U.S. patent application number 12/126631 was filed with the patent office on 2008-09-11 for small vessel ultrasound cathter.
Invention is credited to Tim Abrahamson, Wm. Gerrit Barrere, Frederick J. Bennett, Curtis Genstler, George Keilman, Oscar E. Rodriguez, Perry Todd Thompson, Richard R. Wilson.
Application Number | 20080221506 12/126631 |
Document ID | / |
Family ID | 27541141 |
Filed Date | 2008-09-11 |
United States Patent
Application |
20080221506 |
Kind Code |
A1 |
Rodriguez; Oscar E. ; et
al. |
September 11, 2008 |
SMALL VESSEL ULTRASOUND CATHTER
Abstract
An ultrasound catheter adapted for accessing small vessels in
the distal anatomy is disclosed. The ultrasound catheter comprises
an elongate tubular body formed with a delivery lumen. The
flexibility and dimensions of the tubular body allow access to the
distal anatomy by advancement over the guidewire. An ultrasound
radiating member is provided along the distal end portion of the
tubular body for emitting ultrasound energy at a treatment site. A
drug solution may also be delivered through the delivery lumen and
out an exit port to the treatment site.
Inventors: |
Rodriguez; Oscar E.;
(Pembroke Pines, FL) ; Genstler; Curtis;
(Snohomoish, WA) ; Abrahamson; Tim; (Seattle,
WA) ; Barrere; Wm. Gerrit; (Lake Forest Park, WA)
; Bennett; Frederick J.; (Bellevue, WA) ; Keilman;
George; (Woodinville, WA) ; Wilson; Richard R.;
(Seattle, WA) ; Thompson; Perry Todd; (Kirkland,
WA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
27541141 |
Appl. No.: |
12/126631 |
Filed: |
May 23, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10309417 |
Dec 3, 2002 |
7384407 |
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12126631 |
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60336660 |
Dec 3, 2001 |
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60336627 |
Dec 3, 2001 |
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60336571 |
Dec 3, 2001 |
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60336630 |
Dec 3, 2001 |
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60344422 |
Dec 28, 2001 |
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Current U.S.
Class: |
604/22 |
Current CPC
Class: |
A61N 7/00 20130101; A61M
2025/0034 20130101; A61B 17/2202 20130101; A61N 2007/0078 20130101;
A61M 2025/0039 20130101 |
Class at
Publication: |
604/22 |
International
Class: |
A61B 17/22 20060101
A61B017/22 |
Claims
1. A method of treating a small vessel, comprising: providing a
first guidewire, an elongate outer sheath, and a second guidewire
having an ultrasound radiating member disposed along a distal end;
advancing said first guidewire though a patient's vasculature to a
treatment site; advancing said elongate outer sheath over said
first guidewire to said treatment site; removing said first
guidewire from said vasculature; advancing said second guidewire
through a delivery lumen of said elongate outer sheath such that
said ultrasound radiating member is located along a distal end
portion of said elongate outer sheath; and emitting ultrasound
energy from said ultrasound radiating member to said treatment
site.
2. The method of claim 2, further comprising delivering a drug
solution through said delivery lumen to said treatment site.
3. A method of treating an occlusion at a treatment site within a
patient's vasculature comprising: providing a guidewire having a
proximal region and a distal region opposite the proximal region,
wherein an ultrasound radiating member is mounted in the guidewire
distal region; positioning the guidewire within the patient's
vasculature, such that the ultrasound radiating member is adjacent
to the treatment site; advancing an elongate tubular body over a
portion of the guidewire such that the ultrasound radiating member
is not covered by the elongate tubular body, the elongate tubular
body having an inner diameter greater than an outer diameter of the
guidewire; passing a therapeutic compound through an annulus formed
between the elongate tubular body and the guidewire; and emitting
ultrasonic energy from the ultrasound radiating member.
4. The method of claim 3, wherein the guidewire comprises a hollow,
cylindrical hypotube.
5. The method of claim 3, wherein a plurality of electrical
conductors are passed through the guidewire.
6. The method of claim 3, further comprising sensing a temperature
at the treatment site.
7. The method of claim 3, further comprising moving the guidewire
simultaneously with the emission of ultrasonic energy from the
ultrasound radiating member.
8. The method of claim 3, further comprising imparting a shape to
the elongate tubular body before advancing the elongate tubular
body over the guidewire, the shape configured to facilitate the
advancement of the elongate tubular body over the guidewire.
Description
RELATED APPLICATIONS
[0001] The present application is a divisional application of U.S.
application Ser. No. 10/309,417, filed Dec. 3, 2002, which claims
priority to U.S. Provisional Application No. 60/336,660, filed Dec.
3, 2001, U.S. Provisional Application No. 60/336,627, filed Dec. 3,
2001, U.S. Provisional Application No. 60/336,571, filed Dec. 3,
2001, U.S. Provisional Application No. 60/336,630, filed Dec. 3,
2001 and U.S. Provisional Application No. 60/344,422, filed Dec.
28, 2001, each of which is hereby incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to a catheter having an
ultrasound assembly useful for delivering ultrasound energy at a
treatment site in a body. The apparatus is particularly well suited
for delivering ultrasound energy at a treatment site located within
a small blood vessel in the distal anatomy.
DESCRIPTION OF THE RELATED ART
[0003] Several therapeutic and diagnostic applications use
ultrasound energy. For example, ultrasound energy can be used to
enhance the delivery and therapeutic effect of various therapeutic
compounds. See e.g., U.S. Pat. Nos. 4,821,740, 4,953,565 and
5,007,438. In some applications, it is desirable to use an
ultrasound catheter to deliver the ultrasound energy and/or
therapeutic compound to a specific treatment site in the body. Such
an ultrasound catheter typically comprises an elongate member
configured for advancement through a patient's vasculature. An
ultrasound assembly is mounted along the distal end portion of the
elongate member and is adapted for emitting ultrasound energy. The
ultrasound catheter may include a delivery lumen for delivering the
therapeutic compound to the treatment site. In this manner, the
ultrasound energy can be emitted at the treatment site to enhance
the desired therapeutic effects and/or delivery of the therapeutic
compound.
[0004] In one particular application, ultrasound catheters have
been successfully used to treat human blood vessels that have
become occluded by plaque, thrombi, emboli or other substances that
reduce the blood carrying capacity of the vessel. See e.g., U.S.
