US20040068189A1 - Ultrasound catheter with embedded conductors - Google Patents

Abstract

An ultrasound catheter comprises an elongate tubular body. The elongate tubular body has a proximal region and a distal region opposite the proximal region. The tubular body defines a central lumen having a central lumen diameter. The ultrasound catheter further comprises an elongate, hollow inner core extending through the central lumen. The elongate, hollow inner core has an inner core outer diameter that is less than or equal to the central lumen diameter. The ultrasound catheter further comprises an ultrasound radiating member positioned within the distal region of the tubular body and between the tubular body and the inner core. The ultrasound catheter further comprises at least two electrical conductors extending between the tubular body proximal region and the tubular body distal region. The at least two electrical conductors are positioned between the tubular body and the inner core. The at least two electrical conductors are electrically connected to the ultrasound radiating member. The at least two electrical conductors are wrapped around the inner core a plurality of times in a region between the ultrasound radiating member and the tubular body proximal region.

Description

RELATED APPLICATIONS
• J This application claims priority under 35 U.S.C. § 119(e) from U.S. Provisional Patent Application Serial No. 60/361,341, entitled “Small Vessel Catheter with Embedded Conductors” and filed Feb. 28, 2002. The entire disclosure of this priority document is hereby incorporated by reference in its entirety. In addition, the application is a continuation-in-part of U.S. patent application Ser. No. 10/309,417, entitled “Small Vessel Ultrasonic Catheter” and filed Dec. 3, 2002, which is hereby incorporated by reference in its entirety.[0001]
FIELD OF THE INVENTION
• 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.[0002]
BACKGROUND OF THE INVENTION
• 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, the entire disclosure of which is hereby incorporated by reference herein. 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.[0003]
• 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, the entire disclosure of which is hereby incorporated by reference herein. 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.[0004]
• 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, the entire disclosure of which is hereby incorporated by reference herein, 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.[0005]
• 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, the entire disclosure of which is hereby incorporated by reference herein).[0006]
• 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.[0007]
• 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.[0008]
SUMMARY OF THE INVENTION
• In accordance with the foregoing, it is desired to provide an ultrasound catheter having increased flexibility and maneuverability. Such features are advantageous when a treatment is to be performed in the peripheral vasculature, and are especially advantageous when a treatment is to be performed in small vessels, such as in the neurovascular system.[0009]
• As such, according to one embodiment of the present invention, an ultrasound catheter comprises an elongate tubular body. The elongate tubular body has a proximal region and a distal region opposite the proximal region. The tubular body defines a central lumen having a central lumen diameter. The ultrasound catheter further comprises an elongate, hollow inner core extending through the central lumen. The elongate, hollow inner core has an inner core outer diameter that is less than or equal to the central lumen diameter. The ultrasound catheter further comprises an ultrasound radiating member positioned within the distal region of the tubular body and between the tubular body and the inner core. The ultrasound catheter further comprises at least two electrical conductors extending between the tubular body proximal region and the tubular body distal region. The at least two electrical conductors are positioned between the tubular body and the inner core. The at least two electrical conductors are electrically connected to the ultrasound radiating member. The at least two electrical conductors are wrapped around the inner core a plurality of times in a region between the ultrasound radiating member and the tubular body proximal region.[0010]
• According to another embodiment of the present invention, an ultrasound catherter comprises an elongate tubular body. The elongate tubular body has a proximal region and a distal region opposite the proximal region. The tubular body defines a central lumen having a central lumen diameter. The ultrasound catheter further comprises an elongate, hollow inner core extending through the central lumen. The elongate, hollow inner core has an inner core outer diameter that is less than or equal to the central lumen diameter. The ultrasound catheter further comprises an ultrasound radiating member positioned within the distal region of the tubular body and between the tubular body and the inner core. The ultrasound catheter further comprises at least two electrical conductors extending between the tubular body proximal region and the tubular body distal region. The at least two electrical conductors are positioned between the tubular body and the inner core. The at least two electrical conductors are electrically connected to the ultrasound radiating member. The at least two electrical conductors are disposed substantially parallel to a catheter axis in a region between the ultrasound radiating member and the tubular body proximal region.[0011]
• According to another embodiment of the present invention, an apparatus comprises an elongate, hollow body. The elongate, hollow body has a proximal region, a distal region opposite the proximal region, a body thickness, and an inner lumen. The apparatus futher comprises an ultrasound radiating member positioned within the body thickness of the elongate, hollow body. The apparatus further comprises a plurality of elongate eletrical conductors extending between the elongate, hollow body proximal region and the ultrasound radiating member. The plurality of elongate electrical conductors are positioned within the body thickness of the elongate, hollow body.[0012]
BRIEF DESCRIPTION OF THE DRAWINGS
• 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.[0013]
• FIG. 2A is a cross-sectional view of a distal end of the ultrasound catheter of FIG. 1.[0014]
• FIG. 2B is a cross-sectional view of the ultrasound catheter taken through[0015]line2B-2B of FIG. 2A.
