U.S. patent application number 11/828921 was filed with the patent office on 2008-01-24 for mri visible catheter balloon.
This patent application is currently assigned to ADVANCED CARDIOVASCULAR SYSTEMS, INC.. Invention is credited to Jeong S. Lee, Jose A. Romero, Edwin Wang, Roseminda J. White.
Application Number | 20080021495 11/828921 |
Document ID | / |
Family ID | 25499463 |
Filed Date | 2008-01-24 |
United States Patent
Application |
20080021495 |
Kind Code |
A1 |
Lee; Jeong S. ; et
al. |
January 24, 2008 |
MRI VISIBLE CATHETER BALLOON
Abstract
Medical devices or components thereof, and particularly
intracorporeal devices for therapeutic or diagnostic uses, which
are formed at least in part of a polymeric material and a
ferromagnetic or paramagnetic material, so that the medical device
or component thereof is visible on magnetic resonance imaging (MRI)
scans. In one embodiment, the medical device is a balloon catheter
having an MRI visible balloon. In a presently preferred embodiment,
there is an insufficient amount of the ferromagnetic or
paramagnetic material within a wall of the balloon or coated onto a
wall of the balloon to make the balloon radiopaque.
Inventors: |
Lee; Jeong S.; (Diamond Bar,
CA) ; Wang; Edwin; (Tustin, CA) ; White;
Roseminda J.; (Wildomar, CA) ; Romero; Jose A.;
(Perris, CA) |
Correspondence
Address: |
FULWIDER PATTON, LLP (ABBOTT)
6060 CENTER DRIVE
10TH FLOOR
LOS ANGELES
CA
90045
US
|
Assignee: |
ADVANCED CARDIOVASCULAR SYSTEMS,
INC.
P.O. Box 58167
Santa Clara
CA
95052
|
Family ID: |
25499463 |
Appl. No.: |
11/828921 |
Filed: |
July 26, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11094333 |
Mar 29, 2005 |
|
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11828921 |
Jul 26, 2007 |
|
|
|
09957354 |
Sep 19, 2001 |
6911017 |
|
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11094333 |
Mar 29, 2005 |
|
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Current U.S.
Class: |
606/192 |
Current CPC
Class: |
A61L 29/126 20130101;
A61F 2/95 20130101; A61M 25/10 20130101; A61M 25/104 20130101; A61L
29/18 20130101; A61M 2025/1079 20130101; A61B 2090/3954 20160201;
A61M 2025/1075 20130101; A61M 2025/1031 20130101; A61L 29/106
20130101; A61M 25/1029 20130101 |
Class at
Publication: |
606/192 |
International
Class: |
A61M 29/00 20060101
A61M029/00 |
Claims
1.-26. (canceled)
27. A medical device or component thereof comprising a polymeric
material and an amount of ferromagnetic or paramagnetic material
dispersed in the polymeric material, the amount of ferromagnetic or
paramagnetic material being not greater than about 30% by weight of
the dispersion and being sufficient to make the medical device or
component thereof visible under magnetic resonance imaging and
insufficient to make the medical device or component thereof a
radiopaque marker.
28. The medical device of component of claim 27 wherein the amount
of ferromagnetic or paramagnetic material is about 5% to about 20%,
by weight of the polymeric material/ferromagnetic or paramagnetic
material dispersion.
Description
BACKGROUND OF THE INVENTION
[0001] This invention generally relates to medical devices, and
particularly to intracorporeal devices for therapeutic or
diagnostic uses such as balloon catheters, and vascular grafts.