Pat. No. 6,001,069. To remove the blockage, the ultrasound catheter
is advanced through the patient's vasculature to deliver solutions
containing dissolution compounds directly to the blockage site. To
enhance the therapeutic effects of the dissolution compound,
ultrasound energy is emitted into the compound and/or the
surrounding tissue.
[0005] In another application, ultrasound catheters may be used to
perform gene therapy on an isolated region of a blood vessel or
other body lumen. For example, as disclosed in U.S. Pat. No.
6,135,976 an ultrasound catheter can be provided with one or more
expandable members for occluding a section of the body lumen at a
treatment site. A gene therapy composition is delivered to the
treatment site through the delivery lumen of the catheter. The
ultrasound assembly is used to emit ultrasound energy at the
treatment site to enhance the entry of the gene composition into
the cells in the body lumen.
[0006] In addition to the applications discussed above, ultrasound
catheters may be used for a wide variety of other purposes, such
as, for example, delivering and activating light activated drugs
with ultrasound energy (see e.g., U.S. Pat. No. 6,176,842).
[0007] Over the years, numerous types of ultrasound catheters have
been proposed for various therapeutic purposes. However, none of
the existing ultrasound catheters is well adapted for effective use
within small blood vessels in the distal anatomy. For example, in
one primary shortcoming, the region of the catheter on which the
ultrasound assembly is located (typically along the distal end
portion) is relatively rigid and therefore lacks the flexibility
necessary for navigation through difficult regions of the distal
anatomy. Furthermore, it has been found that it is very difficult
to manufacture an ultrasound catheter having a sufficiently small
diameter for use in small vessels while providing adequate
pushability and torqueability. Still further, it has been found
that the distal tip of an ultrasound catheter can easily damage the
fragile vessels of the distal anatomy during advancement through
the patient's vasculature.
[0008] Accordingly, an urgent need exists for an improved
ultrasound catheter that is capable of safely and effectively
navigating small blood vessels. It is also desirable that such a
device be capable of delivering adequate ultrasound energy to
achieve the desired therapeutic purpose. It is also desirable that
such a device be capable of accessing a treatment site in fragile
distal vessels in a manner that is safe for the patient and that is
not unduly cumbersome. The present invention addresses these
needs.
SUMMARY OF THE INVENTION
[0009] There is provided in accordance with one aspect of the
present invention, an apparatus adapted for delivering ultrasound
energy within small blood vessels. The apparatus comprises an
elongate outer sheath having dimensions that allow access to the
distal anatomy, including but not limited to neurovascular and
other small vessels. An elongate inner core extends through a
central lumen along the entire length of the catheter and
terminates at an exit port. The inner core is provided with a
delivery lumen sized for advancement over the guidewire. The
delivery lumen may also be used to deliver a drug solution through
the exit port to a treatment site. An ultrasound radiating member
is provided along the distal end portion of the inner core at a
location distal to the outer sheath. A sleeve may be provided over
the ultrasound radiating member.
[0010] In one aspect, a flexible joint is provided at a location
proximal to the ultrasound radiating member to facilitate
advancement of the catheter through a patient's vasculature. In one
embodiment, the flexible joint is formed by configuring the inner
core with a corrugated region having a reduced bending resistance.
In another embodiment, the flexible joint is provided by a braided
portion that is used to connect the outer sheath with the
sleeve.
[0011] In another aspect, a soft tip assembly is provided for
reducing trauma or damage to tissue along the inner wall of a blood
vessel. The soft tip assembly may be attached to the distal end of
the catheter using a sleeve. The soft tip assembly preferably has a
rounded tip.
[0012] In another aspect, the catheter is provided with a shapeable
wire along the distal end portion for pre-shaping the distal end
portion of the catheter. Pre-shaping the distal end portion
facilitates advancement over curves in the guidewire. The shapeable
wire may be tapered.
[0013] In another aspect, a stiffening member is provided along the
exit port at the distal tip of the catheter. The stiffening member
reduces the likelihood of "fish-mouthing" and may be used in
cooperation with the guidewire to provide a flow control valve.
[0014] In another aspect, an ultrasound radiating member is
attached to or mounted on the guidewire. The guidewire is slidably
received by a delivery lumen in an outer sheath for advancement of
the ultrasound radiating member to a desired treatment site. In
this embodiment, the positions of the outer sheath and the
ultrasound radiating member are independently adjustable.
[0015] In yet another aspect, an elongate tubular body is provided
with an exterior surface, wherein a distal end portion of the
tubular body has an outer diameter of less than about 5 French for
advancement through a small blood vessel. The tubular body defines
a delivery lumen extending longitudinally therethrough and
terminates at an exit port at a distal tip. A hypotube is
configured to be slidably received within the delivery lumen and an
ultrasound radiating member is coupled to a distal end portion of
the hypotube. The hypotube is advanceable through the delivery
lumen in the tubular body and out through the exit port for
placement of the ultrasound radiating member at a treatment site. A
pair of wires extends longitudinally through an inner lumen in the
hypotube for providing an electrical signal to the ultrasound
radiating member.
[0016] In yet another aspect, a method of treating a small blood
vessel is provided. The method generally includes providing a first
guidewire, an elongate tubular body, and a second guidewire having
an ultrasound radiating member disposed along a distal end. The
first guidewire is advanced through the patient's vasculature to a
treatment site. The elongate tubular body (e.g., an outer sheath)
is advanced over the first guidewire to the treatment site. The
first guidewire is removed from the patient's vasculature. The
second guidewire is advanced through a lumen of the elongate
tubular body such that the ultrasound radiating member is located
within a distal end portion of the elongate tubular body and
ultrasound energy is emitted from the ultrasound radiating member
at the treatment site.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a side view of an ultrasound catheter that is
particularly well suited for insertion into small blood vessels of
the human body.
[0018] FIG. 2A is a cross-sectional view of a distal end of the
ultrasound catheter of FIG. 1.
[0019] FIG. 2B is a cross-sectional view of the ultrasound catheter
taken through line 2B-2B of FIG. 2A.
[0020] FIG. 3 is an alternative embodiment of the ultrasound
catheter including a stiffener at the distal tip.
[0021] FIG. 4 is a cross-sectional view of the distal end of an
ultrasound catheter wherein a portion of the inner core has a
corrugated configuration for enhanced flexibility.