• FIG. 3 is an alternative embodiment of the ultrasound catheter including a stiffener at the distal tip.[0016]
• 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.[0017]
• 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.[0018]
• 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.[0019]
• 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.[0020]
• FIG. 7A is a top view of the distal end of an ultrasound catheter having a soft tip assembly.[0021]
• FIG. 7B is a cross-sectional view of the soft tip assembly taken through[0022]line7B-7B of FIG. 7A.
• FIG. 8 is a side view an ultrasound element attached to the distal end of a guidewire.[0023]
• FIG. 9 is a cross-sectional view of an ultrasound catheter used with the ultrasound element and guidewire of FIG. 8.[0024]
• 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.[0025]
• 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.[0026]
• FIG. 12 is a side view of a distal end of an ultrasound catheter that incorporates the treatment wire of FIG. 11.[0027]
• FIG. 13A is a partial cutaway view of one embodiment of an ultrasound catheter with embedded conductive wires that are spirally wrapped parallel to each other.[0028]
• FIG. 13B is a partial cutaway view of one embodiment of an ultrasound catheter with embedded conductive wires that are spirally wrapped into a unitary cable.[0029]
• FIG. 14 is a partial cutaway view of one embodiment of an ultrasound catheter with embedded conductive wires that are spirally wrapped in a nonparallel[0030]
• FIG. 15 is a partial cutaway view of one embodiment of an ultrasound catheter with embedded conductive wires that are disposed substantially parallel to the[0031]
• FIG. 16A illustrates a longitudinal cross-sectional view of an ultrasound catheter having internal surfaces that are electrically conductive.[0032]
• FIG. 16B illustrates a cross-sectional view of the ultrasound catheter of FIG. 16A taken along[0033]line16B-16B.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
• The advancement of an ultrasound catheter through a blood vessel to a treatment can be difficult and dangerous, particularly when the treatment site is located with 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 a 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.[0034]
• 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. Patent 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.[0035]
• 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 patents mentioned in this paragraph and the previous paragraph is hereby incorporated by reference herein and made a part of this specification.[0036]
• 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 of 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.[0037]
• 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.[0038]
Preferred Features of an Ultrasound Catheter
• Referring now to FIGS. 1 through 2B, for purposes of illustration, preferred embodiments of the present invention provide an[0039]ultrasound catheter100 that is particulary well suited for use within small vessels of the distal anatomy, such as, for example, in the remote, small diameter, neurovasculature in the brain.
• As shown in FIGS. 1 and 2A, the[0040]ultrasound catheter100 generally comprises a multi-componenttubular body102 having aproximal end104 and adistal end106. Thetubular body102 and other components of thecatheter100 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.
• Preferably, the[0041]tubular body102 can be divided into at least three sections of varying stiffness. The first section, which preferably includes theproximal end104, is generally more stiff than a second section, which lies between theproximal end104 and thedistal end106 of the catheter. This arrangement facilitates the movement and placement of thecatheter102 within small vessels. The third section, which includesultrasound radiating element124, is generally stiffer than the second section due to the presence of theultrasound radiating element124.
• 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.[0042]
• The elongate flexible[0043]tubular body102 comprises an outer sheath108 (see FIG. 2A) that is positioned upon aninner core110. In an embodiment particularly well suited for small vessels, theouter sheath108 comprises extruded PEBAX, PTFE, PEEK, PE, polymides, braided polymides and/or other similar materials. The distal end portion of theouter sheath108 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 theouter sheath108 has an outer diameter between about 2 and 5 French. More preferably, the distal end portion of theouter sheath108 has an outer diameter of about 2.8 French. In one preferred embodiment, theouter sheath108 has an axial length of approximately 150 centimeters.
• In other embodiments, the[0044]outer sheath108 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 thetubular body102. For enhanced pushability and torqueability, theouter sheath108 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 thetubular body102.
