delivering at least a portion of an endoprosthesis into a lumen of the electrically conductive coil.
25. The method of claim 1, wherein the electrically conductive coil comprises a first capacitor, and the method further comprises flowing an electrical current through a circuit including the first capacitor.
26. The method of claim 25, wherein the electrical circuit further comprises a second capacitor.
27. The method of claim 1, wherein during delivery of the electrically conductive coil into the lumen of the subject, the electrically conductive coil is in contact with at least one electrical circuit component that is not a component of the electrically conductive coil.
28. The method of claim 1, wherein during delivery of the electrically conductive coil into the lumen of the subject, the electrically conductive coil resonates at the Larmor frequency of a proton in a one Tesla magnetic field, a 1.5 Tesla magnetic field, or a three Tesla magnetic field.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of, and claims priority under 35 U.S.C. § 120 to, U.S. patent application Ser. No. 11/198,961, filed on Aug. 8, 2005, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The invention relates to medical devices, and to related components and methods.

BACKGROUND

The body includes various passageways such as arteries, other blood vessels, and other body lumens. These passageways sometimes become occluded or weakened. For example, the passageways can be occluded by a tumor, restricted by plaque, or weakened by an aneurysm. When this occurs, the passageways can be reopened or reinforced, or even replaced, with a medical endoprosthesis. An endoprosthesis is typically a tubular member that is placed in a lumen in the body. Examples of endoprostheses include stents, stent-grafts, and covered stents.

An endoprosthesis can be delivered inside the body by a catheter that supports the endoprosthesis in a compacted or reduced-size form as the endoprosthesis is transported to a desired site. Upon reaching the site, the endoprosthesis is expanded, for example, so that it can contact the walls of the lumen.

When the endoprosthesis is advanced through the body, its progress can be monitored (e.g., tracked), so that the endoprosthesis can be delivered properly to a target site. After the endoprosthesis has been delivered to the target site, the endoprosthesis can be monitored to determine whether it has been placed properly and/or is functioning properly.

Methods of tracking and monitoring a medical device include X-ray fluoroscopy and magnetic resonance imaging (MRI). MRI is a non-invasive technique that uses a magnetic field and pulsed radio waves to image the body. In some MRI procedures, the patient is exposed to a static magnetic field, which interacts with certain atoms (e.g., hydrogen atoms) within the magnetic field (e.g., in the patient's body), causing the spins of the atoms' nuclei to become aligned relative to the magnetic field. Incident radio waves are then directed at the patient. The incident radio waves interact with atoms in the patient's body having a similar resonance frequency as the incident radio waves, thereby causing the atoms' nuclei to assume a temporary non-aligned high-energy state. After the incident radio pulse stops, the decay of the spins in these atomic nuclei to lower energy levels produces characteristic return radio waves. The return radio waves are detected by a scanner and processed by a computer to generate an image of the body.

SUMMARY

In one aspect, the invention features a method that includes delivering an electrically conductive coil into a lumen of a subject, and delivering at least a portion of an endoprosthesis into a lumen of the electrically conductive coil.

Embodiments can include one or more of the following features.

The method can include using a generally tubular member to deliver the electrically conductive coil into the lumen of the subject. In some embodiments, the electrically conductive coil can be attached to the generally tubular member. For example, in certain embodiments, a proximal end and/or a distal end of the electrically conductive coil can be attached to the generally tubular member. Delivering the electrically conductive coil into a lumen of a subject may include separating (e.g., electrolytically detaching, mechanically detaching) an attached end (e.g., a proximal end, a distal end) of the electrically conductive coil from the generally tubular member. In some embodiments, the electrically conductive coil can be attached to the generally tubular member by a bioerodible material. The method may include detaching the electrically conductive coil from the generally tubular member by eroding the bioerodible material.

During delivery of the electrically conductive coil into the lumen of the subject, the electrically conductive coil can be supported by the generally tubular member. In some embodiments, the method can include separating the electrically conductive coil from the generally tubular member so that the electrically conductive coil no longer is supported by the generally tubular member. The electrically conductive coil may be separated from the generally tubular member by rotating the generally tubular member, and/or by expanding the electrically conductive coil into the lumen of the subject.

Delivering an electrically conductive coil into a lumen of a subject can include delivering a sheath containing the electrically conductive coil into the lumen of the subject. In some embodiments, the method can include rotating the sheath to deliver the electrically conductive coil from the sheath into the lumen of the subject. In certain embodiments, the method can include proximally withdrawing the sheath. The interior surface of the sheath can contact the electrically conductive coil. In some embodiments, the interior surface of the sheath can have at least one groove, such as a helical groove. In certain embodiments (e.g., in certain embodiments in which the groove is a helical groove), the electrically conductive coil can be disposed within the groove. In some embodiments, the interior surface of the sheath may not have any grooves.

The method can include establishing electrical communication between a proximal end and a distal end of the electrically conductive coil. The electrical communication can be established using a solid conductor, such as a wire, or without using a solid conductor.

The method can include using magnetic resonance imaging to view an environment surrounding the electrically conductive coil prior to delivering at least a portion of an endoprosthesis into a lumen of the electrically conductive coil.

The electrically conductive coil can include a first capacitor, and the method can include flowing an electrical current through a circuit including the first capacitor. The electrical circuit can include at least two capacitors. During delivery of the electrically conductive coil into the lumen, the electrically conductive coil can be in contact with at least one electrical circuit component that is not a component of the electrically conductive coil. During delivery of the electrically conductive coil into the lumen, the electrically conductive coil can resonate at the Larmor frequency of a proton in a one Tesla magnetic field, a 1.5 Tesla magnetic field, or a three Tesla magnetic field.

The method can include expanding the endoprosthesis and/or viewing the endoprosthesis using magnetic resonance imaging.

The electrically conductive coil can form a resonance circuit. The resonance circuit can include at least one capacitor. In some embodiments, the capacitor can be supported by, and/or included in, the endoprosthesis. In certain embodiments, the capacitor may not be supported by the endoprosthesis, and/or may not be included in the endoprosthesis. The electrically conductive coil can include a conductor (e.g., a wire) connecting one section of the electrically conductive coil to another section of the electrically conductive coil. In some embodiments, the electrically conductive coil can include a conductor (e.g., a wire) connecting a proximal end of the electrically conductive coil to a distal end of the electrically conductive coil. In certain embodiments, the method can include connecting a proximal end of the electrically conductive coil to a distal end of the electrically conductive coil using a conductor (e.g., a wire).

The electrically conductive coil can include a superelastic material and/or a shape memory material. In some embodiments, the electrically conductive coil can include Nitinol.

The electrically conductive coil can be a self-expanding coil and/or a balloon-expandable coil.

The endoprosthesis can be a stent (e.g., a self-expanding stent, a balloon-expandable stent), a graft, a stent-graft, or a covered stent.

Embodiments may include one or more of the following advantages.

An electrically conductive coil can be relatively efficiently delivered to a target site, such as a lumen of a subject. In some embodiments, an electrically conductive coil can be delivered to a target site using a delivery device (e.g., a generally tubular member) to which the electrically conductive coil is attached. In certain embodiments, the electrically conductive coil can be attached to the delivery device by a bioerodible material. One or more body fluids (e.g., blood) at the target site can erode the bioerodible material and help to detach the coil from the delivery device.

In certain embodiments, an electrically conductive coil can be withdrawn back into a delivery device after being partially delivered from the delivery device. For example, in some embodiments in which an electrically conductive coil is partially delivered from a delivery device by rotating and withdrawing a sheath of the delivery device, the sheath can be rotated in the opposite direction to recapture the coil. It may be desirable to recapture a coil if, for example, the coil has mistakenly been delivered to a non-target site in the body of a subject.

In some embodiments, an electrically conductive coil can be adapted for use with multiple different types of endoprostheses. For example, an electrically conductive coil may be adapted for use with an endoprosthesis having one configuration, and with an endoprosthesis having a different configuration.

In certain embodiments, MRI, a non-invasive procedure, can be used to view material within the lumen of an endoprosthesis that is at least partially disposed within an electrically conductive coil. Thus, an operator (e.g., a physician) can assess the condition of a target site (e.g., for signs of restenosis) after implantation of the endoprosthesis (e.g., two weeks after implantation, one month after implantation). In some embodiments (e.g., in some embodiments in which an electrically conductive coil forms a resonance circuit), an electrically conductive coil can enhance the MRI visibility of material within the lumen of the endoprosthesis. In certain embodiments in which an electrically conductive coil forms a resonance circuit, the electrically conductive coil may increase the temperature of its immediate environment, but may not significantly increase the temperature of the rest of the body of the subject.

In some embodiments, an electrically conductive coil can be used both as an imaging coil (e.g., to provide an image of a lumen during delivery of the coil to a target site) and as a resonance circuit (e.g., once the coil has been delivered to a target site). Thus, the same electrically conductive coil can be used for multiple different purposes during one procedure.

Other aspects, features, and advantages are in the description, drawings, and claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is an illustration of an embodiment of an endoprosthesis disposed within an embodiment of an electrically conductive coil in a lumen of a subject.

FIG. 2 is a perspective view of the endoprosthesis of FIG. 1.

FIG. 3 is a side view of the electrically conductive coil of FIG. 1.

FIG. 4 is a schematic illustration of an embodiment of a resonance circuit.

FIG. 5A is an illustration of a embodiment of a coil delivery system within a lumen of a subject.

FIGS. 5B and 5C are illustrations of the coil delivery system of FIG. 5A, during delivery of an embodiment of an electrically conductive coil into the lumen of the subject.

FIG. 5D is an illustration of the electrically conductive coil of FIGS. 5B and 5C, once the electrically conductive coil has been delivered into the lumen of the subject.

FIG. 5E is an illustration of an embodiment of an endoprosthesis disposed within the electrically conductive coil of FIGS. 5B-5D.

FIG. 6A is an illustration of an embodiment of a coil delivery system within a lumen of a subject.

FIG. 6B is an enlarged view of region 6B of FIG. 6A.

FIG. 6C is an illustration of the coil delivery system of FIG. 6A, during delivery of an embodiment of an electrically conductive coil into the lumen of the subject.

FIG. 6D is an illustration of the electrically conductive coil of FIG. 6C, once the electrically conductive coil has been delivered into the lumen of the subject.