[0022] FIG. 5 is a cross-sectional view of the distal end of an
ultrasound catheter wherein the proximal joint comprises braided
sections for enhanced flexibility.
[0023] FIG. 6A is a cross-sectional view of the distal end of an
ultrasound catheter including a bendable wire adapted for providing
a shapeable tip.
[0024] FIG. 6B is a cross-sectional view of the embodiment of FIG.
6A with the shapeable tip pre-formed to facilitate advancement over
a guidewire.
[0025] FIG. 7A is a top view of the distal end of an ultrasound
catheter having a soft tip assembly.
[0026] FIG. 7B is a cross-sectional view of the soft tip assembly
taken through line 7B-7B of FIG. 7A.
[0027] FIG. 8 is a side view an ultrasound element attached to the
distal end of a guidewire.
[0028] FIG. 9 is a cross-sectional view of an ultrasound catheter
used with the ultrasound element and guidewire of FIG. 8.
[0029] FIG. 10 is a cross-sectional view of a distal end of another
modified embodiment of an ultrasound catheter that can be used with
the ultrasound element and guidewire of FIG. 8.
[0030] FIG. 11 is a side view of a distal end of a treatment wire
wherein an ultrasound element is provided along the distal end of a
hypotube.
[0031] FIG. 12 is a side view of a distal end of an ultrasound
catheter that incorporates the treatment wire of FIG. 11.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] The advancement of an ultrasound catheter through a blood
vessel to a treatment site can be difficult and dangerous,
particularly when the treatment site is located within a small
vessel in the distal region of a patient's vasculature. To reach
the treatment site, it is often necessary to navigate a tortuous
path around difficult bends and turns. During advancement through
the vasculature, bending resistance along the distal end portion of
the catheter can severely limit the ability of the catheter to make
the necessary turns. Moreover, as the catheter is advanced, the
distal tip of the catheter is often in contact with the inner wall
of the blood vessel. The stiffness and rigidity of the distal tip
of the catheter may lead to significant trauma or damage to the
tissue along the inner wall of the blood vessel. As a result,
advancement of an ultrasound catheter through small blood vessels
can be extremely hazardous. Therefore, a need exists for an
improved ultrasound catheter design that allows a physician to more
easily navigate difficult turns in small blood vessels while
minimizing trauma and/or damage along the inner walls of the blood
vessels.
[0033] To address this need, preferred embodiments of the present
invention described herein provide an ultrasound catheter that is
well suited for use in the treatment of small blood vessels or
other body lumens having a small inner diameter. The ultrasound
catheter can be used to enhance the therapeutic effects of drugs,
medication and other pharmacological agents at a treatment site
within the body. See e.g., U.S. Pat. Nos. 5,318,014, 5,362,309,
5,474,531, 5,628,728, 6,001,069, and 6,210,356. Certain preferred
embodiments of the ultrasound catheter are particularly well suited
for use in the treatment of thrombotic occlusions in small blood
vessels, such as, for example, the cerebral arteries. In addition,
preferred embodiments may also find utility in other therapeutic
applications, such as, for example, performing gene therapy (see
e.g., U.S. Pat. No. 6,135,976), activating light activated drugs
for producing targeted tissue death (see e.g., U.S. Pat. No.
6,176,842) and causing cavitation to produce various desirable
biological effects (see e.g., U.S. Pat. No. RE36,939). Moreover,
such therapeutic applications may be used in wide variety of
locations within the body, such as, for example, in other parts of
the circulatory system, solid tissues, duct systems and body
cavities. It is also anticipated that the ultrasound catheters
disclosed herein, and variations thereof, may find utility in other
medical applications, such as, for example, diagnostic and imaging
applications.
[0034] Ultrasound catheters and methods disclosed herein, and
similar variations thereof, may also be useful for applications
wherein the ultrasound energy provides a therapeutic effect by
itself. For example, ultrasound energy may be effective for uses
such as preventing and/or reducing stenosis and/or restenosis,
tissue ablation, abrasion or disruption, promoting temporary or
permanent physiological changes in intracellular or intercellular
structures, or rupturing micro-balloons or micro-bubbles for drug
delivery. See e.g., U.S. Pat. Nos. 5,269,291 and 5,431,663. In
addition, the methods and devices disclosed herein may also find
utility in applications that do not require the use of a catheter.
For example the methods and devices may be used for enhancing
hyperthermic drug treatment or using an external ultrasound source
to enhance the therapeutic effects of drugs, medication and other
pharmacological agents at a specific site within the body or to
provide a therapuetic or diagnostic effect by itself. See e.g.,
U.S. Pat. Nos. 4,821,740, 4,953,565, 5,007,438 and 6,096,000. The
entire disclosure of each of the above-mentioned patents is hereby
incorporated by reference herein and made a part of this
specification.
[0035] As used herein, the term "ultrasound energy" is a broad term
and is used in its ordinary sense and means, without limitation,
mechanical energy transferred through pressure or compression waves
with a frequency greater than about 20 KHz. In one embodiment, the
waves of the ultrasound energy have a frequency between about 500
KHz and 20 MHz and in another embodiment between about 1 MHz and 3
MHz. In yet another embodiment, the waves of the ultrasound energy
have a frequency of about 3 MHz.
[0036] As used herein, the term "catheter" is a broad term and is
used in its ordinary sense and means, without limitation, an
elongate flexible tube configured to be inserted into the body of a
patient, such as, for example, a body cavity, duct or vessel.
Preferred Features of Ultrasound Catheter
[0037] Referring now to FIGS. 1 through 2B, for purposes of
illustration, preferred embodiments of the present invention
provide an ultrasound catheter 100 that is particularly well suited
for use within small vessels of the distal anatomy, such as, for
example, in the remote, small diameter, neurovasculature in the
brain.
[0038] As shown in FIGS. 1 and 2A, the ultrasound catheter 100
generally comprises a multi-component tubular body 102 having a
proximal end 104 and a distal end 106. The tubular body 102 and
other components of the catheter 100 can be manufactured in
accordance with any of a variety of techniques well know in the
catheter manufacturing field. As discussed in more detail below,
suitable material dimensions can be readily selected taking into
account the natural and anatomical dimensions of the treatment site
and of the desired percutaneous access site.