• The[0045]inner core110 defines, at least in part, adelivery lumen112, which preferably extends longitudinally along the entire length of thecatheter100. Thedelivery lumen112 has adistal exit port114 and aproximal axis port116. Referring again to FIG. 1, theproximal access port116 is defined bydrug inlet port117 of aback end hub118, which is attached to theproximal end104 of theother sheath108. The illustratedback end hub118 is preferably attached to acontrol box connector120, the utility of which will be described in more detail below.
• The[0046]delivery lumen112 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. Theinner core110 is preferably formed from polymide or a similar material which, in some embodiments, can be braided to increase the flexibility of thetubular body102.
• With particular reference to FIGS. 2A and 2B, the[0047]distal end106 of thecatheter102 preferably includes theultrasound radiating element124. In the illustrated embodiment, theultrasound radiating element124 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 theultrasound radiating element124 and the ultrasound energy can be transmitted via, for example, a wire to theultrasound radiating element124.
• In the embodiment illustrated in FIGS. 2A and 2B, the[0048]ultrasound radiating element124 is configured as a hollow cylinder. As such, theinner core110 can extend through the lumen of theultrasound radiating element124. Theultrasound radiating element124 can be secured to theinner core110 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.
• In other embodiments, the[0049]ultrasound radiating element124 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, theultrasound radiating element124 may comprise a plurality of smaller ultrasound radiating elements. The illustrated arrangement is the generally preferred configuration because it provides for enhanced cooling of theultrasound radiating element124. For example, in one preferred embodiment, a drug solution can be delivered through thedelivery lumen112. 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 theultrasound radiating element124. In another embodiment, a return path can be formed in thespace138 between the outer sheath and the inner core such that coolant from a coolant system can be directed through thespace138.
• The[0050]ultrasound radiating element40 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.
• As mentioned above, in the illustrated embodiment, ultrasound energy is generated from electrical power supplied to the[0051]ultrasound radiating element124. The electrical power can be supplied through thecontroller box connector120, which is connected to apair wires126,128 that extend through thecatheter body102. Theelectrical wires126,128 can be secured to theinner core110, lay along theinner core110 and/or extend freely in the space between theinner core110 and theouter sheath108. In the illustrated arrangement, thefirst wire126 is connected to the hollow center of theultrasound radiating element124 while thesecond wire128 is connected to the outer periphery of theultrasound radiating element124. Theultrasound radiating element124 is preferably, but is not limited to, a transducer formed of a piezolectic ceramic oscillator or a similar material.
• With continued reference to FIGS. 2A and 2B, the[0052]distal end104 of thecatheter100 preferably includes asleeve130, which is generally positioned about theultrasound radiating element124. Thesleeve130 is preferably constructed from a material that readily transmits ultrasound energy. Suitable materials for thesleeve130 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 thesleeve130 can be attached to theouter sheath108 with an adhesive132. To improve the bonding of the adhesive132 to theouter sheath108, ashoulder127 or notch may be formed in the outer sheath for attachment of the adhesive thereto. Preferably, theouter sheath108 and thesleeve130 have substantially the same outer diameter.
• In a similar manner, the distal end of the[0053]sleeve130 can be attached to atip134. In the illustrated arrangement, thetip134 is also attached to the distal end of theinner core110. 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.
• With continued reference to FIG. 2B, the[0054]catheter100 preferably includes at least onetemperature sensor136 along thedistal end106. Thetemperature sensor136 is preferably located on or near theultrasound radiating element124. 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 thecatheter body102 andback end hub118 and is operatively connected to a control box through thecontrol box connector120. 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 copending provisional application entitled CONTROL POD FOR ULTRASONIC CATHETER, Application Serial No. 60/336,630, filed Dec. 3, 2001, which is incorporated by reference in its entirety.
• In one exemplary application of the[0055]ultrasound catheter100 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.
• After advancing the guidewire to the treatment site, the[0056]catheter100 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. Thecatheter100 is advanced until thedistal end106 of thecatheter100 is positioned at or within the occlusion. Thedistal end106 of thecatheter100 may include one or more radiopaque markers (not shown) to aid in positioning thedistal end106 within the treatment site.
• After placing the catheter, the guidewire can then be withdrawn from the[0057]delivery lumen112. A drug solution source (not shown), such as a syringe with a Luer fitting, is attached to thedrug inlet port117 and thecontroller box connector120 is connected to the control box. As such, the drug solution can be delivered through thedelivery lumen112 and out thedistal access port114 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).
• The[0058]ultrasound radiating element124 is activated to emit ultrasound energy from thedistal end106 of thecatheter100. As mentioned above, suitable frequencies for theultrasound radiating element124 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, thecatheter100 is withdrawn from the treatment site.
