U.S. patent application number 11/388090 was filed with the patent office on 2007-02-08 for medical devices.
Invention is credited to John Blix, David L. Friesen, David J. Sogard, Jan Weber.
Application Number | 20070032862 11/388090 |
Document ID | / |
Family ID | 36593061 |
Filed Date | 2007-02-08 |
United States Patent
Application |
20070032862 |
Kind Code |
A1 |
Weber; Jan ; et al. |
February 8, 2007 |
Medical devices
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.
Inventors: |
Weber; Jan; (Maple Grove,
MN) ; Sogard; David J.; (Edina, MN) ; Friesen;
David L.; (Otsego, MN) ; Blix; John; (Maple
Grove, MN) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Family ID: |
36593061 |
Appl. No.: |
11/388090 |
Filed: |
March 22, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11198961 |
Aug 8, 2005 |
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11388090 |
Mar 22, 2006 |
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Current U.S.
Class: |
623/1.34 |
Current CPC
Class: |
A61B 2090/3958 20160201;
A61F 2250/0045 20130101; A61F 2/82 20130101 |
Class at
Publication: |
623/001.34 |
International
Class: |
A61F 2/06 20060101
A61F002/06 |
Claims
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
[0001] This application is a continuation-in-part of, and claims
priority under 35 U.S.C. .sctn. 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
[0002] The invention relates to medical devices, and to related
components and methods.
BACKGROUND
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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
[0007] 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.
[0008] Embodiments can include one or more of the following
features.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] The method can include expanding the endoprosthesis and/or
viewing the endoprosthesis using magnetic resonance imaging.
[0016] 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).
[0017] 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.
[0018] The electrically conductive coil can be a self-expanding
coil and/or a balloon-expandable coil.
[0019] 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.
[0020] Embodiments may include one or more of the following
advantages.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] Other aspects, features, and advantages are in the
description, drawings, and claims.
DESCRIPTION OF DRAWINGS
[0027] 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.
[0028] FIG. 2 is a perspective view of the endoprosthesis of FIG.
1.
[0029] FIG. 3 is a side view of the electrically conductive coil of
FIG. 1.
[0030] FIG. 4 is a schematic illustration of an embodiment of a
resonance circuit.
[0031] FIG. 5A is an illustration of a embodiment of a coil
delivery system within a lumen of a subject.
[0032] 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.
[0033] 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.
[0034] FIG. 5E is an illustration of an embodiment of an
endoprosthesis disposed within the electrically conductive coil of
FIGS. 5B-5D.
[0035] FIG. 6A is an illustration of an embodiment of a coil
delivery system within a lumen of a subject.
[0036] FIG. 6B is an enlarged view of region 6B of FIG. 6A.
[0037] 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.
[0038] 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.
[0039] FIG. 6E is an illustration of an embodiment of an
endoprosthesis disposed within the electrically conductive coil of
FIGS. 6C and 6D.
[0040] FIG. 7 is a side perspective view of the electrically
conductive coil of FIGS. 6C-6E.
[0041] FIG. 8A is an illustration of an embodiment of a coil
delivery system within a lumen of a subject.
[0042] 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.
[0043] 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.
[0044] FIG. 8D is an illustration of an embodiment of an
endoprosthesis disposed within the electrically conductive coil of
FIGS. 8B and 8C.
[0045] FIG. 9 is a side perspective view of the electrically
conductive coil of FIGS. 8B-8D.
[0046] FIG. 10 is a side view of an embodiment of a coil delivery
system.
[0047] FIG. 11A is a perspective view of an embodiment of a coil
delivery system.
[0048] FIG. 11B is a cross-sectional view of the coil delivery
system of FIG. 11A, taken along line 11B-11B.
[0049] FIG. 12 is a side perspective view of an embodiment of a
coil delivery system and an embodiment of an electrically
conductive coil.
[0050] FIG. 13A is an illustration of a embodiment of a coil
delivery system within a lumen of a subject.
[0051] 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.
[0052] FIGS. 14A and 14B illustrate the delivery of an embodiment
of an electrically conductive coil into the lumen of a subject.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] FIG. 15D is an enlarged view of a portion of the coil
delivery system and the electrically conductive coil of FIG.
15A.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] 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.
[0064] FIG. 20 is a side view of an embodiment of an electrically
conductive coil.
[0065] FIG. 21 is a side view of an embodiment of an electrically
conductive coil.
[0066] FIG. 22 is a side view of an embodiment of an electrically
conductive coil.
[0067] 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.
[0068] 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.
[0069] 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
[0070] 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.