[0002] In percutaneous transluminal coronary angioplasty (PTCA)
procedures, a guiding catheter is advanced until the distal tip of
the guiding catheter is seated in the ostium of a desired coronary
artery. A guidewire, positioned within an inner lumen of a
dilatation catheter, is first advanced out of the distal end of the
guiding catheter into the patient's coronary artery until the
distal end of the guidewire crosses a lesion to be dilated. Then
the dilatation catheter having an inflatable balloon on the distal
portion thereof is advanced into the patient's coronary anatomy,
over the previously introduced guidewire, until the balloon of the
dilatation catheter is properly positioned across the lesion. Once
properly positioned, the dilatation balloon is inflated with fluid
one or more times to a predetermined size at relatively high
pressures (e.g. greater than 8 atmospheres) so that the stenosis is
compressed against the arterial wall and the wall expanded to open
up the passageway. Generally, the inflated diameter of the balloon
is approximately the same diameter as the native diameter of the
body lumen being dilated so as to complete the dilatation but not
overexpand the artery wall. Substantial, uncontrolled expansion of
the balloon against the vessel wall can cause trauma to the vessel
wall. After the balloon is finally deflated, blood flow resumes
through the dilated artery and the dilatation catheter can be
removed therefrom.
[0003] In such angioplasty procedures, there may be restenosis of
the artery, i.e. reformation of the arterial blockage, which
necessitates either another angioplasty procedure, or some other
method of repairing or strengthening the dilated area. To reduce
the restenosis rate and to strengthen the dilated area, physicians
frequently implant a stent inside the artery at the site of the
lesion. Stents may also be used to repair vessels having an intimal
flap or dissection or to generally strengthen a weakened section of
a vessel. Stents are usually delivered to a desired location within
a coronary artery in a contracted condition on a balloon of a
catheter which is similar in many respects to a balloon angioplasty
catheter, and expanded to a larger diameter by expansion of the
balloon. The balloon is deflated to remove the catheter and the
stent left in place within the artery at the site of the dilated
lesion. Stent covers on an inner or an outer surface of the stent
have been used in, for example, the treatment of pseudo-aneurysms
and perforated arteries, and to prevent prolapse of plaque.
Similarly, vascular grafts comprising cylindrical tubes made from
tissue or synthetic materials such as polyester, expanded
polytetrafluoroethylene, and DACRON may be implanted in vessels to
strengthen or repair the vessel, or used in an anastomosis
procedure to connect vessels segments together.
[0004] To facilitate placement of the catheter at the desired
location in the patient's vasculature, X-ray opaque (i.e.,
radiopaque) material is generally provided on conventional
angioplasty catheters so that the physician can view the catheter
under fluoroscopy. The radiopaque material is typically a metal
marker band on the catheter shaft. For example, two marker bands on
the inner tubular member of the shaft are typically provided, to
indicate the proximal end and distal end of the working length of
the balloon. Blending radiopaque material into the polymer matrix
of the catheter components has been suggested as an alternative to
radiopaque marker bands on the catheter shaft. Additionally,
catheters visible to magnetic resonance imaging (MRI), also known
as nuclear magnetic resonance (NMR) imaging systems have been
suggested for use during MRI scans of a patient. MRI scans are used
provide two-dimensional sectional images of a patient's internal
body structures without exposing the patient to harmful
radiation.
[0005] It would be a significant advance to provide catheter
balloon or other medical device or component thereof with improved
visibility within the patient.
SUMMARY OF THE INVENTION
[0006] This invention is directed to medical devices or components
thereof, and particularly intracorporeal devices for therapeutic or
diagnostic uses, which are formed at least in part of a polymeric
material and a ferromagnetic or paramagnetic material, so that the
medical device or component thereof is visible on magnetic
resonance imaging (MRI) scans. In one embodiment, the medical
device is a balloon catheter having an MRI visible balloon. While
discussed below primarily in terms of a catheter balloon, it should
be understood that the invention includes additional MRI visible
medical devices or components thereof, and particularly expandable
or inflatable members.