Stiffening Component
• Referring again to FIG. 2A, because the diameter of the[0059]distal exit port114 is often relatively large compared with the diameter of the guidewire (not shown), a gap may exist between the inner rim of thetip134 and the guidewire. If sufficiently large, this gap may cause thetip134 of the catheter to catch or snag on an object along theexit port114. If thetip134 catches on an object, theexit port114 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.”
• FIG. 3 illustrates an embodiment adapted to reduce the likelihood of fish-mouthing wherein a[0060]circular stiffening component140 is provided along thedistal tip134. Thecircular stiffening component140 reduces the gap between thetip134 and the guidewire, and is preferably made of a stiff material, such as, for example, aluminum, that will prevent thetip134 from fish-mouthing. Additionally, if the guidewire is formed with a variable diameter, cooperation of the guidewire and thecircular stiffening component140 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 theexit port114 along thetip134. As seen in FIG. 3, this embodiment also includes a variation of the inner core110A having a flared end that may be inserted into acircumferential notch142 formed in thedistal tip134. Insertion of the flared end into the circumferential notch provides for enhanced structural integrity.
• In alternative embodiments, fish-mouthing may be prevented by increasing the thickness of the[0061]tip134, or by manufacturing thetip134 using a material with increased stiffness. In such embodiments, thetip134 will have decreased flexibility, and therefore will be less susceptible to fish-mouthing.
Flexible Joint
• 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[0062]outer sheath108 andsleeve130 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.
• In such embodiments, the used of an adhesive may be eliminated, and the proximal end of the[0063]sleeve130 may be attached to theouter sheath108 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.
• 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[0064]inner core410 includes acorrugated portion452 along the proximal element joint just proximal of theultrasound radiating element424. In such embodiments, aTeflon® liner450 may be adapted to surround the inner surface of thecorrugated portion452 of theinner core410 to prevent the guidewire from catching on the corrugations. Additionally, aflexible filler material456 and aflexible cover sleeve454 may be adapted to cover the exterior surface of thecorrugated portion452 of the catheter to prevent the catheter from catching on the interior walls of the vessel anatomy. Acorrugated portion452 of theinner core410 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 theinner core410, thecorrugated portion452 of theinner core410 will have enhanced flexibility and will thereby increase the flexibility of the ultrasound catheter.
• In still other embodiments, the rigidity of the proximal element joint may be further reduced by forming the[0065]inner core410 of thedelivery lumen412 of a material with increased flexibility and resistance to kinking. For example, theinner core410 of thedelivery lumen412 may comprise a Teflon®-lined polyimide shaft. Additionally, a coil or braid may be incorporated into thedelivery lumen412, thereby further reducing susceptibility to kinking without increasing the rigidity of the catheter.
• FIG. 5 illustrates yet another alternative embodiment wherein the rigidity of the proximal element joint[0066]548 is reduced by providing aouter sheath508 that includes an embeddedbraid560. Furthermore, theouter sheath508 is attached to thesleeve530 using a flexible exposedbraided portion558. Aflexible filler material556 and aflexible cover sleeve554 are used to bond theouter sheath508, thesleeve530 and the exposed braidedportion558 together. This embodiment provides the catheter with a flexible region just proximal to theultrasound radiating member524. In various preferred embodiments, the braided sections may be formed of high or low density polyethylenes, urethanes or nylons.
Shapeable Tip
• FIG. 6A illustrates yet another modified embodiment wherein the ultrasound catheter provides improved tracking over the[0067]guidewire602. Prolapsing of a guidewire is most likely to occur at small vessel radii, where theguidewire602 follows a sharp turn, and where the angle θ formed by the intersection between theguidewire602 and the catheter body is large. In order to reduce the incident angle θ between the guidewire and catheter body, atapered wire642 is provided along the exterior of theouter sheath608 for shaping the distal end of the catheter. The taperedwire642 may be set in a flexible potting orfiller material644, which is contained within aflexible sleeve646. The taperedwire642 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 taperedwire642 assists the physician in steering the catheter to follow theguidewire602 reliably around small vessel radii by reducing the angle θ formed by the intersection between theguidewire602 and the catheter body. The tapered wire is preferably provided in the region surrounding the ultrasound radiating element624. FIG. 6B illustrates the embodiment of FIG. 6A in use with the tip pre-formed for improved tracking over the guidewire.