FIG. 6E is an illustration of an embodiment of an endoprosthesis disposed within the electrically conductive coil of FIGS. 6C and 6D.

FIG. 7 is a side perspective view of the electrically conductive coil of FIGS. 6C-6E.

FIG. 8A is an illustration of an embodiment of a coil delivery system within a lumen of a subject.

FIG. 8B is an illustration of the coil delivery system of FIG. 8A, during delivery of an embodiment of an electrically conductive coil into the lumen of the subject.

FIG. 8C is an illustration of the electrically conductive coil of FIG. 8B, once the electrically conductive coil has been delivered into the lumen of the subject.

FIG. 8D is an illustration of an embodiment of an endoprosthesis disposed within the electrically conductive coil of FIGS. 8B and 8C.

FIG. 9 is a side perspective view of the electrically conductive coil of FIGS. 8B-8D.

FIG. 10 is a side view of an embodiment of a coil delivery system.

FIG. 11A is a perspective view of an embodiment of a coil delivery system.

FIG. 11B is a cross-sectional view of the coil delivery system of FIG. 11A, taken along line 11B-11B.

FIG. 12 is a side perspective view of an embodiment of a coil delivery system and an embodiment of an electrically conductive coil.

FIG. 13A is an illustration of a embodiment of a coil delivery system within a lumen of a subject.

FIGS. 13B and 13C are illustrations of the coil delivery system of FIG. 13A, during delivery of an embodiment of an electrically conductive coil into the lumen of the subject.

FIGS. 14A and 14B illustrate the delivery of an embodiment of an electrically conductive coil into the lumen of a subject.

FIG. 15A is an illustration of an embodiment of a coil delivery system and an embodiment of an electrically conductive coil within a lumen of a subject.

FIG. 15B is an illustration of the coil delivery system and electrically conductive coil of FIG. 15A, during delivery of the electrically conductive coil into the lumen of the subject.

FIG. 15C is an illustration of the electrically conductive coil of FIG. 15A, once the electrically conductive coil has been delivered into the lumen of the subject.

FIG. 15D is an enlarged view of a portion of the coil delivery system and the electrically conductive coil of FIG. 15A.

FIG. 16A is an illustration of an embodiment of a coil delivery system and an embodiment of an electrically conductive coil, disposed within a lumen of a subject.

FIG. 16B is an illustration of the coil delivery system and the electrically conductive coil of FIG. 16A, during delivery of the electrically conductive coil into the lumen of the subject.

FIG. 17 is an illustration of an embodiment of a coil delivery system and an embodiment of an electrically conductive coil, disposed within a lumen of a subject.

FIG. 18 is an illustration of an embodiment of a coil delivery system and an embodiment of an electrically conductive coil, disposed within a lumen of a subject.

FIG. 19A is an illustration of an embodiment of a coil delivery system and an embodiment of an electrically conductive coil, disposed within a lumen of a subject.

FIG. 19B is an illustration of the coil delivery system and the electrically conductive coil of FIG. 19A, during delivery of the electrically conductive coil into the lumen of the subject.

FIG. 19C is an illustration of the electrically conductive coil of FIGS. 19A and 19B, once the electrically conductive coil has been delivered into the lumen of the subject.

FIG. 20 is a side view of an embodiment of an electrically conductive coil.

FIG. 21 is a side view of an embodiment of an electrically conductive coil.

FIG. 22 is a side view of an embodiment of an electrically conductive coil.

FIG. 23A is an illustration of an embodiment of a coil delivery system and an embodiment of an electrically conductive coil, disposed within a lumen of a subject.

FIG. 23B is an illustration of the coil delivery system and the electrically conductive coil of FIG. 23A, after the electrically conductive coil has been delivered into the lumen of the subject.

FIG. 24 is a cross-sectional view of an embodiment of a coil delivery system and an embodiment of an electrically conductive coil.

DETAILED DESCRIPTION

Referring to FIG. 1, an electrically conductive coil 10 is disposed within a lumen 12 of a subject. Coil 10 has a proximal end 14 and a distal end 16, which are connected to each other by a wire 18. A stent 20, which includes a lumen 22 (FIG. 2) is disposed within a lumen 24 (FIG. 3) of coil 10.

The structure of a stent such as stent 20 may adversely affect the MRI-visibility of material within the lumen of the stent. Without wishing to be bound by theory, it is believed that in some embodiments, when a stent is exposed to a variable magnetic field during MRI, the stent can induce a current that limits the visibility of material within the lumen of the stent. Specifically, during MRI, an incident electromagnetic field is applied to a stent. The magnetic environment of the stent can be constant or variable, such as when the stent moves within the magnetic field (e.g., from a beating heart) or when the incident magnetic field is varied. When there is a change in the magnetic environment of the stent, which can act as a coil or a solenoid, an induced electromotive force (emf) is generated, according to Faraday's Law. The induced emf in turn can produce an eddy current that induces a magnetic field that opposes the change in magnetic field. The induced magnetic field can oppose the incident magnetic field, thereby reducing (e.g., distorting) the visibility of material in the lumen of the stent. A similar effect can be caused by a radiofrequency pulse applied during MRI. Thus, the ability to use MRI to view and assess the condition of a target site that includes a stent such as stent 20 can be limited.

Coil 10 can help to increase the MRI visibility of material within lumen 22 of stent 20. Coil 10 forms a resonance circuit that is tuned to the RF frequency of the MRI system that is used to view stent 10. FIG. 4 shows a schematic illustration of a resonance circuit 50, which includes an inductor 54, a resistor 56, and a capacitor 58. In some embodiments, coil 10 can form an inductor, and/or a capacitor (e.g., capacitor 58) can be applied (e.g., stamped) onto coil 10, and/or can be embedded into coil 10. In certain embodiments, capacitor 58 of resonance circuit 50 may be a part of stent 20 (e.g., may be carried by stent 20), or may not be a part of stent 20 (e.g., may not be carried by stent 20). Without wishing to be bound by theory, it is believed that the presence of a resonance circuit such as coil 10 in the vicinity of stent 20 can help to at least partially reduce the effect of the above-described induced magnetic field. When stent 20 is viewed using MRI, coil 10 can locally enhance (e.g., amplify) the RF field that is generated by the MRI system. Thus, coil 10 can be used to increase the RF energy level locally (near stent 20), without also significantly increasing the RF energy level in the rest of the body of the subject. This can, for example, limit the likelihood of a significant increase in the temperature of the rest of the body of the subject. The increase in RF energy level near stent 20 can increase the visibility of material within lumen 22 of stent 20. Resonance circuits are further described, for example, in Melzer et al., U.S. Pat. No. 6,280,385.

A coil such as coil 10 can be delivered into lumen 12 using any of a number of different methods.

For example, FIGS. 5A through 5E illustrate the delivery of coil 10 into lumen 12 using a delivery device 100. Delivery device 100 can be, for example, a catheter system, such as one of the catheter systems described below. As shown in FIG. 5A, delivery device 100 includes a generally tubular inner member 102, a tip 104 at the distal end 106 of inner member 102, and a sheath 108 surrounding inner member 102. Coil 10, which is formed of a superelastic material, is loaded onto inner member 102, and is restrained on inner member 102 by two bioerodible strips 110 and 112.

Referring to FIG. 5B, to deliver coil 10 into lumen 12, sheath 108 is retracted proximally (in the direction of arrow A), exposing inner member 102. Over time, bioerodible strips 110 and 112 erode (e.g., as a result of being exposed to blood and/or other body fluids in lumen 12). As shown in FIG. 5C, bioerodible strips 110 and 112 eventually erode sufficiently to allow coil 10 to expand away from inner member 102 and into lumen 12.

Referring now to FIG. 5D, during and/or after expansion of coil 10, delivery device 100 is retracted from lumen 12, leaving coil 10 in lumen 12. Referring to FIG. 5E, stent 20 is then delivered into lumen 24 (FIG. 5D) of coil 10. Stent 20 can be delivered into lumen 24 and expanded within lumen 24 using, for example, a stent delivery system such as a catheter system. Examples of catheter systems include self-expandable stent delivery systems, and balloon catheter systems, such as single-operator exchange catheter systems, over-the-wire catheter systems, and fixed-wire catheter systems. Single-operator exchange catheters are described, for example, in Keith, U.S. Pat. No. 5,156,594, and in Stivland et al., U.S. Pat. No. 6,712,807. Over-the-wire catheters are described, for example, in Schoenle et al., U.S. Patent Application Publication No. US 2004/0131808 A1, published on Jul. 8, 2004. Fixed-wire catheters are described, for example, in Segar, U.S. Pat. No. 5,593,419. Catheter systems are also described in, for example, Wang, U.S. Pat. No. 5,195,969, and Hamlin, U.S. Pat. No. 5,270,086. Examples of commercially available balloon catheters include the Monorail™ family of balloon catheters (Boston Scientific Scimed, Inc., Maple Grove, Minn.). Stents and stent delivery are also exemplified by the Radius® or Symbiot® systems (Boston Scientific Scimed, Inc., Maple Grove, Minn.).

Bioerodible strips 110 and 112 each can include one or more bioerodible materials. In some embodiments, bioerodible strips 110 and 112 can include one or more of the same bioerodible materials. Examples of bioerodible materials include non-metallic bioerodible materials, such as polysaccharides (e.g., alginate); alginate salts (e.g., sodium alginate); sugars (e.g., sucrose (C12H22O11), dextrose (C6H12O6), sorbose (C6H12O6)); sugar derivatives (e.g., glucosamine (C6H13NO5), sugar alcohols such as mannitol (C6H14O6)); inorganic, ionic salts (e.g., sodium chloride (NaCl), potassium chloride (KCl), sodium carbonate (Na2CO3)); water-soluble polymers (e.g., a polyvinyl alcohol, such as a polyvinyl alcohol that has not been cross-linked); biodegradable poly DL-lactide-poly ethylene glycol (PELA); hydrogels (e.g., polyacrylic acid, hyaluronic acid, gelatin, carboxymethyl cellulose); polyethylene glycol (PEG); chitosan; polyesters (e.g., a polycaprolactone); and poly(lactic-co-glycolic) acids (e.g., a poly(d-lactic-co-glycolic) acid).