[0007] In a presently preferred embodiment, the MRI visible
material is a ferromagnetic material, and a presently preferred
ferromagnetic material is iron oxide, due to the ease of
compounding iron oxide in the polymeric balloon material, the
relative ease of dispersing in many types of balloon materials, and
the lack of a magnetic field orientation effect in which the MRI
image varies depending on the orientation of the medical device or
component thereof. Preferably, a background is provided by a
contrast solution within and/or around the balloon, such as the MRI
visible bright/white background of a Gadolinium solution, to
facilitate viewing the ferromagnetic containing balloon. A balloon
with iron oxide present in the balloon wall in a concentration of
about 5% is readily visible as a dark image in a bright background
of a 1:10 Gadolinium contrast solution. A variety of suitable
ferromagnetic materials can be used including iron, nickel and
cobalt, and compounds thereof such as iron oxide, typically in the
form of a fine powder. In one embodiment, the preferred MRI visible
materials have hydrating power (i.e., they are present in a
hydrated state), which facilitates MRI visibility. For example, in
one embodiment, a proton donating fluid at the device or component
is not required in order to produce the MRI image. In an
alternative embodiment, the MRI visible material may be a
paramagnetic material, preferably provided that magnetic field
orientation effects are minimal or nonexistent. In one embodiment,
the paramagnetic material is selected from the group consisting of
dysprosium, gadolinium, chromium, copper, manganese, and vanadium,
and compounds thereof such as dysprosium oxide.
[0008] The MRI visible materials suitable for use in the invention
may be radiopaque in addition to being MRI visible. However, in a
presently preferred embodiment, there is an insufficient amount of
the ferromagnetic or paramagnetic material in or on the balloon
wall to make the balloon radiopaque. The ferromagnetic or
paramagnetic material does not have a disadvantageous effect on the
strength and compliance of the balloon, unlike prior art catheter
balloons in which it was proposed to make the balloon radiopaque by
forming the balloon of a blend of polymeric and radiopaque
materials. Specifically, such prior art catheter balloons would
require a relatively large amount of radiopaque material to make
the balloon radiopaque, which would consequently reduce the
strength and effect the compliance of the balloon. Thus, the
balloon of the invention, unlike prior art balloons, has an amount
of ferromagnetic or paramagnetic material which is sufficient to
make the balloon MRI visible but insufficient to make the balloon
radiopaque, and does not have a radiopaque material (either the
ferromagnetic or paramagnetic material, or a separate radiopaque
material) in sufficient amounts to make the balloon radiopaque.
Consequently, the balloon is MRI visible and is not radiopaque in
use, and the balloon has excellent performance characteristics such
as a relatively high rupture pressure.
[0009] The MRI visible ferromagnetic or paramagnetic material is a
solid, typically with a particle size of about 0.01 to about 50
.mu.m. In one embodiment of the invention, the ferromagnetic or
paramagnetic material is dispersed in the polymeric material,
preferably by compounding the polymeric material with the
ferromagnetic or paramagnetic material. The term compounding should
be understood to refer to a process in which a high concentration
of ingredient(s) is mixed with a specific polymer to form a master
batch. This master batch is then added to resin during extrusion to
obtain a uniform dispersion of a desired concentration. As a
result, the ferromagnetic material is typically located uniformly
throughout the polymeric wall of the balloon as discrete particles
of material. Alternatively, in another embodiment, the
ferromagnetic or paramagnetic material is a coating on a surface of
the polymeric wall of the balloon. The balloon may be a single
layered balloon, or alternatively, may comprise multiple layers, at
least one of which has the ferromagnetic or paramagnetic material
therein or thereon. The multiple layers are preferably coextruded,
although they may alternatively be separately extruded and then
placed together. In one embodiment, the balloon has a first
polymeric layer, and a second polymeric layer coextruded with the
first layer and containing the ferromagnetic or paramagnetic
material therein. In one embodiment, the second layer is an inner
layer, to minimize any microbiological or other effects of the
ferromagnetic or paramagnetic material on the patient.