[0039] Preferably, the tubular body 102 can be divided into at
least three sections of varying stiffness. The first section, which
preferably includes the proximal end 104, is generally more stiff
than a second section, which lies between the proximal end 104 and
the distal end 106 of the catheter. This arrangement facilitates
the movement and placement of the catheter 102 within small
vessels. The third section, which includes ultrasound radiating
element 124, is generally stiffer than the second section due to
the presence of the ultrasound radiating element 124.
[0040] In each of the embodiments described herein, the assembled
ultrasound catheter preferably has sufficient structural integrity,
or "pushability," to permit the catheter to be advanced through a
patient's vasculature to a treatment site without buckling or
kinking. In addition, the catheter has the ability to transmit
torque, such that the distal portion can be rotated into a desired
orientation after insertion into a patient by applying torque to
the proximal end.
[0041] The elongate flexible tubular body 102 comprises an outer
sheath 108 (see FIG. 2A) that is positioned upon an inner core 110.
In an embodiment particularly well suited for small vessels, the
outer sheath 108 comprises extruded PEBAX, PTFE, PEEK, PE,
polymides, braided polymides and/or other similar materials. The
distal end portion of the outer sheath 108 is adapted for
advancement through vessels having a very small diameter, such as
those in the neurovasculature of the brain. Preferably, the distal
end portion of the outer sheath 108 has an outer diameter between
about 2 and 5 French. More preferably, the distal end portion of
the outer sheath 108 has an outer diameter of about 2.8 French. In
one preferred embodiment, the outer sheath 108 has an axial length
of approximately 150 centimeters.
[0042] In other embodiments, the outer sheath 108 can be formed
from a braided tubing formed of, by way of example, high or low
density polyethylenes, urethanes, nylons, etc. Such an embodiment
enhances the flexibility of the tubular body 102. For enhanced
pushability and torqueability, the outer sheath 108 may be formed
with a variable stiffness from the proximal to the distal end. To
achieve this, a stiffening member may be included along the
proximal end of the tubular body 102.
[0043] The inner core 110 defines, at least in part, a delivery
lumen 112, which preferably extends longitudinally along the entire
length of the catheter 100. The delivery lumen 112 has a distal
exit port 114 and a proximal axis port 116. Referring again to FIG.
1, the proximal access port 116 is defined by drug inlet port 117
of a back end hub 118, which is attached to the proximal end 104 of
the other sheath 108. The illustrated back end hub 118 is
preferably attached to a control box connector 120, the utility of
which will be described in more detail below.
[0044] The delivery lumen 112 is preferably configured to receive a
guide wire (not shown). Preferably, the guidewire has a diameter of
approximately 0.008 to 0.012 inches. More preferably, the guidewire
has a diameter of about 0.010 inches. The inner core 110 is
preferably formed from polymide or a similar material which, in
some embodiments, can be braided to increase the flexibility of the
tubular body 102.
[0045] With particular reference to FIGS. 2A and 2B, the distal end
106 of the catheter 102 preferably includes the ultrasound
radiating element 124. In the illustrated embodiment, the
ultrasound radiating element 124 comprises an ultrasound
transducer, which converts, for example, electrical energy into
ultrasound energy. In a modified embodiment, the ultrasound energy
can be generated by an ultrasound transducer that is remote from
the ultrasound radiating element 124 and the ultrasound energy can
be transmitted via, for example, a wire to the ultrasound radiating
element 124.
[0046] In the embodiment illustrated in FIGS. 2A and 2B, the
ultrasound radiating element 124 is configured as a hollow
cylinder. As such, the inner core 110 can extend through the lumen
of the ultrasound radiating element 124. The ultrasound radiating
element 124 can be secured to the inner core 110 in any suitable
manner, such as with an adhesive. A potting material may also be
used to further secure the mounting of the ultrasound radiating
element along the central core.
[0047] In other embodiments, the ultrasound radiating element 124
can be configured with a different shape without departing from the
scope of the invention. For example, the ultrasound radiating
element may take the form of a solid rod, a disk, a solid rectangle
or a thin block. Still further, the ultrasound radiating element
124 may comprise a plurality of smaller ultrasound radiating
elements. The illustrated arrangement is the generally preferred
configuration because it provides for enhanced cooling of the
ultrasound radiating element 124. For example, in one preferred
embodiment, a drug solution can be delivered through the delivery
lumen 112. As the drug solution passes through the lumen of the
ultrasound radiating element, the drug solution may advantageously
provide a heat sink for removing excess heat generated by the
ultrasound radiating element 124. In another embodiment, a return
path can be formed in the space 138 between the outer sheath and
the inner core such that coolant from a coolant system can be
directed through the space 138.
[0048] The ultrasound radiating element 40 is preferably selected
to produce ultrasound energy in a frequency range that is well
suited for the particular application. Suitable frequencies of
ultrasound energy for the applications described herein include,
but are not limited to, from about 20 KHz to about 20 MHz. In one
embodiment, the frequency is between about 500 KHz and 20 MHz and
in another embodiment from about 1 MHz and about 3 MHz. In yet
another embodiment, the ultrasound energy has a frequency of about
3 MHz.
[0049] As mentioned above, in the illustrated embodiment,
ultrasound energy is generated from electrical power supplied to
the ultrasound radiating element 124. The electrical power can be
supplied through the controller box connector 120, which is
connected to a pair wires 126, 128 that extend through the catheter
body 102. The electrical wires 126, 128 can be secured to the inner
core 110, lay along the inner core 110 and/or extend freely in the
space between the inner core 110 and the outer sheath 108. In the
illustrated arrangement, the first wire 126 is connected to the
hollow center of the ultrasound radiating element 124 while the
second wire 128 is connected to the outer periphery of the
ultrasound radiating element 124. The ultrasound radiating element
124 is preferably, but is not limited to, a transducer formed of a
piezolectic ceramic oscillator or a similar material.
[0050] With continued reference to FIGS. 2A and 2B, the distal end
104 of the catheter 100 preferably includes a sleeve 130, which is
generally positioned about the ultrasound radiating element 124.
The sleeve 130 is preferably constructed from a material that
readily transmits ultrasound energy. Suitable materials for the
sleeve 130 include, but are not limited to, polyolefins,
polyimides, polyester and other materials having a relatively low
impedance to ultrasound energy. Low ultrasound impedance materials
are materials that readily transmit ultrasound energy with minimal
absorption of the ultrasound energy. The proximal end of the sleeve
130 can be attached to the outer sheath 108 with an adhesive 132.