Other examples of bioerodible materials include bioerodible polyelectrolytes, such as heparin, polyglycolic acid (PGA), polylactic acid (PLA), polyamides, poly-2-hydroxy-butyrate (PHB), polycaprolactone (PCL), poly(lactic-co-glycolic)acid (PLGA), protamine sulfate, polyallylamine, polydiallyldimethylammonium species (e.g., poly(diallyl-dimethylammonium chloride) (PDADMA, Aldrich)), polyethyleneimine, chitosan, eudragit, gelatin, spermidine, albumin, polyacrylic acid, sodium alginate, poly(styrene sulfonate) (PSS, Scientific Polymer Products), hyaluronic acid, carrageenan, chondroitin sulfate, carboxymethylcellulose, polypeptides, proteins, DNA, and poly(N-octyl-4-vinyl pyridinium iodide) (PNOVP). Polyelectrolytes are described, for example, in Tarek R. Farhat and Joseph B. Schlenoff, “Corrosion Control Using Polyelectrolyte Multilayers”, Electrochemical and Solid State Letters, 5 (4) B13-B15 (2002), and in Weber, U.S. patent application Ser. No. 11/127,968, filed on May 12, 2005, and entitled “Medical Devices and Methods of Making the Same”. Bioerodible materials are described, for example, in Colen et al., U.S. Patent Application Publication No. US 2005/0192657 A1, published on Sep. 1, 2005, and entitled “Medical Devices”.

As another example, FIGS. 6A-6E illustrate a method of delivering a coil 200 into a lumen 204 of a subject using a delivery system 202. As shown in FIG. 6A, delivery system 202 is formed of a generally tubular member 206 with a tip 208. Coil 200, which is formed of a shape memory material, is supported by generally tubular member 206. The proximal end 210 of coil 200 is attached to generally tubular member 206 by a bioerodible connector 212, and the distal end 214 of coil 200 is attached to generally tubular member 206 by a bioerodible connector 216 (shown in an enlarged view in FIG. 6B). Bioerodible connector 212 is formed of a different material from bioerodible connector 216. As shown in FIG. 6C, bioerodible connector 216 erodes before bioerodible connector 212, so that coil 200 first starts to expand away from generally tubular member 206 at its distal end 214. To aid in the expansion and placement of coil 200 in lumen 204, delivery system 202 is rotated in the direction of arrow A1 and is withdrawn proximally (in the direction of arrow A2). The rotation of delivery system 202 in the direction of arrow A1 can help to force coil 200 against the wall 205 of lumen 204, thereby positioning coil 200 within lumen 204. In some embodiments, coil 200 can include a hook (not shown) at its distal end 201 (FIG. 6C) that can hook into wall 205, further helping to position coil 200 within lumen 204. Eventually, bioerodible connector 212 erodes sufficiently to allow coil 200 to expand away from generally tubular member 206 at its proximal end 210 (FIGS. 6A and 6D), as well. Delivery system 202 is then removed from lumen 204, leaving expanded coil 200, which has a lumen 218, within lumen 204 (FIG. 6D). Referring now to FIG. 6E, a stent 220 is then delivered into lumen 218 of coil 200.

Bioerodible connectors 212 and/or 216 may be formed, for example, of one or more of the bioerodible materials described above. In certain embodiments, bioerodible connectors 212 and/or 216 can be attached to coil 200 and/or generally tubular member 206 using an adhesive. Examples of adhesives include acrylics, cyanoacrylate, epoxies, and polyurethane. In some embodiments, bioerodible connectors 212 and/or 216 can be attached to coil 200 and/or generally tubular member 206 using ultrasonic welding, laser welding, ultraviolet bonding, and/or heat bonding. In certain embodiments, bioerodible connectors 212 and/or 216 can be attached to coil 200 and/or generally tubular member 206 by suspending the bioerodible material of bioerodible connectors 212 and/or 216 in a substrate (e.g., styrene-isobutylene-styrene) that is attached to and/or coated on the coil and/or generally tubular member. While bioerodible connectors that are made of different materials have been described, in some embodiments, bioerodible connectors can be made of the same material.

As shown in FIGS. 6A-6E, coil 200 does not include a solid conductor (e.g., a wire) connecting its proximal and distal ends. However, coil 200 can still form a resonance circuit. FIG. 7 shows an enlarged view of coil 200. Referring to FIG. 7, coil 200 includes an insulated region 230 (e.g., so that coil 200 has limited or no electrical contact with a stent that is disposed within its lumen), a conductive region 232 at its proximal end 210, and a conductive region 234 at its distal end 214. When coil 200 is disposed at a target site (e.g., within a lumen of a subject, such as lumen 204), conductive regions 232 and 234 can be in electrical communication with each other (e.g., through blood and/or other body fluids, and/or through the structure of stent 220), so that coil 200 is able to carry a current.

FIGS. 8A-8D illustrate another method of delivering a coil into a lumen of a subject. As shown in FIG. 8A, a delivery system 304 includes a generally tubular inner member 306, a tip 308 at the distal end 310 of inner member 306, and a sheath 312 surrounding inner member 306. Sheath 312 has an interior surface 314 and an exterior surface 316. On its interior surface 314, sheath 312 has helical grooves 318. Coil 300 is disposed within grooves 318.

As shown in FIG. 8B, to deliver coil 300 into a lumen 302 of a subject, sheath 312 is rotated in the direction of arrow A3 while being withdrawn proximally (in the direction of arrow A4). As sheath 312 is rotated and withdrawn, coil 300 exits sheath 312 and expands into lumen 302. In some embodiments, proximal end 324 of coil 300 can be attached to inner member 306. For example, in certain embodiments, inner member 306 can have a hole in it, and proximal end 324 of coil 300 can be placed in the hole. In some embodiments, proximal end 324 of coil 300 can be attached to inner member 306 with a bioerodible connector. In certain embodiments, the attachment of proximal end 324 of coil 300 to inner member 306 can limit the likelihood that coil 300 will be withdrawn with sheath 312. In some embodiments, coil 300 can become detached from inner member 306 once sheath 312 has been withdrawn from the region in which coil 300 is located. Eventually, the entirety of coil 300 is delivered into lumen 302, and delivery system 304 is removed from lumen 302, leaving expanded coil 300, which has a lumen 320, within lumen 302 (FIG. 8C). Referring now to FIG. 8D, after coil 300 has been delivered into lumen 302, a stent 322 is delivered into lumen 320 of coil 300.

In some embodiments (e.g., if it is determined after partial delivery of coil 300 that coil 300 is being delivered to an untargeted location), coil 300 can be withdrawn back into sheath 312 by rotating sheath 312 in a direction opposite to that of arrow A3.

Like coil 200, coil 300 does not include a wire connecting its proximal end 324 and its distal end 326. However, as shown in FIG. 9, coil 300 has an insulated region 328, a conductive region 330 at its proximal end 324, and a conductive region 332 at its distal end 326. Thus, like coil 200, coil 300 can conduct current (e.g., through blood and/or other body fluids, and/or through the structure of stent 322).

An electrically conductive coil, such as one of the electrically conductive coils described above, can be formed of a relatively elastic material, such as a superelastic or pseudo-elastic material (e.g., a superelastic or pseudo-elastic metal alloy). Such materials can allow the coil to temporarily deform and then regain its shape, without experiencing a permanent deformation. Examples of superelastic materials include a Nitinol (e.g., 55% nickel, 45% titanium), silver-cadmium (Ag—Cd), gold-cadmium (Au—Cd), gold-copper-zinc (Au—Cu—Zn), copper-aluminum-nickel (Cu—Al—Ni), copper-gold-zinc (Cu—Au—Zn), copper-zinc (Cu—Zn), copper-zinc-aluminum (Cu—Zn—Al), copper-zinc-tin (Cu—Zn—Sn), copper-zinc-xenon (Cu—Zn—Xe), indium-thallium (In—Ti), nickel-titanium-vanadium (Ni—Ti—V), titanium-molybdenum (Ti—Mo), titanium-niobium-tantalum-zirconium (Ti—Nb—Ta—Zr), and copper-tin (Cu—Sn). See, e.g., Schetsky, L. McDonald, “Shape Memory Alloys”, Encyclopedia of Chemical Technology (3rd ed.), John Wiley & Sons, 1982, vol. 20, pp. 726-736, for a full discussion of superelastic alloys. Other examples of materials include one or more precursors of superelastic alloys, i.e., those alloys that have the same chemical constituents as superelastic alloys, but have not been processed to impart the superelastic property under the conditions of use. Such alloys are further described, for example, in PCT Application No. US91/02420.

In certain embodiments, an electrically conductive coil can be formed of a shape memory material. Examples of shape memory materials include metal alloys, such as Nitinol (e.g., 55% nickel, 45% titanium), silver-cadmium (Ag—Cd), gold-cadmium (Au—Cd), gold-copper-zinc (Au—Cu—Zn), copper-aluminum-nickel (Cu—Al—Ni), copper-gold-zinc (Cu—Au—Zn), copper-zinc (Cu—Zn), copper-zinc-aluminum (Cu—Zn—Al), copper-zinc-tin (Cu—Zn—Sn), copper-zinc-xenon (Cu—Zn—Xe), iron beryllium (Fe3Be), iron platinum (Fe3Pt), indium-thallium (In—Tl), iron-manganese (Fe—Mn), nickel-titanium-vanadium (Ni—Ti—V), iron-nickel-titanium-cobalt (Fe—Ni—Ti—Co) and copper-tin (Cu—Sn). See, e.g., Schetsky, L. McDonald, “Shape Memory Alloys”, Encyclopedia of Chemical Technology (3rd ed.), John Wiley & Sons, 1982, vol. 20, pp. 726-736. In some embodiments, an electrically conductive coil can be formed of a shape-memory material with a coating over it (e.g., a biocompatible coating). The coating can act as an insulator or as a conductor. In certain embodiments, the coating can be formed of gold (e.g., sputtered gold). In some embodiments, an electrically conductive coil can be formed of a polymeric shape-memory material in combination with at least one conductive material. The conductive material can be, for example, in the form of a strip and/or a coating (e.g., formed by sputtering) on the polymeric shape-memory material. As an example, in certain embodiments, an electrically conductive coil can be formed of a shape-memory polyurethane and can have a gold coating.