[0071] 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.
[0072] 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.
[0073] A coil such as coil 10 can be delivered into lumen 12 using
any of a number of different methods.
[0074] 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.
[0075] 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.
[0076] 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.TM. family of balloon catheters (Boston
Scientific Scimed, Inc., Maple Grove, Minn.). Stents and stent
delivery are also exemplified by the Radius.RTM. or Symbiot.RTM.
systems (Boston Scientific Scimed, Inc., Maple Grove, Minn.).
[0077] 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
(C.sub.12H.sub.22O.sub.11), dextrose (C.sub.6H.sub.12O.sub.6),
sorbose (C.sub.6H.sub.12O.sub.6)); sugar derivatives (e.g.,
glucosamine (C.sub.6H.sub.13NO.sub.5), sugar alcohols such as
mannitol (C.sub.6H.sub.14O.sub.6)); inorganic, ionic salts (e.g.,
sodium chloride (NaCl), potassium chloride (KCl), sodium carbonate
(Na.sub.2CO.sub.3)); 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).
[0078] 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".
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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.
[0083] 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.
[0084] 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.
[0085] 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).
[0086] 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.
[0087] 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 (Fe.sub.3Be), iron
platinum (Fe.sub.3Pt), 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.
[0088] 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.
[0089] 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.
[0090] 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 10.sup.7 Ohm-cm). Examples of polymers that can be used
as insulating materials include polyimides, polystyrenes, polyamide
12, polytetrafluoroethylene (Teflon.RTM.), 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 10.sup.11 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.
[0091] 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.
[0092] 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.
[0093] 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.
[0094] 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).
[0095] 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.
[0096] 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).
[0097] 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.times.10.sup.-3 (e.g., less than
0.871.times.10.sup.-3, less than 0.3.times.10.sup.-3, less than
-0.2.times.10.sup.-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".
[0098] 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.
[0099] 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.
[0100] 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).
[0101] 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.times.10.sup.-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.sup.-1 (e.g., at
least 50 cm.sup.-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.
[0102] 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.
[0103] While certain embodiments have been described, other
embodiments are possible.
[0104] 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.
[0105] 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.
[0106] 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.
[0107] 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.
[0108] 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.
[0109] 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.
[0110] 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.
[0111] 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).
[0112] 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.
[0113] 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.
[0114] 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.
[0115] 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.
[0116] 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.
[0117] 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).
[0118] 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.
[0119] 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).
[0120] 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".
[0121] 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.
[0122] 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.
[0123] 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.
[0124] 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.
[0125] 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.)
[0126] 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".
[0127] 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.
[0128] 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.
[0129] 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).
[0130] 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.
[0131] 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).
[0132] 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 .alpha. 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.
[0133] 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 .alpha. of coil 554 relative
to axis PA1 prior to inflation of balloon 557 can be selected
according to equation (1) below: (d.sup.2)/(D.sup.2)=sin(.alpha.)
(1) When coil 554 is wound at angle .alpha. 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.
[0134] 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.
[0135] 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.
[0136] 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).
[0137] 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.
[0138] 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.
[0139] In certain embodiments, a coil can include windings with
bent regions that have different shapes and/or that are formed in
different directions.
[0140] 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.
[0141] 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).
[0142] 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.
[0143] 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.
[0144] 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.
[0145] 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.
[0146] 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.
[0147] 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.
[0148] 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,
.mu.=magnetic permeability of the medium surrounding the coil,
A=cross-sectional area of the coil, and 1=length of the coil:
L=(.mu.N.sup.2A)/(1) (2)
[0149] The resonance frequency .omega..sub.O of a coil such as coil
950 is determined based on the inductance and the capacitance, as
shown in equation (3) below: .omega..sub.O=1/ (LC) (3)
[0150] 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).
[0151] 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.
[0152] 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".
[0153] 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.
[0154] 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.
[0155] 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.
[0156] 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.RTM. 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.
[0157] 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.RTM. 70D polyether-based
polyurethane (from Noveon, Inc., Akron, Ohio), surrounded by a
sleeve that is formed of Tecothane.RTM. 75A polyether-based
polyurethane (from Noveon, Inc., Akron, Ohio).
[0158] 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.
[0159] 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.
[0160] 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.RTM. 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).
[0161] 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.
[0162] For example, in some embodiments, a soft polymer tube (e.g.,
formed of Tecothane.RTM. 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.
[0163] 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.
[0164] 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.
[0165] All publications, applications, references, and patents
referred to in this application are herein incorporated by
reference in their entirety.
[0166] Other embodiments are within the claims.
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