To improve the bonding of the adhesive 132 to the outer sheath 108,
a shoulder 127 or notch may be formed in the outer sheath for
attachment of the adhesive thereto. Preferably, the outer sheath
108 and the sleeve 130 have substantially the same outer
diameter.
[0051] In a similar manner, the distal end of the sleeve 130 can be
attached to a tip 134. In the illustrated arrangement, the tip 134
is also attached to the distal end of the inner core 110.
Preferably, the tip is between about 0.5 and 4.0 millimeters in
length. More preferably, the tip is about 2.0 millimeters in
length. As illustrated, the tip is preferably rounded in shape to
reduce trauma or damage to tissue along the inner wall of a blood
vessel or other body structure during advancement toward a
treatment site.
[0052] With continued reference to FIG. 2B, the catheter 100
preferably includes at least one temperature sensor 136 along the
distal end 106. The temperature sensor 136 is preferably located on
or near the ultrasound radiating element 124. Suitable temperature
sensors include but are not limited to, diodes, thermistors,
thermocouples, resistance temperature detectors (RTDs), and fiber
optic temperature sensors that used thermalchromic liquid crystals.
The temperature sensor is preferably operatively connected to a
control box (not shown) through a control wire, which extends
through the catheter body 102 and back end hub 118 and is
operatively connected to a control box through the control box
connector 120. The control box preferably includes a feedback
control system having the ability to monitor and control the power,
voltage, current and phase supplied to the ultrasound radiating
element. In this manner, the temperature along the relevant region
of the catheter can be monitored and controlled for optimal
performance. Details of the control box can be found in Assignee's
co-pending provisional application entitled CONTROL POD FOR
ULTRASONIC CATHETER, Application Ser. No. 60/336,630, filed Dec. 3,
2001, which is incorporated by reference in its entirety.
[0053] In one exemplary application of the ultrasound catheter 100
described above, the apparatus may be used to remove a thrombotic
occlusion from a small blood vessel. In one preferred method of
use, a free end of a guidewire is percutaneously inserted into the
patient's vasculature at a suitable first puncture site. The
guidewire is advanced through the vasculature toward a treatment
site wherein the blood vessel is occluded by the thrombus. The
guidewire wire is preferably then directed through the
thrombus.
[0054] After advancing the guidewire to the treatment site, the
catheter 100 is thereafter percutaneously inserted into the
vasculature through the first puncture site and is advanced along
the guidewire towards the treatment site using traditional
over-the-guidewire techniques. The catheter 100 is advanced until
the distal end 106 of the catheter 100 is positioned at or within
the occlusion. The distal end 106 of the catheter 100 may include
one or more radiopaque markers (not shown) to aid in positioning
the distal end 106 within the treatment site.
[0055] After placing the catheter, the guidewire can then be
withdrawn from the delivery lumen 112. A drug solution source (not
shown), such as a syringe with a Luer fitting, is attached to the
drug inlet port 117 and the controller box connector 120 is
connected to the control box. As such, the drug solution can be
delivered through the delivery lumen 112 and out the distal access
port 114 to the thrombus. Suitable drug solutions for treating a
thrombus include, but are not limited to, an aqueous solution
containing Heparin, Uronkinase, Streptokinase, and/or tissue
Plasminogen Activator (TPA).
[0056] The ultrasound radiating element 124 is activated to emit
ultrasound energy from the distal end 106 of the catheter 100. As
mentioned above, suitable frequencies for the ultrasound radiating
element 124 include, but are not limited to, from about 20 KHz to
about 20 MHz. In one embodiment, the frequency is between about 500
KHz and 20 MHz and in another embodiment between about 1 MHz and 3
MHz. In yet another embodiment, the ultrasound energy is emitted at
a frequency of about 3 MHz. The drug solution and ultrasound energy
are applied until the thrombus is partially or entirely dissolved.
Once the thrombus has been dissolved to the desired degree, the
catheter 100 is withdrawn from the treatment site.
Stiffening Component
[0057] Referring again to FIG. 2A, because the diameter of the
distal exit port 114 is often relatively large compared with the
diameter of the guidewire (not shown), a gap may exist between the
inner rim of the tip 134 and the guidewire. If sufficiently large,
this gap may cause the tip 134 of the catheter to catch or snag on
an object along the exit port 114. If the tip 134 catches on an
object, the exit port 114 may stretch (i.e., increase in diameter)
as the catheter is pushed forward. This effect is particularly
likely to occur at vessel bifurcations and will hereinafter be
referred to as "fish-mouthing."
[0058] FIG. 3 illustrates an embodiment adapted to reduce the
likelihood of fish-mouthing wherein a circular stiffening component
140 is provided along the distal tip 134. The circular stiffening
component 140 reduces the gap between the tip 134 and the
guidewire, and is preferably made of a stiff material, such as, for
example, aluminum, that will prevent the tip 134 from
fish-mouthing. Additionally, if the guidewire is formed with a
variable diameter, cooperation of the guidewire and the circular
stiffening component 140 may be advantageously used as a valve. By
adjusting the relative positions of the guidewire and catheter, it
is possible to control the delivery of drugs, medications, or other
therapeutic compounds through the exit port 114 along the tip 134.
As seen in FIG. 3, this embodiment also includes a variation of the
inner core 110A having a flared end that may be inserted into a
circumferential notch 142 formed in the distal tip 134. Insertion
of the flared end into the circumferential notch provides for
enhanced structural integrity.
[0059] In alternative embodiments, fish-mouthing may be prevented
by increasing the thickness of the tip 134, or by manufacturing the
tip 134 using a material with increased stiffness. In such
embodiments, the tip 134 will have decreased flexibility, and
therefore will be less susceptible to fish-mouthing.
Flexible Joint
[0060] Referring again to FIG. 2A, in modified embodiments of the
present invention, the rigidity of the catheter along the joint
(hereinafter referred to as the "proximal element joint") between
the outer sheath 108 and sleeve 130 may be reduced significantly.
The rigidity of the proximal element joint is reduced to further
enhance flexibility, prevent kinking of the flexible support
section of the catheter, and to facilitate tracking of the catheter
over the guidewire.