[0010] The balloon may be detectable when viewed by magnetic
resonance imaging as a dark image or alternatively as a bright
image, depending on the nature of the MRI visible material forming
the balloon. In a presently preferred embodiment, the MRI visible
layer extends the entire length of the balloon. However, the
ferromagnetic or paramagnetic material may be present in sections
of the balloon covering less than the entire area of the balloon,
including sections spaced apart along the length or around the
circumference of the balloon.
[0011] In a presently preferred embodiment, the MRI visible medical
device or component thereof is configured to be expandable or
inflatable. It is particularly important to avoid disadvantageous
effects on the strength of expandable or inflatable members, such
as catheter balloons and vascular grafts, because the members are
required to not tear or burst during expansion thereof. Thus, the
relatively low loading of ferromagnetic or paramagnetic material,
in accordance with the invention, is particularly advantageous in
expandable or inflatable members.
[0012] The medical device or component thereof may comprise a
variety of devices, including a vascular graft, a stent cover, and
an intravascular catheter component, for a variety of clinical
applications including coronary, peripheral, and neurological
applications. Stent covers and vascular grafts of the invention
generally comprise a tubular body formed at least in part of
polymeric material and the ferromagnetic or paramagnetic material.
The terminology vascular graft as used herein should be understood
to include grafts and endoluminal prostheses which are surgically
attached to vessels in procedures such as vascular bypass or
anastomosis, or which are implanted within vessels, as for example
in aneurysm repair or at the site of a balloon angioplasty or stent
deployment. A balloon catheter of the invention, such as an
angioplasty dilatation catheter or a stent delivery catheter,
generally comprises an elongated shaft with at least one lumen and
balloon on a distal shaft section with an interior in fluid
communication with the at least one lumen. A wall of the catheter
balloon, or a separate sheath member on an outer surface of the
balloon, may be MRI visible in accordance with the invention.
[0013] The balloon, or other medical device or component thereof,
of the invention has improved MRI visibility due to the
ferromagnetic or paramagnetic material, without a disadvantageous
effect on strength or compliance of the balloon. Additionally,
radiopaque marker bands are not required on the balloon catheter of
the invention for visualization of the balloon location in the
patient. As a result, the distal section of the balloon catheter is
more flexible and has a smaller profile for improved tracking
compared to conventional balloon catheters. These and other
advantages of the invention will become more apparent from the
following detailed description when taken in conjunction with the
accompanying exemplary drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is an elevational view, partially in section, of a
stent delivery balloon catheter having a covered stent on the
catheter balloon, which embodies features of the invention.
[0015] FIG. 2 is a transverse cross-section of the catheter shown
in FIG. 1 taken at line 2-2.
[0016] FIG. 3 is a transverse cross-section of the catheter shown
in FIG. 1 taken at line 3-3, showing the covered stent disposed
over the inflatable balloon.
[0017] FIG. 4 is an elevational view, partially in section, of a
vascular graft or stent cover which embodies features of the
invention.
[0018] FIG. 5 is a transverse cross-section of the graft or cover
shown in FIG. 4, taken along lines 5-5.
DETAILED DESCRIPTION OF THE INVENTION
[0019] FIGS. 1-3 illustrate an over-the-wire type stent delivery
balloon catheter 10 embodying features of the invention. Catheter
10 generally comprises an elongated catheter shaft 12 having an
outer tubular member 14 and an inner tubular member 16. Inner
tubular member 16 defines a guidewire lumen 18 adapted to slidingly
receive a guidewire 20, and the coaxial relationship between outer
tubular member 14 and inner tubular member 16 defines annular
inflation lumen 22 (see FIGS. 2 and 3, illustrating transverse
cross sections of the catheter 10 of FIG. 1, taken along lines 2-2
and 3-3 respectively). An inflatable balloon 24 is disposed on a
distal section of catheter shaft 12. Balloon 24 has a proximal
shaft section sealingly secured to the distal end of outer tubular
member 14 and a distal shaft section sealingly secured to the
distal end of inner tubular member 16, so that its interior is in
fluid communication with inflation lumen 22. An adapter 26 at the
proximal end of catheter shaft 12 is configured to provide access
to guidewire lumen 18, and to direct inflation fluid through arm 28
into inflation lumen 22. Balloon 24 has an inflatable working
length located between tapered sections of the balloon. An
expandable stent 30 is mounted on the balloon working length, with
a stent cover 40 on an outer surface of the stent 30. FIG. 1
illustrates the balloon 24 in an uninflated configuration prior to
deployment of the stent 30. The distal end of the catheter may be
advanced in a conventional manner to a desired region of a
patient's vessel 32 defining a body lumen, and balloon 24 inflated
to expand stent 30, thereby implanting the stent in the body
lumen.