While shape memory materials have been described, in some embodiments, an electrically conductive coil can be formed of one or more other materials, such as spring steel and/or stainless steel. In certain embodiments, an electrically conductive coil can be formed out of one or more electrically conductive polymers. Examples of electrically conductive polymers include polyaniline, polypyrrole, and polythiopene.

In some embodiments, an electrically conductive coil can be formed of a material that is more ductile than the material of a stent that is at least partially disposed within the electrically conductive coil. This can, for example, allow the coil to adapt to the expansion of the stent (e.g., by moving to accommodate the stent), and/or can limit the likelihood of the coil restricting the expansion of the stent.

In some embodiments, an electrically conductive coil can be partially or entirely covered (e.g., coated) with an insulating material (e.g., a biocompatible insulating material). The insulating material can, for example, help to electrically isolate the coil from a stent that is at least partially disposed within the coil. Examples of insulating materials include polymers, such as polymers having a relatively high volume resistivity (e.g., more than about 107 Ohm-cm). Examples of polymers that can be used as insulating materials include polyimides, polystyrenes, polyamide 12, polytetrafluoroethylene (Teflon®), expanded polytetrafluoroethylene (e-PTFE), polyvinylidene difluoride (PVDF), polyurethanes, and silicone rubber. Additional examples of insulating materials include aluminum nitride (e.g., having a volume resistivity of about 1011 Ohm-cm) and diamond-like coatings. Diamond-like coatings are described, for example, in Straumal et al., “Vacuum Arc Deposition of Protective Layers on Glass and Polymer Substrates”, Thin Solid Films 383 (2001) 224-226. Further examples of insulating materials include heat-shrink materials (e.g., polyethylene terephthalate (PET)). In some embodiments, a heat-shrink coating on a coil can be relatively thin (e.g., can have a thickness of less than about five nanometers). In certain embodiments, an insulating layer (e.g., a polymer insulating layer) can be applied to a coil using a dip-coating process and/or a spraying process. In some embodiments, the surface of an electrically conductive coil can be oxidized to provide an insulating layer on the coil.

Typically, an electrically conductive coil can have dimensions that allow the coil to fit within a target site and/or to accommodate a stent within the lumen of the coil.

In some embodiments, a coil can have an expanded diameter of at least about one millimeter (e.g., at least about 1.5 millimeter, at least about two millimeters, at least about five millimeters, at least about 10 millimeters, at least about 12 millimeters, at least about 15 millimeters, at least about 20 millimeters, at least about 24 millimeters, at least about 30 millimeters, at least about 35 millimeters, at least about 40 millimeters), and/or at most about 46 millimeters (e.g., at most about 40 millimeters, at most about 35 millimeters, at most about 30 millimeters, at most about 24 millimeters, at most about 20 millimeters, at most about 15 millimeters, at most about 12 millimeters, at most about 10 millimeters, at most about five millimeters, at most about two millimeters, at most about 1.5 millimeter). In certain embodiments (e.g., certain embodiments in which a coil is adapted for use in a coronary vessel), a coil can have an expanded diameter of about two millimeters. In some embodiments (e.g., some embodiments in which a coil is adapted for use in an iliac vessel), a coil can have an expanded diameter of about 12 millimeters. In certain embodiments (e.g., certain embodiments in which a coil is adapted for use in an abdominal aortic aneurysm (AAA) application), a coil can have an expanded diameter of about 24 millimeters. In some embodiments (e.g., some embodiments in which a coil is adapted for use in an aortic application), a coil can have an expanded diameter of about 40 millimeters. In certain embodiments, a coil can be expanded to a diameter that is at least four times as large as the diameter of the coil when the coil is not expanded. For example, a coil may have a non-expanded diameter of about two millimeters, and an expanded diameter of about six millimeters, or may have a non-expanded diameter of about 1.5 millimeters, and an expanded diameter of about 4.5 millimeters.

In certain embodiments, a coil can have a length of at least about 0.4 centimeter (e.g., at least about 0.5 centimeter, at least about one centimeter, at least about five centimeters, at least about 10 centimeters, at least about 15 centimeters, at least about 20 centimeters, at least about 25 centimeters), and/or at most about 30 centimeters (e.g., at most about 25 centimeters, at most about 20 centimeters, at most about 15 centimeters, at most about 10 centimeters, at most about five centimeters, at most about one centimeter, at most about 0.5 centimeter). For example, in some embodiments (e.g., some embodiments in which a coil is adapted for use with a neurovascular stent), a coil can have a length of about 0.5 centimeter. In certain embodiments (e.g., certain embodiments in which a coil is adapted for use with an abdominal aortic aneurysm (AAA) stent and/or a gastrointestinal stent), a coil can have a length of about 30 centimeters.

In some embodiments, a coil can be formed of a wire having a diameter of at least about seven microns (e.g., at least about 10 microns, at least about 15 microns, at least about 20 microns, at least about 25 microns, at least about 50 microns, at least about 100 microns, at least about 150 microns), and/or at most about 200 microns (e.g., at most about 150 microns, at most about 100 microns, at most about 50 microns, at most about 25 microns, at most about 20 microns, at most about 15 microns, at most about 10 microns). In certain embodiments, a coil can be formed of a wire having an extended length of at least about three millimeters (e.g., at least about five millimeters, at least about 10 millimeters, at least about 50 millimeters, at least about 100 millimeters, at least about 500 millimeters, at least about 1000 millimeters, at least about 2000 millimeters, at least about 3000 millimeters, at least about 4000 millimeters), and/or at most about 4800 millimeters (e.g., at most about 4000 millimeters, at most about 3000 millimeters, at most about 2000 millimeters, at most about 1000 millimeters, at most about 500 millimeters, at most about 100 millimeters, at most about 50 millimeters, at most about 10 millimeters, at most about five millimeters).

In some embodiments, a coil can have a pitch of at least about 14 microns (e.g., at least about 25 microns, at least about 50 microns, at least about 100 microns, at least about 150 microns, at least about 200 microns, at least about 300 microns, at least about 400 microns, at least about 500 microns, at least about 600 microns, at least about 700 microns, at least about 800 microns, at least about 900 microns), and/or at most about 1000 microns (e.g., at most about 900 microns, at most about 800 microns, at most about 700 microns, at most about 600 microns, at most about 500 microns, at most about 400 microns, at most about 300 microns, at most about 200 microns, at most about 150 microns, at most about 100 microns, at most about 50 microns, at most about 25 microns). The pitch of a coil is the sum of the thickness of one winding of a wire used to form the coil and the amount of space between that winding and a consecutive winding of the wire. When the windings of a coil are flush with each other, the pitch of the coil is equal to the thickness of one winding of the wire that is used to form the coil and to the diameter of the wire that is used to form the coil.

A stent that is used in conjunction with an electrically conductive coil, such as one of the stents described above, can be a self-expandable stent, a balloon-expandable stent, or a combination of both (e.g., Andersen et al., U.S. Pat. No. 5,366,504).

In some embodiments, a stent can be formed of an MRI-compatible material, such as a non-ferromagnetic material. As an example, a stent can be formed of one or more materials with a relatively low magnetic susceptibility. For example, a stent can be formed of a material (e.g., a metal, a metal alloy) with a magnetic susceptibility of less than 0.9×10−3 (e.g., less than 0.871×10−3, less than 0.3×10−3, less than −0.2×10−3). In certain embodiments, a stent can include a material with a magnetic susceptibility that is lower than the magnetic susceptibility of stainless steel and/or Nitinol. In some embodiments, a material with a relatively low magnetic susceptibility can be unlikely to move substantially as a result of being exposed to MRI. Materials having a relatively low magnetic susceptibility are described, for example, in Stinson et al., U.S. patent application Ser. No. 11/004,009, filed on Dec. 3, 2004, and entitled “Medical Devices and Methods of Making the Same”.

In certain embodiments in which a stent is a self-expandable stent, the stent can include a relatively elastic material, such as a superelastic or pseudo-elastic metal alloy. Such materials can cause the stent to be relatively flexible during delivery, thereby allowing the stent to be safely advanced through a lumen (e.g., through a relatively tortuous vessel). Alternatively or additionally, such materials can allow the stent to temporarily deform (e.g., upon experiencing a temporary extrinsic load), and then regain its shape (e.g., after the load has been removed), without experiencing a permanent deformation, which could lead to re-occlusion, embolization, and/or perforation of the lumen wall. Examples of such materials are provided above with reference to electrically conductive coil materials.

In certain embodiments, a stent can include one or more materials that can be used for a balloon-expandable stent, such as noble metals (e.g., platinum, gold, palladium), refractory metals (e.g., tantalum, tungsten, molybdenum, rhenium), and alloys thereof. Other examples of stent materials include titanium, titanium alloys (e.g., alloys containing noble and/or refractory metals), vanadium alloys, stainless steels, stainless steels alloyed with noble and/or refractory metals, nickel-based alloys (e.g., those that contain platinum, gold, and/or tantalum), iron-based alloys (e.g., those that contain platinum, gold, and/or tantalum), cobalt-based alloys (e.g., those that contain platinum, gold, and/or tantalum), aluminum alloys, zirconium alloys, and niobium alloys. Metal alloys are described, for example, in Stinson, U.S. Patent Application Publication No. US 2005/0070990 A1, published on Mar. 31, 2005.

In some embodiments, a stent can include one or more radiopaque materials (e.g., metals, metal alloys), which can cause the stent to be visible using X-ray fluoroscopy (e.g., allowing the stent to be tracked as it is delivered to a target site). Examples of radiopaque materials include metallic elements having atomic numbers greater than 26 (e.g., greater than 43), and/or those materials having a density greater than about eight grams per cubic centimeter (e.g., greater than about 9.9 grams per cubic centimeter, at least about 25 grams per cubic centimeter, at least about 50 grams per cubic centimeter).

In some embodiments, a medical device can include a material (e.g., a metal, a metal alloy) with a magnetic susceptibility of less than 0.9×10−3 and a density of greater than about eight grams per cubic centimeter. For example, a medical device can include platinum, tantalum, palladium, and/or molybdenum. In certain embodiments, a radiopaque material can be relatively absorptive of X-rays. For example, the radiopaque material can have a linear attenuation coefficient of at least 25 cm−1 (e.g., at least 50 cm−1) at 100 keV. Examples of radiopaque materials include tantalum, platinum, iridium, palladium, tungsten, gold, ruthenium, niobium, and rhenium. The radiopaque material can include an alloy, such as a binary, a ternary or more complex alloy, containing one or more elements listed above with one or more other elements such as iron, nickel, cobalt, or titanium. The radiopaque material can, for example, be more radiopaque than stainless steel. In some embodiments, the radiopaque material can be more radiopaque than iron and/or Nitinol.