[0061] In such embodiments, the used of an adhesive may be
eliminated, and the proximal end of the sleeve 130 may be attached
to the outer sheath 108 at the proximal element joint using a
direct bonding method adapted to create a more flexible proximal
element joint. Examples of such direct bonding methods include, but
are not limited to, the use of heat, a solvent, a mold, or a cast.
Alternatively, a reflow, or "die wiping" technique may be employed
wherein an extruded catheter shaft is covered with a heat shrink
tube and heated to reflow and bond the polymers within the catheter
shaft. An external heat source may be employed in a reflow
technique, or if the catheter includes metal components at the
proximal element joint, radio frequency ("RF") energy may be used
to heat and bond the polymers within the catheter shaft.
[0062] FIG. 4 illustrates yet another alternative embodiment for
reducing the rigidity of the proximal element joint to thereby
enhance the flexibility of the ultrasound catheter. As illustrated
in FIG. 4, the inner core 410 includes a corrugated portion 452
along the proximal element joint just proximal of the ultrasound
radiating element 424. In such embodiments, a Teflon.RTM. liner 450
may be adapted to surround the inner surface of the corrugated
portion 452 of the inner core 410 to prevent the guidewire from
catching on the corrugations. Additionally, a flexible filler
material 456 and a flexible cover sleeve 454 may be adapted to
cover the exterior surface of the corrugated portion 452 of the
catheter to prevent the catheter from catching on the interior
walls of the vessel anatomy. A corrugated portion 452 of the inner
core 410 may be created by placing a close-fitting pin within a
portion of the polyimide material used to form the inner core, and
applying a compressive force to the polyimide material on either
side of the pin. When the pin is removed from the inner core 410,
the corrugated portion 452 of the inner core 410 will have enhanced
flexibility and will thereby increase the flexibility of the
ultrasound catheter.
[0063] In still other embodiments, the rigidity of the proximal
element joint may be further reduced by forming the inner core 410
of the delivery lumen 412 of a material with increased flexibility
and resistance to kinking. For example, the inner core 410 of the
delivery lumen 412 may comprise a Teflon.RTM.-lined polyimide
shaft. Additionally, a coil or braid may be incorporated into the
delivery lumen 412, thereby further reducing susceptibility to
kinking without increasing the rigidity of the catheter.
[0064] FIG. 5 illustrates yet another alternative embodiment
wherein the rigidity of the proximal element joint 548 is reduced
by providing a outer sheath 508 that includes an embedded braid
560. Furthermore, the outer sheath 508 is attached to the sleeve
530 using a flexible exposed braided portion 558. A flexible filler
material 556 and a flexible cover sleeve 554 are used to bond the
outer sheath 508, the sleeve 530 and the exposed braided portion
558 together. This embodiment provides the catheter with a flexible
region just proximal to the ultrasound radiating member 524. In
various preferred embodiments, the braided sections may be formed
of high or low density polyethylenes, urethanes or nylons.
Shapeable Tip
[0065] FIG. 6A illustrates yet another modified embodiment wherein
the ultrasound catheter provides improved tracking over the
guidewire 602. Prolapsing of a guidewire is most likely to occur at
small vessel radii, where the guidewire 602 follows a sharp turn,
and where the angle .theta. formed by the intersection between the
guidewire 602 and the catheter body is large. In order to reduce
the incident angle .theta. between the guidewire and catheter body,
a tapered wire 642 is provided along the exterior of the outer
sheath 608 for shaping the distal end of the catheter. The tapered
wire 642 may be set in a flexible potting or filler material 644,
which is contained within a flexible sleeve 646. The tapered wire
642 is preferably comprised of a pliable material, such that it may
be pre-formed into a selectable desired orientation before use.
Pre-forming of the tapered wire 642 assists the physician in
steering the catheter to follow the guidewire 602 reliably around
small vessel radii by reducing the angle .theta. formed by the
intersection between the guidewire 602 and the catheter body. The
tapered wire is preferably provided in the region surrounding the
ultrasound radiating element 624. FIG. 6B illustrates the
embodiment of FIG. 6A in use with the tip pre-formed for improved
tracking over the guidewire.
Soft Tip Assembly
[0066] In addition to having excellent flexibility, it is also
desirable for an ultrasound catheter to have a rounded and/or soft
tip assembly for minimizing trauma or damage to the tissue along
the inner wall of the blood vessel. This feature is particularly
important during advancement through small blood vessels in the
neurovasculature.
[0067] FIGS. 7A illustrates an alternative embodiment wherein the
distal end portion of an ultrasound catheter is provided with a
soft tip assembly 700. In the illustrated embodiment, the
ultrasound catheter generally comprises an elongate shaft body 702,
an ultrasound radiating element 704, an elongate soft tip 706 and a
connecting sleeve 708. The soft tip 706 of the catheter is
constructed to be softer and more flexible than the shaft body 702
for the purpose of minimizing or eliminating damage to the tissue
along the inner wall of a blood vessel. In the illustrated
embodiment, the soft tip 706 is configured as a substantially
hollow member including a delivery lumen 710. The lumen 710 may be
used for receiving a guidewire and/or for delivering drugs to a
treatment site. Preferably, the shaft body 702 and the soft tip 706
have substantially the same outer diameter. The delivery lumen 710
terminates at an exit port 720 at the extreme distal tip of the
soft tip assembly.
[0068] Still referring to FIG. 7A, the ultrasound radiating element
704 is provided at a location just distal to the shaft body 702 and
just proximal of the soft tip 710. Preferably, a small gap 712 is
provided between the ultrasound radiating element 704 and the
elongate body 702 and also between the ultrasound radiating element
704 and the soft tip 706. In the illustrated embodiment, a single
cylindrical ultrasound radiating element 704 is provided, however,
in alternative embodiments, others variations may be used, such as,
for example a plurality of smaller ultrasound radiating
elements.
[0069] In the illustrated embodiment, the shaft body 702,
ultrasound radiating element 704 and soft tip 706 are secured
together by the sleeve 708. The ultrasound radiating element 704 is
contained within the lumen of the sleeve 708. The proximal end 714
of the sleeve 708 extends over the distal portion of the shaft body
702. The distal end 716 of the sleeve 708 extends over the proximal
end of the soft tip 706. In one embodiment, the sleeve 708 is
formed of heat shrink tubing. To maximize effectiveness of the
ultrasound catheter, the sleeve 708 is preferably constructed of a
material having a low impedance to ultrasound energy. FIG. 7B
illustrates a cross-sectional view of the soft tip assembly of FIG.