[0020] The balloon 24 is formed of a polymeric material and an
amount of ferromagnetic or paramagnetic material which is
sufficient to make the balloon MRI visible and insufficient to make
the balloon radiopaque within the patient. The ferromagnetic or
paramagnetic material is preferably dispersed in the polymeric
material forming the balloon wall, and in a presently preferred
embodiment, the dispersed material is a ferromagnetic material. In
the embodiment illustrated in FIG. 1, the balloon comprises an
outer layer 33 and an inner layer 34, at least one of which is
formed of the polymeric material/ferromagnetic or paramagnetic
dispersion. The outer and inner layers 33/34 may be formed of the
same polymeric material or different polymeric materials. A variety
of suitable polymeric materials may be used to form the balloon,
conventional in medical device balloon construction, including
polyamides such as nylon 11 or nylon 12, copolyamides such as
polyether block amide (PEBAX), copolyesters such as HYTREL or
ARNITEL.
[0021] In a presently preferred embodiment, the amount of
ferromagnetic or paramagnetic material is about 1% to about 30%,
preferably about 5% to about 20%, by weight of the polymeric
material/ferromagnetic or paramagnetic material dispersion,
depending on the magnetic field strength, gradient field strength,
and pulse sequences of the MRI system being used, as well as the
clinical application of the catheter. The preferred percentages are
for a multilayered balloon with a first layer formed of the MRI
visible material dispersed in a polymer (i.e., the MRI visible
layer), and a second layer free of the ferromagnetic or
paramagnetic material. In an alternative embodiment in which the
balloon is a single layered balloon (not shown) formed of the MRI
visible material dispersed in a polymer, the concentration of
ferromagnetic or paramagnetic material is typically lower, as for
example about 50% lower than the above values for a single layered
balloon having a wall thickness about 50% greater than the wall
thickness of the MRI visible layer of the multilayered balloon.
Applied as a coating, the ferromagnetic or paramagnetic material is
preferably about 10% to about 20% or more by weight of the
balloon.
[0022] The balloon 24 has a rupture pressure of about 200 to about
390 psi, preferably about 270 to about 330 psi. The rupture
pressure is preferably the same as the rupture pressure of a
balloon otherwise identical to the balloon but without the
ferromagnetic or paramagnetic material.
[0023] The balloon catheter 10 can be used, for example in a
balloon angioplasty procedure or stent deployment to treat a
stenosed region of the patient's vasculature. The catheter 10 is
introduced into the vessel 32 defining the body lumen, and advanced
therein. The balloon is visualized under MRI to position the
balloon at the desired location in the body lumen. The balloon is
then inflated by introduction of inflation fluid into the balloon
interior via the inflation lumen. A contrast solution is typically
introduced into the balloon which doubles as the inflation fluid,
and around the balloon through the guiding catheter, to enhance
visibility of the balloon. A presently preferred contrast solution
for a ferromagnetic containing balloon is a paramagnetic containing
contrast solution. Because the wall of the balloon can be
visualized during inflation thereof, the balloon 24 can be inflated
at the site of a lesion in the body lumen to determine information
about the lesion as part of a MRI diagnostic procedure.
Specifically, for example, the compliance of the lesion to the
inflated balloon can be determine by observing the balloon inflate
against the lesion. Following the procedure, the balloon is
deflated, and the catheter repositioned or removed from the
patient.