A stent can be of any desired shape and size (e.g., a coronary stent, an aortic stent, a peripheral vascular stent, a gastrointestinal stent, a urology stent, a neurology stent). Depending on the application, a stent can have an expanded diameter of, for example, from about one millimeter to about 46 millimeters. In certain embodiments, a coronary stent can have an expanded diameter of from about 1.5 millimeters to about six millimeters (e.g., from about two millimeters to about six millimeters). In some embodiments, a peripheral stent can have an expanded diameter of from about four millimeters to about 24 millimeters. In certain embodiments, a gastrointestinal and/or urology stent can have an expanded diameter of from about six millimeters to about 30 millimeters. In some embodiments, a neurology stent can have an expanded diameter of from about one millimeter to about 12 millimeters. In certain embodiments, an abdominal aortic aneurysm (AAA) stent and/or a thoracic aortic aneurysm (TAA) stent can have an expanded diameter from about 20 millimeters to about 46 millimeters.

While certain embodiments have been described, other embodiments are possible.

As an example, in some embodiments, a bioerodible material that is used to attach a coil to a delivery device can be eroded by exposure to a stimulus and/or a material that is adapted to erode the bioerodible material. For example, in some embodiments, a bioerodible material can be contacted with an agent (e.g., an alcohol, hydrochloric acid, sodium hydroxide, sodium citrate, sodium hexa-metaphosphate) that can dissolve or erode at least a portion of the bioerodible material. The agent can be applied to the bioerodible material prior to and/or during delivery of the coil to a target site. For example, in some embodiments in which sodium alginate is used as a bioerodible material, at least a portion of the sodium alginate can be dissolved by contacting the sodium alginate with sodium hexa-metaphosphate. In certain embodiments, an agent that is adapted to dissolve or erode a bioerodible material that is used to attach a coil to a delivery device can be added into the delivery device (e.g., into a space in the delivery device in which the coil is located) prior to and/or during delivery of the coil to a target site. In some embodiments, a change in temperature, pH, and/or pressure may be used to detach a coil from a delivery device. In certain embodiments, an exposure to energy (e.g., optical energy, electrical energy) may be used to detach a coil from a delivery device. Attachment materials and methods of detachment are described, for example, in Bertolino et al., U.S. Patent Application Publication No. US 2004/0024441 A1, published on Feb. 5, 2004.

As another example, while delivery of a coil by erosion of bioerodible connectors has been described, in some embodiments, a coil can be detached from a delivery device using a different method. For example, in certain embodiments, electrolytic disintegration can be used to detach a coil from a delivery device. A point of attachment between the coil and the delivery device may be weaker than other regions of the coil. As current flows through the coil, the current can cause the point of attachment to electrolytically disintegrate, thereby causing the coil to become detached from the delivery device. Electrolytic disintegration is described, for example, in Guglielmi et al., U.S. Pat. No. 5,895,385, and in Guglielmi et al., U.S. Pat. No. 5,944,714.

As an additional example, in some embodiments, an electrically conductive coil and a wire attached to the electrically conductive coil can both be wound around a delivery device. For example, FIG. 10 shows a delivery device 350, and an electrically conductive coil 352 and a wire 354 both wound around delivery device 350. Electrically conductive coil 352 and wire 354 are connected to each other, and are attached to delivery device 350 by bioerodible connectors 356 and 358. In some embodiments, after delivery device 350 has been delivered to a target site (e.g., a lumen of a subject), and bioerodible connector 356 and/or 358 has eroded, delivery device 350 can be rotated and withdrawn to deliver electrically conductive coil 352 and wire 354 to the target site.

As shown in FIG. 10, in certain embodiments, a wire that is wound around a delivery device can have fewer windings than an electrically conductive coil that also is wound around the delivery device. As a result, in some embodiments, when the coil and the wire are delivered to a target site, the coil may still include some windings, while the wire may be relatively straight. In certain embodiments, a wire that is wound around a delivery device may have some slackness so that the wire does not form a tight coil around the delivery device. In some embodiments, this slackness may limit the likelihood of the wire breaking when the wire is wound around the delivery device.

As a further example, in certain embodiments, a coil may be mechanically detached from a delivery device. For example, a coil may be detached from a delivery device using a cutter, such as a cutter that can be actuated to detach a coil from a delivery device. As an example, an actuated cutter may slide between a sheath and an inner member of a delivery device, and/or along the surface of a tubular member of a delivery device, to detach a coil from the delivery device. In some embodiments, a coil can be latched onto a delivery device (e.g., an inner member of a delivery device), and can be detached from the delivery device by being unlatched from the delivery device.

In some embodiments, a release wire can be used to mechanically detach a coil from a delivery device. As an example, FIGS. 11A and 11B show a delivery device 360 and an electrically conductive coil 362 and a wire 364 wrapped around delivery device 360. Wire 364 is connected to coil 362. Coil 362 and wire 364 are held onto delivery device 360 by two loops 366 and 368 that wrap around wire 364 and through holes 370, 372, 374, and 376 in delivery device 360. Loops 366 and 368 are connected to a release wire 378. Loop 366 has a weak region 380, and loop 368 has a weak region 382. When release wire 378 is pulled in the direction of arrow A5, weak regions 380 and 382 of loops 366 and 368 can break, so that loops 366 and 368 no longer restrain coil 362 and wire 364 on delivery device 360. Coil 362 and wire 364 can then be delivered to a target site. As another example, FIG. 12 shows a balloon 900 of a delivery device. A wire 902 is looped around balloon 900 such that it forms pairs of overlapping loops, including loops 904 and 906, and loops 908 and 910. A release wire 909 is threaded between the loops to help restrain the looped wire 902 against balloon 900. A third wire 912 connects one end 914 of looped wire 902 to another end 916 of looped wire 902, and includes a capacitor 918. During use, release wire 909 is withdrawn, thereby separating the pairs of overlapping loops from each other. Wire 902, which can have shape memory of a coil, can then expand to form that coil. Together with wire 912, wire 902 can, for example, form a resonance circuit during use.

As a further example, in some embodiments, a coil may be detached from a delivery device by exposing the coil to ultrasound. The ultrasound may cause one or more points of attachment between the coil and the delivery device to break, thereby causing the coil to become detached from the delivery device in at least one region.

In some embodiments, an operator can detach a coil from a delivery device at a desired time (e.g., by mechanically and/or electrolytically detaching the coil from the delivery device).

As an additional example, while the delivery of a stent into the entirety of an electrically conductive coil has been shown, in certain embodiments, a stent may be delivered into only a portion of an electrically conductive coil.

As another example, in some embodiments, only a portion of a stent may be delivered into an electrically conductive coil. For example, one end of a stent may be delivered into an electrically conductive coil, while another end of the stent is not delivered into the electrically conductive coil.

As a further example, in some embodiments, an electrically conductive coil can be restrained by a sheath that does not include grooves on its interior surface. For example, FIGS. 13A-13C illustrate a method of delivering a coil 400 into a lumen 402 of a subject. As shown in FIG. 13A, a delivery system 404 includes a generally tubular inner member 406, a tip 408 at the distal end 410 of inner member 406, and a sheath 412 surrounding inner member 406. Sheath 412 has an interior surface 414 and an exterior surface 416. On its interior surface 414, sheath 412 does not have any grooves. Sheath 412 restrains coil 400. As shown in FIGS. 13A-13C, coil 400 has a proximal end 401, a distal end 403, and a wire 405 connecting proximal end 401 to distal end 403. Wire 405 coils around inner member 406.

As shown in FIG. 13B, to deliver coil 400 into lumen 402, sheath 412 is withdrawn proximally (in the direction of arrow A6). As sheath 412 is withdrawn, coil 400 exits sheath 412 and expands into lumen 402. As coil 400 expands into lumen 402, the total number of windings of coil 400 decreases, and wire 405 straightens. Eventually, the entirety of coil 400 is delivered into lumen 402, and delivery system 404 is removed from lumen 402, leaving expanded coil 400, which has a lumen 420, within lumen 402 (FIG. 13C). In some embodiments, after coil 400 has been delivered into lumen 402, a stent can be delivered into lumen 420 of coil 400.

As an additional example, in some embodiments, a coil may be attached to a delivery device by at least two bioerodible connectors (e.g., two bioerodible strips) having different thicknesses. The bioerodible connectors may be formed of the same bioerodible material(s) or of different bioerodible material(s). In certain embodiments, the difference in thickness between bioerodible connectors can result in one portion of the coil (e.g., a distal portion) being released by one of the bioerodible connectors before another portion of the coil (e.g., a proximal portion) is released by the other bioerodible connector.

As another example, in some embodiments, a coil can be restrained during delivery using a combination of the above-described systems. For example, in certain embodiments, a coil can be both restrained within a sheath and attached to a delivery device (e.g., using one or more bioerodible connectors).

As an additional example, in some embodiments, one or more capacitive elements and/or conductive elements can be formed in a layer-by-layer construction. Examples of conductive elements include electrically conductive coils and electrically conductive traces (e.g., that are used to interconnect electrically conductive coils and capacitive elements). Layer-by-layer deposition methods can include coating a substrate material with charged species via electrostatic self-assembly. In some embodiments, a layer-by-layer deposition method can include using sequential steps to provide multilayer growth on a substrate material (e.g., with intermittent rinsing between steps). During the deposition method, the substrate material can be exposed to one or more solutions and/or suspensions of cationic and anionic species. The multilayer growth can occur by depositing or adsorbing a first layer having a first surface charge on the substrate material, then depositing a second layer on the first layer, the second layer having a second surface charge that is the opposite of the first surface charge, and repeating these steps until a desired number of layers has been formed on the substrate material.