Soft Tip Assembly
• 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.[0068]
• FIG. 7A illustrates an alternative embodiment wherein the distal end portion of an ultrasound catheter is provided with a soft tip assembly[0069]700. In the illustrated embodiment, the ultrasound catheter generally comprises anelongate shaft body702, anultrasound radiating element704, an elongatesoft tip706 and a connectingsleeve708. Thesoft tip706 of the catheter is constructed to be softer and more flexible than theshaft body702 for the purpose of minimizing or eliminating damage to the tissue along the inner wall of a blood vessel. In the illustrated embodiment, thesoft tip706 is configured as a substantially hollow member including adelivery lumen710. Thelumen710 may be used for receiving a guidewire and/or for delivering drugs to a treatment site. Preferably, theshaft body702 and thesoft tip706 have substantially the same outer diameter. Thedelivery lumen710 terminates at anexit port720 at the extreme distal tip of the soft tip assembly.
• Still referring to FIG. 7A, the[0070]ultrasound radiating element704 is provided at a location just distal to theshaft body702 and just proximal of thesoft tip710. Preferably, asmall gap712 is provided between theultrasound radiating element704 and theelongate body702 and also between theultrasound radiating element704 and thesoft tip706. In the illustrated embodiment, a single cylindricalultrasound radiating element704 is provided, however, in alternative embodiments, others variations may be used, such as, for example a plurality of smaller ultrasound radiating elements.
• In the illustrated embodiment, the[0071]shaft body702,ultrasound radiating element704 andsoft tip706 are secured together by thesleeve708. Theultrasound radiating element704 is contained within the lumen of thesleeve708. Theproximal end714 of thesleeve708 extends over the distal portion of theshaft body702. Thedistal end716 of thesleeve708 extends over the proximal end of thesoft tip706. In one embodiment, thesleeve708 is formed of heat shrink tubing. To maximize effectiveness of the ultrasound catheter, thesleeve708 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 throughline7B-7B.
• Referring again to FIG. 7A, the illustrated embodiment of the[0072]soft tip assembly706 is formed with a plurality of side holes718. The side holes718 are in communication with thedelivery lumen710 and are provided for enhancing the delivery of drugs to the treatment site. Using the side holes718, the therapeutic agent can be delivered radially at a location closer to theultrasound radiating element704. 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.
• 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.[0073]
• In operation, the ultrasound catheter is advanced over a guidewire that extends through the[0074]delivery lumen710. 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 thedelivery lumen710 used for the delivery of a therapeutic agent to the treatment site.
• 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.[0075]
Ultrasound Element on a Guidewire
• FIGS. 8 and 9 illustrate another modified embodiment of an[0076]ultrasound catheter850. As shown in FIG. 8, in this embodiment, anultrasound radiating element852 is connected to or mounted on adistal end854 of aguidewire856. In the illustrated arrangement, theultrasound radiating element852 is in the shape of a hollow cylinder. As such, theguidewire856 can extend through theultrasound radiating element852, which is positioned over theguidewire856. Theultrasound radiating element852 can be secured to theguidewire856 in any suitable manner, such as with an adhesive. In other embodiments, theultrasound radiating element856 can be of a different shape, such as, for example, a solid cylinder, a disk, a solid rectangle or a plate attached to theguidewire856. Theultrasound radiating element852 can also be formed from a plurality of smaller ultrasound elements.
• In the illustrated embodiment, ultrasound energy is generated from electrical power supplied to the[0077]ultrasound radiating element852. As such, theultrasound radiating element852 is connected to a pair ofwires860,862 that can extend through the catheter body. In the illustrated embodiment, thewires860,862 are preferably secured to theguidewire856 with thefirst wire860 is connected to the hollow center of theultrasound radiating element852 and thesecond wire862 connected to the outer periphery of theultrasound radiating element852. As with the previous embodiments, theultrasound radiating element852 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. Theultrasound radiating element852 and thewires860,862 are preferably covered with a thininsulating material857.
• FIG. 9 illustrates one embodiment of a[0078]catheter850 that can be used with theguidewire856 described above. In this embodiment, thecatheter850 includes anouter sheath866, which defines thedelivery lumen868. As such, the illustrated embodiment does not include an inner core. Thedelivery lumen868 includes adistal opening870. As will be explained below, in one arrangement, thedistal opening870 can be configured such that theguidewire856 and theultrasound radiating element852 can be withdrawn into thecatheter850 through thedistal opening870. In such an arrangement, adistal end872 of thecatheter850 preferably includes asleeve874, that is constructed from a material that readily transmits ultrasound energy as described above. In another arrangement, thedistal opening870 can be configured such thatultrasound radiating element852 can not be withdrawn into thecatheter850 through thedistal opening870. In such an arrangement, theultrasound radiating element852 is configured to operate outside thecatheter850 near thedistal opening870.