[0024] Co-extruded balloon tubing, formed of a 20 wt % dispersion
of iron oxide in a PEBAX 72D or Nylon 12 polymeric material as the
inner layer of the multilayered balloon with a PEBAX 72D outer
layer, was blow molded to form a balloon. The iron oxide particles
had a particle size of about 0.01 .mu.m. The balloon had a dual
wall thickness of about 40 .mu.m, and a burst pressure of about 250
psi to about 300 psi. The balloon was inflated at an inflation
pressure of about 116 psi to about 150 psi to an inflated diameter
of 3 mm, and MRI images of the inflated balloon were obtained at a
field strength of 1.5 Tesla. A 1% to 10% Gadolinium solution in
water is preferably used as a contrast solution within and/or
around the balloon to enhance the visibility of the iron oxide
containing balloon.
[0025] To the extent not discussed herein, the various catheter
components can be formed conventionally of materials commonly used
in catheter construction. The balloon 24 is typically secured to
the catheter shaft as is conventionally known by adhesive or fusion
bonding.
[0026] The dimensions of catheter 10 are determined largely by the
size of the guidewires to be employed and the size of the artery or
other body lumen through which the catheter must pass or the size
of the stent being delivered. The outer tubular member 14 typically
has an inner diameter of about 0.015 to about 0.035 inch (0.038 to
0.089 cm), usually about 0.03 inch (0.076 cm). The inner tubular
member 16 typically has an outer diameter of about 0.012 to about
0.016 inch (0.030 to 0.041 cm), usually about 0.014 inch (0.036
cm). The overall working length of the catheter 10 may range from
about 100 to about 150 cm, and is typically about 135 cm.
Preferably, balloon 24 has a length about 0.5 cm to about 6 cm and
typically about 2 cm, and an inflated working diameter of about 1
to about 8 mm, typically about 3 mm.
[0027] FIGS. 4 and 5 illustrate another embodiment of the
invention, in which the expandable MRI visible medical device is a
vascular graft 50. The vascular graft 50 generally comprises a
tubular body 51 formed at least in part of a polymeric material and
a ferromagnetic or paramagnetic material in accordance with the
invention, having a lumen 52 therein and ports 53, 54 at either end
of the graft 50. The graft 50 is configured for being implanted in
the patient, and it may be expanded into place within a vessel, or
surgically attached to a vessel such as to a free end or a side
wall of a vessel. The graft 50 length is generally about 4 to about
80 mm, and more specifically about 10 to about 50 mm, depending on
the application, and single wall thickness is typically about 40
.mu.m to about 2000 .mu.m, preferably about 100 .mu.m to about 1000
.mu.m. The diameter is generally about 1 to about 35 mm, preferably
about 3 to about 12 mm, depending on the application. Stent cover
40 is similar to vascular graft 50, except it is on a stent as
illustrated in FIG. 1.
[0028] While the present invention is described herein in terms of
certain preferred embodiments, those skilled in the art will
recognize that various modifications and improvements may be made
to the invention without departing from the scope thereof. For
example, in the embodiment illustrated in FIG. 1, the catheter is
over-the-wire stent delivery catheter. However, one of skill in the
art will readily recognize that other types of intravascular
catheters may be used, such as rapid exchange balloon catheters
having a distal guidewire port and a proximal guidewire port and a
short guidewire lumen extending between the proximal and distal
guidewire ports in a distal section of the catheter. Additionally,
although the balloon catheter illustrated in FIG. 1 is a stent
deploying catheter, a variety of balloon catheters may be used
including dilatation balloon catheters. Moreover, although
individual features of one embodiment of the invention may be
discussed herein or shown in the drawings of the one embodiment and
not in other embodiments, it should be apparent that individual
features of one embodiment may be combined with one or more
features of another embodiment or features from a plurality of
embodiments.
* * * * *