7A as seen through line 7B-7B.
[0070] Referring again to FIG. 7A, the illustrated embodiment of
the soft tip assembly 706 is formed with a plurality of side holes
718. The side holes 718 are in communication with the delivery
lumen 710 and are provided for enhancing the delivery of drugs to
the treatment site. Using the side holes 718, the therapeutic agent
can be delivered radially at a location closer to the ultrasound
radiating element 704. The illustrated embodiment includes two side
holes, however, in alternative embodiments, any number of side
holes may be used without departing form the spirit and scope of
the invention. Alternatively, the soft tip assembly may be
configured without any side holes.
[0071] In alternative embodiments, the soft tip assembly may have a
solid tip wherein drugs exit the tip assembly only through side
ports. In the embodiments with a solid tip, the guidewire exits the
catheter through a side port, such as in a rapid exchange or
monorail catheter design. In another embodiment, the soft tip
assembly includes a radiopaque material to provide for high
visibility under fluoroscopy. In various alternative embodiments,
the soft tip assembly may have a variety of different lengths, such
as, for example, 1 mm, 3 mm and 6 mm.
[0072] In operation, the ultrasound catheter is advanced over a
guidewire that extends through the delivery lumen 710. As the
ultrasound catheter is advanced through a small blood vessel, the
soft tip assembly bends and conforms to the shape of the blood
vessel to reduce the pressure applied along the inner wall. The
rounded tip of the soft tip assembly also minimizes trauma to the
tissue as it is advanced along the inner walls of the blood
vessels. The soft tip assembly can bend to facilitate the
advancement of the catheter, yet will return to substantially its
original shape. After the ultrasound element is positioned in the
desired location, the guidewire may be removed and the delivery
lumen 710 used for the delivery of a therapeutic agent to the
treatment site.
[0073] The soft tip assembly is preferably made of a soft polymer
extrusion, such as, for example, polyimide. In one preferred method
of construction, the soft tip assembly is constructed by first
cutting the extruded soft tubular body into a length of
approximately 3 to 6 mm. The distal tip is then rounded and
smoothed using a heated die with the desired contour. In the
embodiments wherein side holes are provided, the side holes are
created using a 0.010 inch hole plunger. The soft tip assembly is
then attached to the elongate shaft body using an adhesive or by
thermal bonding. Alternatively, a length of heat shrink tubing may
be used to secure the shaft body to the soft tip assembly.
Ultrasound Element on a Guidewire
[0074] FIGS. 8 and 9 illustrate another modified embodiment of an
ultrasound catheter 850. As shown in FIG. 8, in this embodiment, an
ultrasound radiating element 852 is connected to or mounted on a
distal end 854 of a guidewire 856. In the illustrated arrangement,
the ultrasound radiating element 852 is in the shape of a hollow
cylinder. As such, the guidewire 856 can extend through the
ultrasound radiating element 852, which is positioned over the
guidewire 856. The ultrasound radiating element 852 can be secured
to the guidewire 856 in any suitable manner, such as with an
adhesive. In other embodiments, the ultrasound radiating element
856 can be of a different shape, such as, for example, a solid
cylinder, a disk, a solid rectangle or a plate attached to the
guidewire 856. The ultrasound radiating element 852 can also be
formed from a plurality of smaller ultrasound elements.
[0075] In the illustrated embodiment, ultrasound energy is
generated from electrical power supplied to the ultrasound
radiating element 852. As such, the ultrasound radiating element
852 is connected to a pair of wires 860, 862 that can extend
through the catheter body. In the illustrated embodiment, the wires
860, 862 are preferably secured to the guidewire 856 with the first
wire 860 is connected to the hollow center of the ultrasound
radiating element 852 and the second wire 862 connected to the
outer periphery of the ultrasound radiating element 852. As with
the previous embodiments, the ultrasound radiating element 852 is
preferably formed from, but is not limited to, a piezolectic
ceramic oscillator or a similar material. Other wiring schemes
include wires connected to both ends of a solid transducer or both
sides of a block. The ultrasound radiating element 852 and the
wires 860, 862 are preferably covered with a thin insulating
material 857.
[0076] FIG. 9 illustrates one embodiment of a catheter 850 that can
be used with the guidewire 856 described above. In this embodiment,
the catheter 850 includes an outer sheath 866, which defines the
delivery lumen 868. As such, the illustrated embodiment does not
include an inner core. The delivery lumen 868 includes a distal
opening 870. As will be explained below, in one arrangement, the
distal opening 870 can be configured such that the guidewire 856
and the ultrasound radiating element 852 can be withdrawn into the
catheter 850 through the distal opening 870. In such an
arrangement, a distal end 872 of the catheter 850 preferably
includes a sleeve 874, that is constructed from a material that
readily transmits ultrasound energy as described above. In another
arrangement, the distal opening 870 can be configured such that
ultrasound radiating element 852 can not be withdrawn into the
catheter 850 through the distal opening 870. In such an
arrangement, the ultrasound radiating element 852 is configured to
operate outside the catheter 850 near the distal opening 870.
[0077] In one embodiment, the distal end 854 of the guidewire 856
is percutaneously inserted into the arterial system at a suitable
first puncture site. The guidewire 856 and the ultrasound radiating
element 852 are advanced through the vessels towards a treatment
site, which includes a thrombotic occlusion. The guidewire 856 is
preferably then directed through the thrombotic occlusion.
[0078] The catheter 850 is thereafter percutaneously inserted into
the first puncture site and advanced along the guidewire 856
towards the treatment site using traditional over-the-guidewire
techniques. The catheter 850 is advanced until the distal end of
the catheter 856 is positioned at or within the occlusion.
Preferably, the distal end includes radio opaque markers to aid
positioning the distal end within the treatment site.
[0079] In one embodiment, the guidewire 856 can then be withdrawn
until the ultrasound radiating element 852 is positioned within the
distal end 874 of the catheter 850. In such an arrangement, the
catheter 850 can include a proximal stop 875 to aid the positioning
of the ultrasound radiating element 852. In another embodiment, the
guidewire can be withdrawn until the ultrasound radiating element
852 is located near or adjacent the distal opening 870. The
catheter 850 can then be operated as described above.