In certain embodiments, a multilayer conductive element and/or a multilayer capacitive element can include multiple polyelectrolyte layers including at least one type of polyelectrolyte as a charged species, and/or multiple particle layers including at least one type of charged particle as a charged species. Particles can include, for example, carbon, one or more metals (e.g., gold, platinum, palladium, iridium, osmium, rhodium, titanium, tantalum, tungsten, ruthenium, magnesium, iron), metal alloys (e.g., stainless steel, Nitinol, cobalt-chromium alloys), and/or ceramics. In some embodiments, particles can include alloys of magnesium and/or iron (e.g., including cerium, calcium, zinc, zirconium, and/or lithium). In certain embodiments, particles can include alumina, titanium oxide, tungsten oxide, tantalum oxide, zirconium oxide, and/or silica. Other examples of materials that can be used in particles include silicates (e.g., aluminum silicate, polyhedral oligomeric silsequioxanes (POSS)), phyllosilicates (e.g., clays and/or micas, such as montmorillonite, hectorite, hydrotalcite, vermiculite, and/or laponite), particulate molecules (e.g., dendrimers), polyoxometallates, fullerenes, and nanotubes (e.g., single-wall nanotubes, multi-wall carbon nanotubes).

Particles are described, for example, in U.S. patent application Ser. No. ______ [Attorney Docket No. 05-01440], filed concurrently herewith and entitled “Medical Devices Having Electrical Circuits With Multilayer Regions”. Polyelectrolytes are described, for example, in Weber, U.S. Patent Application Publication No. US 2005/0261760 A1, published on Nov. 24, 2005, and entitled “Medical Devices and Methods of Making the Same”; Weber et al., U.S. Patent Application Publication No. US 2005/0208100 A1, published on Sep. 22, 2005, and entitled “Medical Articles Having Regions With Polyelectrolyte Multilayer Coatings for Regulating Drug Release”; and U.S. patent application Ser. No. ______ [Attorney Docket No. 05-01440], filed concurrently herewith and entitled “Medical Devices Having Electrical Circuits With Multilayer Regions”.

In certain embodiments, a multilayered structure can include at least one conductive layer and at least one insulating layer. The conductive layer can include, for example, metal (e.g., gold) particles. In some embodiments, the conductive layer can be in the form of one or more conductive traces. The conductive layer can, for example, be formed in a coil pattern, and/or can be in the form of wiring that connects electrical components. The insulating layer can include, for example, one or more polymers and/or one or more ceramic materials.

In some embodiments, a multilayered structure can form a resonance circuit. The resonance circuit can be used, for example, to enhance the MRI visibility of material within the lumen of an endoprosthesis, as described above. In certain embodiments, a multilayered structure can include alternating conductive layers and insulating layers. In some embodiments, an insulating multilayered structure can include alternating polyelectrolyte-containing layers. In certain embodiments, a conductive multilayered structure can include alternating conductive-particle-containing layers and polyelectrolyte-containing layers.

In some embodiments, one or more of the conductive layers of a multilayered structure can be relatively thin. For example, in certain embodiments, one or more of the conductive layers of a multilayered structure can have a thickness of at least about 75 nanometers (e.g., at least about 100 nanometers, at least about 150 nanometers, at least about 200 nanometers, at least about 250 nanometers, at least about 300 nanometers, at least about 350 nanometers, at least about 400 nanometers, at least about 450 nanometers) and/or at most about 500 nanometers (e.g., at most about 450 nanometers, at most about 400 nanometers, at most about 350 nanometers, at most about 300 nanometers, at most about 250 nanometers, at most about 200 nanometers, at most about 150 nanometers, at most about 100 nanometers). As the number of conductive layers in a multilayered structure increases, the conductance, and thus the inductance, of the multilayered structure can also increase. As a result, the size of the capacitor used in conjunction with the multilayered structure to form a resonance circuit can decrease.

A layer-by-layer assembly process can include, for example, encapsulating conductive particles (e.g., metal particles such as gold (Au) nanoparticles) in polyelectrolyte (e.g., poly(diallyldimethylammonium chloride) (PDDA), to form positively charged gold particles. A substrate can then be exposed to a colloidal dispersion of the charged particles (e.g., PDDA-coated gold particles), rinsed, exposed to an oppositely charged polyelectrolyte (e.g., a solution of poly s-119 from Sigma), rinsed, exposed to a colloidal dispersion of charged particles, rinsed, exposed to oppositely charged polyelectrolyte, rinsed, and so forth, until the desired number of layers have been deposited on the substrate.

With respect to capacitive elements, in some embodiments, layer-by-layer assembly techniques, such as those described in Liu et al., “Layer-By-Layer Ionic Self-Assembly of Au Colloids Into Multilayer Thin-Films With Bulk Metal Conductivity”, Chemical Physics Letters 298 (1998) 315-319, can be used to form capacitor plates. A specific example of a technique for layer-by-layer assembly of dielectric layers of good resistivity, which may be positioned between the capacitor plates, is discussed in A. A. Antipov et al., Advances in Colloid and Interface Science 111 (2004) 49-61, and in references cited therein. In this technique, layer-by-layer-deposited poly(acrylic acid)(PAA)-poly(allylamine hydrochloride)(PAH) multilayer films are crosslinked via heat-induced amidation. In certain embodiments, hydrophobic multilayers can be employed as dielectric films. (See, e.g., R. M. Jisr et al., “Hydrophobic and Ultrahydrophobic Multilayer Thin Films from Perfluorinated Polyelectrolytes,” Angew. Chem. Int. Ed. 2005, 44, 782-785.)

Layer-by-layer assembly of multilayered structures (e.g., multilayered structures including conductive structures including metal particles) is described, for example, in Liu et al., “Layer-By-Layer Ionic Self-Assembly of Au Colloids Into Multilayer Thin-Films With Bulk Metal Conductivity”, Chemical Physics Letters 298 (1998) 315-319; and in U.S. patent application Ser. No. ______ [Attorney Docket No. 05-01440], filed concurrently herewith and entitled “Medical Devices Having Electrical Circuits With Multilayer Regions”.

As a further example, in some embodiments, a coil, a stent, and/or a delivery device can include one or more releasable therapeutic agents, drugs, or pharmaceutically active compounds, such as anti-thrombogenic agents, antioxidants, anti-inflammatory agents, anesthetic agents, anti-coagulants, and antibiotics. In certain embodiments, the therapeutic agents, drugs, or pharmaceutically active compounds may be disposed in a coating on the coil, stent, and/or delivery device. In some embodiments in which a coil is attached to a delivery device using one or more bioerodible materials, the bioerodible material(s) can include one or more therapeutic agents, drugs, or pharmaceutically active compounds. Therapeutic agents, drugs, and pharmaceutically active compounds are described, for example, in Phan et al., U.S. Pat. No. 5,674,242; Weber, U.S. Pat. No. 6,517,888; Zhong et al., U.S. Patent Application Publication No. US 2003/0003220 A1, published on Jan. 2, 2003; and Lanphere et al., U.S. Patent Application Publication No. US 2003/0185895 A1, published on Oct. 2, 2003.

As an additional example, while stents have been described, in some embodiments, an electrically conductive coil can be used in conjunction with one or more other types of medical devices. Examples of medical devices include other types of endoprostheses, such as stent-grafts, covered stents, and grafts. Grafts can be artificial grafts (e.g., formed of polytetrafluoroethylene (PTFE) and/or polyethylene terephthalate (PET)), and/or can be formed of autologous tissue (e.g., vein grafts). Other examples of medical devices include filter devices; tissue-engineered vessels, valves, and organs; vena cava filters; valves (e.g., aortic valves); and abdominal aortic aneurysm (AAA) devices (e.g., AAA stents, AAA grafts). In some embodiments, tissue-engineered vessels, valves, and/or organs can be formed on a metal support, such as an electrically conductive coil. The electrically conductive coil can both provide support to the tissue-engineered vessel, valve, or organ, and enhance the visibility (e.g., by enhancing the resolution) of tissue under MRI. Thus, MRI can be used, for example, to monitor neo-intima formation and/or the build-up of soft tissue (e.g., plaque). In certain embodiments, MRI can be used to monitor the urological system and/or the reproductive system.

As a further example, in some embodiments, a coil and a stent can be delivered to a target site (e.g., in a lumen of a subject) using the same delivery device. The coil and the stent can be delivered simultaneously, or at different times. As an example, a stent can be loaded onto a balloon of a balloon catheter, and an electrically conductive coil can be loaded over at least a portion of the stent. The balloon catheter can then be delivered to a target site, where the balloon can be expanded to deliver both the stent and the coil into the target site. As another example, a balloon catheter upon which a stent and an electrically conductive coil are loaded can be delivered to a target site, and the coil can then be expanded into the target site. Thereafter, the stent can be expanded into the target site. For example, FIG. 14A shows a delivery device 500 disposed within a lumen 502. At its distal end 508, delivery device 500 includes a balloon 506. A stent 504 is crimped onto balloon 506, and a self-expanding electrically conductive coil 510 is tightly wound around stent 504. Coil 510 has a proximal end 512 and a distal end 516 that are connected to each other by a wire 513. At its proximal end 512, coil 510 is attached to stent 504 by a bioerodible connector 514, and at its distal end 516, coil 510 is attached to stent 504 by a bioerodible connector 517. When bioerodible connector 514 erodes, and delivery device 500 is rotated in the direction of arrow A7, coil 510 is delivered into lumen 502, as shown in FIG. 14B. The rotation of coil 510 during delivery causes wire 513 to rotate and form a coil as well. As coil 510 is being delivered into lumen 502 and/or after coil 510 has been delivered into lumen 502, bioerodible connector 517 can also erode, causing coil 510 to become completely detached from stent 504. After coil 510 has been delivered into lumen 502 and/or detached from stent 504, stent 504 is expanded into lumen 502 (e.g., by inflating balloon 506).

As an additional example, in certain embodiments, a balloon-expandable stent can be loaded onto a balloon of a balloon catheter, and a self-expanding electrically conductive coil can be loaded onto the balloon, over the balloon-expandable stent. The balloon can be inflated, delivering both the stent and the coil into the target site.

As a further example, in some embodiments, an electrically conductive coil can be delivered to a target site using a balloon catheter, and a stent can be delivered into a lumen of the electrically conductive coil using a different delivery system (e.g., a different balloon catheter).