• In one embodiment, the[0079]distal end854 of theguidewire856 is percutaneously inserted into the arterial system at a suitable first puncture site. Theguidewire856 and theultrasound radiating element852 are advanced through the vessels towards a treatment site, which includes a thrombotic occlusion. Theguidewire856 is preferably then directed through the thrombotic occlusion.
• The[0080]catheter850 is thereafter percutaneously inserted into the first puncture site and advanced along theguidewire856 towards the treatment site using traditional over-the-iques. guidewire techniques. Thecatheter850 is advanced until the distal end of thecatheter856 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.
• In one embodiment, the[0081]guidewire856 can then be withdrawn until theultrasound radiating element852 is positioned within thedistal end874 of thecatheter850. In such an arrangement, thecatheter850 can include aproximal stop875 to aid the positioning of theultrasound radiating element852. In another embodiment, the guidewire can be withdrawn until theultrasound radiating element852 is located near or adjacent thedistal opening870. Thecatheter850 can then be operated as described above.
• 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[0082]catheter850 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. Thecatheter850 preferably is advanced until the distal end of thecatheter850 is positioned at or within the occlusion. The standard guidewire can then be withdrawn from the delivery lumen. Theguidewire856 andultrasound radiating element852 of FIG. 8 can then be inserted into the delivery lumen. In one embodiment, theultrasound radiating element852 is advanced until it is positioned in the distal end of thecatheter850. In another embodiment, theultrasound radiating element852 is advanced until it exits thedistal end870 of thedelivery lumen868. The catheter can then be operated as describe above.
• FIG. 10 illustrates yet another modified embodiment of an[0083]ultrasound catheter1000 that can be used with theguidewire1056 andultrasound radiating element1052, as described above. In this embodiment, theguidewire lumen1068 is defined by an inner sleeve ortube1002. Thedistal end1070 of thedelivery lumen1068 can be configured as described above for preventing or withdrawing theultrasound radiating element1052 into catheter1050. In the illustrated arrangement, thedelivery lumen1068 can be used to transport the drug solution. In another arrangement, thespace1004 between theinner core1002 and theouter sheath1066 can be used to transport the drug solution. In such an arrangement, theouter sheath1066 preferably includes one or more holes positioned at the distal end1072 of theouter sheath1066. The catheter can be advanced on theguidewire856 of FIG. 8 or a standard guidewire as described above.
Ultrasound Element on a Hypotube
• FIGS. 11 and 12 illustrate yet another embodiment of an[0084]ultrasound catheter1101 that is particularly well suited for use with small vessels of the distal anatomy. As shown in FIG. 12, this embodiment of theultrasound catheter1101 generally comprises atreatment wire1103 and amicrocatheter1105.
• FIG. 11 illustrates a preferred embodiment of a[0085]treatment wire1103. As shown in FIG. 11, in this embodiment, anultrasound radiating element1106 is connected to the distal tip of ahypotube1108. As discussed with reference to the small vessel catheters described above, the ultrasound radiating element can take many shapes and forms. Theultrasound radiating element1106 is potted in an insulating material either as a conformal coating or potted inside an outer sleeve. Thepotting1110 over theultrasound radiating element1106 sections is optimized for transmission of ultrasound energy. In the embodiment illustrated in FIG. 11, the width of the pottedultrasound radiating element1112 is approximately 0.018 inches. An epoxy or similar adhesive known in the catheter manufacturing field connects the pottedultrasound radiating element1112 with thehypotube1108 atjunction1114.
• The[0086]hypotube1108 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. Thehypotube1108 provides aninsulated lumen1116 through which one can runpower wires1118 for theultrasound radiating element1106 or wires for temperature sensors (not shown) in themicrocatheter1105. Themicrocatheter1105, into which thetreatment wire1103 is inserted, has a diameter greater than the width of the pottedultrasound radiating element1112.
• As shown in FIG. 11, in this embodiment, a[0087]flexible nose1120 is connected to the distal end of the pottedultrasound radiating element1112. An epoxy or similar adhesive known in the catheter manufacturing field connects theflexible nose1120 to the pottedultrasound radiating element1112 atjunction1122. Theflexible nose1120 is at least approximately 3 millimeters in length and functions as a guidewire when thetreatment wire1103 is inserted into amicrocatheter1105. In the embodiment illustrated in FIG. 11, theflexible nose1120 is a soft coil made of metal or another suitable material known in the art. Theflexible nose1120 facilitates the delivery of the pottedultrasound radiating element1112 through themicrocatheter1105 and into the vessel lumen of the treatment site. Preferably, theflexible nose1120 is tapered in a manner so that the distal end of the nose has a smaller diameter than the proximal end.