[0080] In another modified embodiment, a standard guidewire (not
shown) is percutaneously inserted into the first puncture site and
advanced through the vessels towards and preferably through the
occlusion. The catheter 850 is thereafter percutaneously inserted
into the first puncture site and advanced along the standard
guidewire towards the treatment site using traditional
over-the-guidewire techniques. The catheter 850 preferably is
advanced until the distal end of the catheter 850 is positioned at
or within the occlusion. The standard guidewire can then be
withdrawn from the delivery lumen. The guidewire 856 and ultrasound
radiating element 852 of FIG. 8 can then be inserted into the
delivery lumen. In one embodiment, the ultrasound radiating element
852 is advanced until it is positioned in the distal end of the
catheter 850. In another embodiment, the ultrasound radiating
element 852 is advanced until it exits the distal end 870 of the
delivery lumen 868. The catheter can then be operated as describe
above.
[0081] FIG. 10 illustrates yet another modified embodiment of an
ultrasound catheter 1000 that can be used with the guidewire 1056
and ultrasound radiating element 1052, as described above. In this
embodiment, the guidewire lumen 1068 is defined by an inner sleeve
or tube 1002. The distal end 1070 of the delivery lumen 1068 can be
configured as described above for preventing or withdrawing the
ultrasound radiating element 1052 into catheter 1050. In the
illustrated arrangement, the delivery lumen 1068 can be used to
transport the drug solution. In another arrangement, the space 1004
between the inner core 1002 and the outer sheath 1066 can be used
to transport the drug solution. In such an arrangement, the outer
sheath 1066 preferably includes one or more holes positioned at the
distal end 1072 of the outer sheath 1066. The catheter can be
advanced on the guidewire 856 of FIG. 8 or a standard guidewire as
described above.
Ultrasound Element on a Hyoptube
[0082] FIGS. 11 and 12 illustrate yet another embodiment of an
ultrasound catheter 1101 that is particularly well suited for use
with small vessels of the distal anatomy. As shown in FIG. 12, this
embodiment of the ultrasound catheter 1101 generally comprises a
treatment wire 1103 and a microcatheter 1105.
[0083] FIG. 11 illustrates a preferred embodiment of a treatment
wire 1103. As shown in FIG. 11, in this embodiment, an ultrasound
radiating element 1106 is connected to the distal tip of a hypotube
1108. As discussed with reference to the small vessel catheters
described above, the ultrasound radiating element can take many
shapes and forms. The ultrasound radiating element 1106 is potted
in an insulating material either as a conformal coating or potted
inside an outer sleeve. The potting 1110 over the ultrasound
radiating element 1106 sections is optimized for transmission of
ultrasound energy. In the embodiment illustrated in FIG. 11, the
width of the potted ultrasound radiating element 1112 is
approximately 0.018 inches. An epoxy or similar adhesive known in
the catheter manufacturing field connects the potted ultrasound
radiating element 1112 with the hypotube 1108 at junction 1114.
[0084] The hypotube 1108 is made from Nitinol or stainless steel or
other suitable material in accordance with the techniques and
materials known in the catheter manufacturing field. In one
embodiment, the hypotube has a diameter of approximately 0.014 to
0.015 inches. The hypotube 1108 provides an insulated lumen 1116
through which one can run power wires 1118 for the ultrasound
radiating element 1106 or wires for temperature sensors (not shown)
in the microcatheter 1105. The microcatheter 1105, into which the
treatment wire 1103 is inserted, has a diameter greater than the
width of the potted ultrasound radiating element 1112.
[0085] As shown in FIG. 11, in this embodiment, a flexible nose
1120 is connected to the distal end of the potted ultrasound
radiating element 1112. An epoxy or similar adhesive known in the
catheter manufacturing field connects the flexible nose 1120 to the
potted ultrasound radiating element 1112 at junction 1122. The
flexible nose 1120 is at least approximately 3 millimeters in
length and functions as a guidewire when the treatment wire 1103 is
inserted into a microcatheter 1105. In the embodiment illustrated
in FIG. 11, the flexible nose 1120 is a soft coil made of metal or
another suitable material known in the art. The flexible nose 1120
facilitates the delivery of the potted ultrasound radiating element
1112 through the microcatheter 1105 and into the vessel lumen of
the treatment site. Preferably, the flexible nose 1120 is tapered
in a manner so that the distal end of the nose has a smaller
diameter than the proximal end.
[0086] In use, a free end of a guidewire is percutaneously inserted
into the arterial system at a suitable first puncture site. The
guidewire is advanced through the vessels toward a treatment site,
such as, for example, a thrombotic occlusion in the middle cerebral
artery.
[0087] The microcatheter 1105 is thereafter percutaneously inserted
into the first puncture site and advanced along the guidewire
towards the treatment site using traditional over-the-guidewire
techniques. The catheter 1105 is advanced until the distal end 1199
of the catheter 1105 is positioned at or within the occlusion.
Preferably, the distal end 1199 includes radio opaque markers to
aid positioning the distal end 1199 within the treatment site.
[0088] The guidewire can then be withdrawn from the delivery lumen
1197 of the microcatheter 1105. As illustrated in FIG. 12, the
treatment wire 1103 is then inserted and advanced through the
microcatheter 1105 to the treatment site. The potted ultrasound
radiating element 1112 of the treatment wire 1103 is advanced
beyond the distal end 1199 of the microcatheter and into lumen of
the vessel. Once at the target site, the ultrasound radiating
element 1106 provides ultrasound energy.
[0089] Preferably, drugs 1124, including but not limited to drugs
having thrombolytic effects, are infused through the microcatheter
1105 and delivered into the vessel around the ultrasound radiating
element 1106 at the same time the ultrasound radiating element 1106
emits energy. It is believed that the transmission of ultrasound
energy at the treatment site enhances drug uptake and activity and
has other therapeutic effects. Preferably, the potted ultrasound
radiating element 1112 extends far enough away from the distal tip
1199 of the microcatheter 1105 to facilitate the infusion of drugs
(shown by arrow 1124) through the microcatheter 1105 and into the
vessel.
[0090] While the foregoing detailed description has described
several embodiments of the apparatus and methods of the present
invention, it is to be understood that the above description is
illustrative only and is not limiting of the disclosed invention.
It will be appreciated that the specific dimensions and
configurations can differ from those described above, and that the
methods described can be used within any biological conduit within
the body and remain within the scope of the present invention.
Thus, the invention is to be limited only by the claims that
follow.
* * * * *