As another example, in some embodiments, an electrically conductive coil can be wound onto a delivery device at an angle. In certain embodiments, the coil can be wound onto the delivery device manually and/or using a winding system. An example of a winding system is the 310-LC Hand Winder from George Stevens Manufacturing Inc. (Bensenville, Ill.). In some embodiments, a polymer sleeve can be mounted over a mandrel of a winding system, and a coil can then be wound around the polymer sleeve. In certain embodiments, a coil can be loaded onto a delivery device by forming the coil at a desired expanded diameter, and then angling the coil and loading the angled coil onto the delivery device. As an angled coil is delivered into a target site, the coil can straighten into the target site, thereby causing the angle to decrease. For example, FIG. 15A shows a delivery device 550 disposed within a lumen 552. Delivery device 550 has a longitudinal axis LA1, and includes a balloon 557. An electrically conductive coil 554 is wound onto balloon 557, which has a diameter d when uninflated. Coil 554 is wound onto balloon 557 at an angle α measured relative to an axis PA1 that is perpendicular to longitudinal axis LA1. Coil 554 has an end 551 and an end 553 that are connected to each other by a wire 555, and is attached to delivery device 550 by bioerodible connectors 556, 558, 560, and 562. As shown in FIG. 15B, when bioerodible connectors 556, 558, 560, and 562 erode and balloon 557 is inflated to a diameter D, coil 554 straightens out, filling lumen 552. Thereafter, and as shown in FIG. 15C, delivery device 550 is withdrawn proximally from coil 554, leaving coil 554 within lumen 552. As shown in FIGS. 15A-15C, coil 554 has the same number of windings throughout the delivery process.

FIG. 15D shows an enlarged view of a portion of delivery device 550, prior to inflation of balloon 557 and delivery of coil 554, and more specifically shows just one section of a winding 564 of coil 554. As shown in FIG. 15D, winding 564 forms an elliptical curve that, if continued to completion, would form an ellipse E (shown partially in phantom) having a minor axis “a” and a major axis “b”. In some embodiments, angle α of coil 554 relative to axis PA1 prior to inflation of balloon 557 can be selected according to equation (1) below:
(d 2)/(D 2)=sin(α)  (1)
When coil 554 is wound at angle α according to the above equation, coil 554 can fill lumen 552 after balloon 557 has been expanded to diameter D, and can have the same number of windings in its expanded configuration as in its unexpanded configuration.

As an additional example, in some embodiments, an angled coil can remain angled when delivered into a target site. For example, in certain embodiments, an angled coil (e.g., formed out of a shape-memory material) may be used in an aorta. Without wishing to be bound by theory, it is believed that by being angled, the coil may have an enhanced ability to amplify the RF field that is generated by an MRI system, when the coil is being delivered into the aorta. For example, the aorta may be aligned along the main axis of the MRI system. By being angled, the coil may not be disposed at a perpendicular angle relative to the RF waves generated by the MRI system, and may have an enhanced ability to function as a receiver of the RF waves. This enhanced ability to function as a receiver of the RF waves can cause the coil also to exhibit an enhanced ability to amplify the RF field.

As another example, in certain embodiments, a coil can include windings having bent regions prior to expansion of the coil into a target site. When the coil is delivered into a target site, the bent regions can straighten, allowing the coil to fill the target site. For example, FIG. 16A shows a delivery device 600 disposed within a lumen 602 and including a balloon 603 supporting an electrically conductive coil 604. A wire 605 connects one end 607 of coil 604 to another end 609 of coil 604. As shown in FIG. 16A, in its unexpanded form, coil 604 has windings 606 including loop-shaped bent regions 608. Each bent region 608 restrains its neighboring bent region 608, thereby helping to maintain coil 604 on balloon 603. Referring now to FIG. 16B, when balloon 603 is inflated, bent regions 608 straighten and coil 604 straightens into lumen 602. As shown in FIGS. 16A and 16B, coil 604 has the same number of windings 606 in its unexpanded form as it has in its expanded form.

Coil 604 can, for example, be formed of a metal. In some embodiments, coil 604 can be formed of a relatively malleable metal, such as gold. This malleability can result in relatively easy formation of coil 604 (e.g., bent regions 608). In certain embodiments, coil 604 can be formed by bending a wire to form bent regions 608, and then winding the wire into the shape of coil 604. While bent regions 608 of coil 604 overlap with their neighboring bent regions 608, in some embodiments, a coil can include bent regions that do not substantially contact each other. In certain embodiments, the bent regions of a coil may be parallel to each other but may not overlap with each other. In some embodiments, the bent regions of a coil can partially overlap with each other. In certain embodiments, a bent region of a coil can be nested within a neighboring bent region of the coil (e.g., when the coil is loaded onto a delivery device).

While a coil with windings including bent regions pointing in the same direction has been described, in some embodiments, a coil can include windings with bent regions pointing in different directions. For example, FIG. 17 shows an electrically conductive coil 650 disposed on a balloon 652 of a delivery device 654 that has been delivered into a lumen 656. Coil 650 includes windings 658 having loop-shaped bent regions 660 pointing in one direction, and windings 662 having loop-shaped bent regions 664 pointing in the opposite direction.

While coils including windings with loop-shaped bent regions have been described, in certain embodiments, a coil can include one or more windings with bent regions of a different shape. For example, FIG. 18 shows an electrically conductive coil 680 disposed on a balloon 682 of a delivery device 684 that has been delivered into a lumen 686. Coil 680 includes windings 688 having triangular bent regions 690.

In certain embodiments, a coil can include windings with bent regions that have different shapes and/or that are formed in different directions.

As a further example, in some embodiments, an electrically conductive coil can include an adjustable wire that can adjust to connect two ends of the coil to each other during and/or after delivery of the coil to a target site. For example, FIG. 19A shows a delivery device 700 disposed within a lumen 702 of a subject. An electrically conductive coil 704 including windings 706 and a stopper 701 is disposed on delivery device 700. Coil 704 also includes a wire 708 having one end 710 that is integrally formed with coil 704, and another end 714 that includes a loop 712. Loop 712 is disposed around a winding 706 of coil 704. Two bioerodible connectors 716 and 718 connect coil 704 to delivery device 700. As shown in FIG. 19B, when bioerodible connectors 716 and 718 erode, coil 704 unwinds off of delivery device 700, filling lumen 702. During the unwinding of coil 704, windings 706 unwind through loop 712, until loop 712 is stopped by stopper 701. As shown in FIG. 19C, after coil 704 has been delivered into lumen 702, delivery device 700 can be withdrawn from lumen 702, leaving coil 704 disposed within lumen 702.

As an additional example, in some embodiments, an electrically conductive coil can be formed out of a wire that itself is formed out of a coil. For example, FIG. 20 shows an electrically conductive coil 750 that is formed out of a coiled wire 752. Because wire 752 is coiled, coil 750 can stretch (e.g., during expansion of coil 750 into a target site using a delivery device). Wire 752 can be formed of, for example, one or more metals, such as platinum and/or gold. In some embodiments, the material of wire 752 can be selected for malleability and/or for sufficient strength so that coil 750 can maintain its expanded shape at a target site. In certain embodiments, coil 750 and an endoprosthesis can be delivered into a target site (e.g., a lumen) simultaneously (e.g., using a balloon catheter).

As a further example, in some embodiments, an electrically conductive coil can include a polymeric coil body that is at least partially coated with an electrically conductive material. For example, the polymeric coil body can be imprinted with an electrically conductive ink. The ink can be used to form a layer that is, for example, at least about two millimeters thick and/or at most about four millimeters thick. In certain embodiments, at least one of the components of a resonance circuit can be formed of a polymer that is imprinted with an electrically conductive ink. For example, a resonance circuit may include a coil formed out of Nitinol, and a capacitor formed out of a polymer imprinted with an electrically conductive ink.

As an additional example, a wire connecting the ends of an electrically conductive coil can extend within the lumen of the coil and/or outside of the lumen of the coil. For example, FIG. 21 shows an electrically conductive coil 800 having a lumen 802. A wire 804 connects one end 806 of coil 800 to another end 808 of coil 800. Wire 804 does not extend through lumen 802 of coil 800. FIG. 22 shows an electrically conductive coil 850 having a lumen 852. A wire 854 connects one end 856 of coil 850 to another end 858 of coil 850. Wire 854 extends through lumen 852 of coil 850.

As another example, in some embodiments, an electrically conductive coil can include two ends that are connected to each other by a coiled wire. In certain embodiments, when the electrically conductive coil is delivered into a target site, the wire can uncoil until it is straight, and then can coil in a direction that is opposite to the direction in which the wire was originally coiled.

As an additional example, while coil delivery devices including sheaths have been described, in some embodiments, a coil delivery device can include a rolling membrane. Rolling membranes are described, for example, in Austin et al., U.S. Patent Application Publication No. US 2004/0199239 A1, published on Oct. 7, 2004, and entitled “Protective Loading of Stents”, and in Vrba et al., U.S. Pat. No. 6,942,682.

As another example, in some embodiments, an electrically conductive coil can function as an imaging coil and as a resonance circuit. For example, during delivery of the coil, and while the coil is disposed on a delivery device (e.g., a catheter), the coil can be used to provide an image of its environment under magnetic resonance imaging (MRI). The close proximity of the coil to the area that is being imaged can allow the area to be imaged with relatively high resolution. Once the coil has been delivered into a target site, the coil can be used as a resonance circuit (e.g., that can enhance the visibility of material within the lumen of an endoprosthesis at the target site). As an example, FIG. 23A shows an electrically conductive coil 950 (e.g., formed of a coiled wire, as described above) that is disposed on the balloon 952 of a catheter 954. As shown in FIG. 23A, catheter 954 has been delivered into a lumen 955. A wire 956 connects one end 958 of coil 950 to another end 960 of coil 950. One winding 962 of coil 950 includes a capacitor 964. Catheter 954 includes a shaft 966. Two electrically conductive traces 968 and 970 (e.g., formed of sputtered gold) are located both on shaft 966 and on balloon 952 of catheter 954. A second capacitor 972 is mounted onto shaft 966. Prior to delivery of coil 950 into lumen 955 (FIG. 23A), winding 962 of coil 950 contacts traces 968 and 970, thereby forming a circuit that includes capacitors 964 and 972. During this time, coil 950 can be used to image the environment around it under MRI. For example, an electrical current can be flowed through gold traces 964 and 972, and coil 950 can function as an RF transmitter. In some embodiments, a 1.5 Tesla or 3.5 Tesla MRI system can be used in conjunction with coil 950 when coil 950 is functioning as an imaging coil.