• 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.[0088]
• The[0089]microcatheter1105 is thereafter percutaneously inserted into the first puncture site and advanced along the guidewire towards the treatment site using traditional over-the-guidewire techniques. Thecatheter1105 is advanced until thedistal end1199 of thecatheter1105 is positioned at or within the occlusion. Preferably, thedistal end1199 includes radio opaque markers to aid positioning thedistal end1199 within the treatment site.
• The guidewire can then be withdrawn from the[0090]delivery lumen1197 of themicrocatheter1105. As illustrated in FIG. 12, thetreatment wire1103 is then inserted and advanced through themicrocatheter1105 to the treatment site. The pottedultrasound radiating element1112 of thetreatment wire1103 is advanced beyond thedistal end1199 of the microcatheter and into lumen of the vessel. Once at the target site, theultrasound radiating element1106 provides ultrasound energy.
• Preferably,[0091]drugs1124, including but not limited to drugs having thrombolytic effects, are infused through themicrocatheter1105 and delivered into the vessel around theultrasound radiating element1106 at the same time theultrasound radiating element1106 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 pottedultrasound radiating element1112 extends far enough away from thedistal tip1199 of themicrocatheter1105 to facilitate the infusion of drugs (shown by arrow1124) through themicrocatheter1105 and into the vessel.
Overview of Ultrasound Catheter with Embedded Conductors
• In certain embodiments, wherein an ultrasound radiating member is positioned between an inner elongate tubular body and an outer elongate tubular body, it is desired to pass elongate electrical conductors to the ultrasound radiating member from the proximal end of the catheter, thereby allowing an externally-generated driving signal to be provided to the ultrasound radiating member. In addition, in embodiments wherein a temperature sensor is positioned in the distal region of the catheter, it is desired to pass one or more elongate electrical conductors to the temperature sensor from the proximal end of the catheter, thereby allowing a distal temperature signal to be monitored at the proximal end of the catheter. The configuration of such elongate electrical conductors can be manipulated to affect the stiffness, torqueability, pushability, flexibility and other mechanical parameters of the catheter, thereby affecting accessibility of remote targets in the patient's vasculature.[0092]
• Such embedded conductor configurations are discussed in greater detail in this section. These embodiments are particularly well-suited for use with small vessels of the distal anatomy, such as, for example, the vessels of the neurovascular system. However, such embodiments are also well-suited for the treatment of long segment peripheral arterial occlusions.[0093]
• Referring now to FIG. 13A, an[0094]ultrasonic catheter1200 generally comprises a multi-componenttubular body1201 having aproximal end1204 and adistal end1202. Thetubular body1201 and other components of thecatheter1200 can be manufactured in accordance with any of a variety of techniques well known in the catheter manufacturing field, and as explained above.
• The[0095]ultrasonic catheter1200 also comprises one or moreultrasound radiating members1240 at itsdistal end1202. Suitable material dimensions for theultrasound radiating member1240 can be readily selected taking into account the natural and anatomical dimensions of the treatment site and of the desired percutaneous access site, as explained above. In other embodiments, theultrasonic catheter1200 further comprises a temperature sensor (not shown) positioned within the catheter distal region, as described above. In one preferred embodiment of anultrasonic catheter1200, acentral lumen1251 can be concentrically placed over a guidewire (not shown) which has been previously navigated to the target area under, for example, fluoroscopic localization by a skilled surgeon or medical practitioner.
• The[0096]ultrasonic catheter1200 generally comprises one or more electrically conductive wires orfibers1206,1208 that extend along the length of thecatheter1200. In certain embodiments, theconductive wires1206,1208 generally reside within thewall1210 of thetubular body1201. In such embodiments, thewall1210 of thetubular body1201 comprises aninner portion1212 and anouter portion1214. In such embodiments, theconductive wires1206,1208 can be located in between theinner portion1212 andouter portion1214 of thewall1210.
• The[0097]inner portion1212 provides a barrier against the contents of thecentral lumen1251, such as, for example, therapeutic drugs infused through thecentral lumen1251 and out thedistal end1202 of the catheter to a treatment site within the patient's vasculature. Theouter portion1214 provides a barrier against the environment in which thecatheter1200 resides, which may include, for example, blood or other bodily fluids.