During delivery of coil 950, balloon 952 is inflated to deliver coil 950 into lumen 955. Thereafter, and as shown in FIG. 23B, balloon 952 is deflated and withdrawn, leaving coil 950 disposed within lumen 955. When balloon 952 is withdrawn, coil 950 is no longer part of a circuit that includes both capacitor 964 and capacitor 972. Rather, coil 950 forms a resonance circuit including capacitor 964. At this point, coil 950 can be used as a resonance circuit, for example, to image the material within a lumen of an endoprosthesis that can also be delivered into lumen 955.

As shown in FIGS. 23A and 23B, coil 950 has a larger diameter (and thus, a larger cross-sectional area) after coil 950 has been delivered into lumen 955, as compared to the diameter of coil 950 prior to delivery. The inductance of a coil such as coil 950 depends on the cross-sectional area of the coil, as shown in equation (2) below, in which N=number of windings of the coil, μ=magnetic permeability of the medium surrounding the coil, A=cross-sectional area of the coil, and 1=length of the coil:
L=(μN 2 A)/(1)  (2)

The resonance frequency ωO of a coil such as coil 950 is determined based on the inductance and the capacitance, as shown in equation (3) below:
ωO=1/√(LC)  (3)

Thus, the overall capacitance of a coil can be manipulated to maintain the resonance frequency of the coil during use and delivery. Accordingly, as shown in FIGS. 23A and 23B above, when coil 950 is being used as an imaging coil and has a relatively small cross-sectional area, coil 950 is part of a circuit including two capacitors. However, when coil 950 has been delivered into lumen 955 and has a larger cross-sectional area, the larger cross-sectional area increases the inductance of coil 950. Thus, to maintain the resonance frequency of coil 950, coil 950 only forms a circuit with one capacitor (capacitor 964).

While FIG. 23A shows capacitor 972 mounted on catheter shaft 966, in some embodiments, a second capacitor can be located elsewhere. As an example, in certain embodiments, a second capacitor may be located externally relative to the body, but may be connected to the coil by two lead wires. As another example, in some embodiments, an electrically conductive coil including a capacitor can be delivered to a target site using a delivery system including a generally tubular inner member and a sheath surrounding the inner member. The coil can be loaded into the delivery device such that the capacitor on the coil is located by the distal section of the sheath. The sheath can include a second capacitor that is mounted on the exterior surface of the sheath. The capacitor can include flat strips (e.g., two flat strips) that are embedded in and/or attached to the exterior surface of the sheath (e.g., glued to the sheath), but that also protrude to a certain extent past the distal end of the sheath (e.g., by about two millimeters). When the compressed coil is inserted into the sheath as the coil is being loaded into the delivery device, the two flaps of the second capacitor can be folded around into the interior surface of the sheath. The flaps can contact the coil when the coil is disposed within the sheath. This can allow the coil to be used as an imaging coil during delivery to a target site, and to function as a resonance circuit once the coil has been delivered into the target site. The use of a catheter coil for high-resolution MRI imaging is described, for example, in Zimmermann-Paul et al., “High-Resolution Intravascular Magnetic Resonance Imaging: Monitoring of Plaque Formation in Heritable Hyperlipidemic Rabbits”, Circulation (Mar. 2, 1999), pages 1054-1061.

While maintenance of the resonance frequency of a coil by adjusting the capacitance of the coil has been described, in some embodiments, the resonance frequency of a coil can be adjusted by changing the magnetic permeability of the environment around the coil. For example, a catheter that is used to deliver the coil may include ferromagnetic material, which can increase the magnetic permeability of the environment around the coil prior to expansion of the coil. This increase in magnetic permeability can result in an increase in the inductance of the coil prior to expansion of the coil. Ferromagnetic materials are described, for example, in Rioux et al., U.S. Patent Application Publication No. US 2004/0101564 A1, published on May 27, 2004, and entitled “Embolization”.

In certain embodiments, an electrically conductive coil that is being used as an imaging coil can be disposed on a delivery device at an angle (e.g., as described above with respect to FIGS. 15A-15D). This can, for example, help the coil to form a relatively comprehensive image of a vessel wall.

As an additional example, in some embodiments, an angled electrically conductive coil can be retained on a delivery device by a sleeve and/or a polymer wire. The sleeve and/or polymer wire can help the coil to retain its angled shape during delivery of the coil to a target site.

For example, in certain embodiments, one or more polymer wires can be disposed between the balloon of a delivery device and an angled coil that is supported by the balloon. As an example, FIG. 24 shows a cross-sectional view of a balloon 1000 that is disposed around an inner member 1002 of a balloon catheter, and that supports an angled electrically conductive coil 1004. As shown, balloon 1000 is in its deflated condition, and includes three folded regions 1006, 1008, and 1010. Polymer wires 1012, 1014, and 1016 are positioned by folded regions 1006, 1008, and 1010 of balloon 1000, respectively. Electrically conductive coil 1004 is wrapped around balloon 1000 such that electrically conductive coil 1004 contacts polymer wires 1012, 1014, and 1016. Additionally, a sleeve 1018 is disposed around coil 1004.

In some embodiments, polymer wires 1012, 1014, and/or 1016 can be relatively soft. For example, polymer wires 1012, 1014, and/or 1016 may be formed of Tecothane® 75A polyether-based polyurethane (from Noveon, Inc., Akron, Ohio). In certain embodiments in which polymer wires 1012, 1014, and/or 1016 are relatively soft, coil 1004 can become at least partially embedded in polymer wires 1012, 1014, and/or 1016. This embedding can cause coil 1004 to experience enhanced retention on balloon 1000, and/or can help coil 1004 to maintain its angled shape during delivery to a target site in a body of a subject.

In certain embodiments, polymer wires 1012, 1014, and/or 1016 can include a core that is formed of a relatively hard polymer, surrounded by a sleeve that is formed of a relatively soft polymer. This, can, for example, limit the likelihood of polymer wires 1012, 1014, and/or 1016 compressing axially. For example, in some embodiments, polymer wires 1012, 1014, and/or 1016 can include a core that is formed of Tecothane® 70D polyether-based polyurethane (from Noveon, Inc., Akron, Ohio), surrounded by a sleeve that is formed of Tecothane® 75A polyether-based polyurethane (from Noveon, Inc., Akron, Ohio).

Polymer wires 1012, 1014, and/or 1016 can have a cross-sectional outer diameter of about 200 microns. In some embodiments in which polymer wires 1012, 1014, and/or 1016 include a core surrounded by a sleeve, the core can have a cross-sectional diameter of about 100 microns.

In certain embodiments, polymer wires 1012, 1014, and/or 1016 can have a textured outer surface. This can, for example, allow coil 1004 to become at least partially embedded in polymer wires 1012, 1014, and/or 1016, and to thereby experience enhanced retention on balloon 1000.

Sleeve 1018, which is disposed around coil 1004, can help to limit the likelihood of coil 1004 expanding prematurely (e.g., during delivery to a target site). In some embodiments, sleeve 1018 can include (e.g., can be formed of) polytetrafluoroethylene (e.g., Teflon® polymer, from DuPont) and/or high-density polyethylene (HDPE). During delivery of coil 1004, sleeve 1018 can be retracted proximally to expose coil 1004. In some embodiments, the friction between coil 1004 and polymer wires 1012, 1014, and/or 1016 can limit the likelihood of sleeve 1018 disturbing the position and/or angle of coil 1004 as sleeve 1018 is retracted proximally. In certain embodiments, at least one of polymer wires 1012, 1014, and 1016 can be connected to balloon 1000. For example, in some embodiments, at least one of polymer wires 1012, 1014, and 1016 can be connected to a polymer ring that, in turn, is connected to a proximal section of balloon 1000. This connection between balloon 1000 and polymer wires 1012, 1014, and/or 1016 can cause polymer wires 1012, 1014, and/or 1016 to be removed with balloon 1000 when balloon 1000 is removed from a target site (e.g., after coil 1004 has been delivered into the target site).

As a further example, in certain embodiments, an angled electrically conductive coil can be retained on a delivery device by a tube and/or a sleeve. The tube and/or sleeve can help the coil to retain its angled shape during delivery of the coil to a target site.

For example, in some embodiments, a soft polymer tube (e.g., formed of Tecothane® 75A polyether-based polyurethane (from Noveon, Inc., Akron, Ohio)) can be extruded and expanded (e.g., by being disposed in toluene). In certain embodiments, one or more slits can then be added along the central portion of the tube, without adding slits to either end of the tube. The tube can then be slid over a folded balloon (e.g., of a balloon catheter), an electrically conductive coil can be wound around the tube at an angle, and a sleeve (e.g., formed of a polymer) can be disposed over the angled coil. The coil can then be delivered to a target site in a body of a subject by proximally retracting the sleeve to expose the coil, and inflating the balloon. In some embodiments, the friction between the coil and the tube can limit or prevent the sleeve from disturbing the position and/or angle of the coil as the sleeve is retracted proximally.

As another example, in some embodiments, the distance between at least two windings of an electrically conductive coil can be temporarily maintained (e.g., during delivery of the coil to a target site) using, for example, an erodible material such as gelatin.

As an additional example, in certain embodiments, a stent can be coated with an insulating material and the insulating material can in turn be imprinted with an electrically conductive ink in the pattern of a coil. For example, a stent may be coated with a thin ceramic coating, and an electrically conductive coil may be imprinted upon the ceramic coating. The ceramic coating can be applied to the stent using, for example, physical vapor deposition, and/or can be formed using, for example, a sol-gel process.

All publications, applications, references, and patents referred to in this application are herein incorporated by reference in their entirety.

Other embodiments are within the claims.

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Classifications
U.S. Classification623/1.34
International ClassificationA61F2/82
Cooperative ClassificationA61F2/82, A61B2019/5458, A61F2250/0045
European ClassificationA61F2/82
Legal Events
DateCodeEventDescription
May 22, 2006ASAssignment
Owner name: BOSTON SCIENTIFIC SCIMED, INC., MINNESOTA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WEBER, JAN;SOGARD, DAVID J.;FRIESEN, DAVID L.;AND OTHERS;REEL/FRAME:017662/0130;SIGNING DATES FROM 20060215 TO 20060301