• The[0098]inner portion1212 andouter portion1214 of thewall1210, and thewall1210 in general, with the exception of theconductive wires1206,1208 embedded in thewall1210, is made of insulating material, such as, for example, polyimide, high or low density polyethylenes, urethanes, nylons, and the like. Consequently, theconductive wires1206,1208 are electrically isolated from thecentral lumen1251 and the environment in which thecatheter1200 resides.
• The[0099]conductive wires1206,1208 are also preferably electrically isolated from each other. In one embodiment, thewires1206,1208 are arranged and configured in a manner to prevent contact between them. For example, thewires1206,1208 may be arranged along and/or around the central lumen in a manner which prevents any contact between thewires1206,1208. Also, electrically insulating material may placed between thewires1206,1208 to prevent contact between them. In another embodiment, thewires1206,1208 are covered with insulating coating material either in addition to or in lieu of placing insulating material between thewires1206,1208 or making thewall1210 from insulating material.
• The physical configuration or layout of the[0100]conductive wires1206 and1208 embedded within thewall1210 of thetubular body1201 can be adjusted to determine the mechanical attributes of thecatheter1200. Theconductive wires1206,1208 may be arranged in various architectures such as, for example, linear arrays, weaving, spiraling, and other patterns which modulate stiffness, torquability, pushability, flexibility and other mechanical parameters of the catheter which relate to accessibility of remote targets.
• In one embodiment, shown in FIG. 13A, both[0101]conductive wires1206,1208 spiral around thecentral lumen1251 and remain substantially parallel to each other at all times along the length of thecatheter1200. In a modified embodiment, thewires1206,1208 are covered with insulating coating material. In another modified embodiment, illustrated in FIG. 13B, theconductive wires1206,1208 are covered with insulating coating material or separated with insulating material and are contained in aunitary cable1216. In such embodiments, thecable1216 spirals around thecentral lumen1251 along the length of thecatheter1200.
• In another embodiment, illustrated in FIG. 14, the[0102]conductive wires1206,1208 are covered with insulating coating material and are spiraled in opposite directions, thereby forming a helix or helical pattern around thecentral lumen1251. In forming a helical pattern, thewires1206,1208 cross each other, but remain electrically isolated from each other due to the insulating coating material around each wire.
• In another embodiment, illustrated in FIG. 15, the[0103]conductive wires1206,1208 run in a generally straight line along the length of thecatheter1200, and do not spiral around thecentral lumen1251 or cross each other. In such embodiments, the wires12606,12608 can optionally be covered with an insulating coating material.
• In a modified embodiment, illustrated in FIGS. 16A and 16B, the ultrasound catheter comprises an outer[0104]tubular body1400 surrounding aninner core1402. Theinner core1402 defines acentral lumen1408 that can be used to pass a guidewire, a cooling fluid or a therapeutic compound through the ultrasonic catheter. In a distal region of the ultrasound catheter, a tubularultrasound radiating member1404 is positioned between the outertubular body1400 and theinner core1402. In regions proximal to theultrasound radiating member1404, the outertubular body1400 and theinner core1402 are separated by an insulatinglayer1406. Preferably, the inner coreouter surface1410 and the outer tubular bodyinner surface1412 are electrically conductive, and are electrically connected to opposite poles of a power supply (not shown). Such electrically conductive surfaces can be created by depositing an electrically conductive material onto the desired surface.
• In such embodiments, the conductive surfaces are separated by the insulating[0105]layer1406 along the length of the catheter, and the presence of theultrasound radiating member1404 in the catheter distal region completes the electric circuit. In particular, because opposite surfaces of the ultrasound radiating member contact conductive surfaces ofopposite polarity1410,1412, a voltage difference is created across the ultrasound radiating member, thereby causing ultrasonic vibrations to be created.
• Such embodiments allow the[0106]ultrasound radiating member1404 to be driven while eliminating any wires passing along the catheter body, such as illustrated in FIGS. 13A through 15. Elimination of wiring in the catheter body reduces manufacturing costs and reduces overall catheter dimensions, thereby increasing catheter maneuverability. Elimination of wiring can also increase catheter flexibility. Thus, in applications where the ultrasound catheter is to be passed through a small or tortuous portion of the vasculature, it may be desired to use such embodiments.
• Small vessel ultrasonic catheters with conducting wires or fibers embedded in the walls of the catheter, as described above, can be assembled in a number of ways. See, for example, U.S. Pat. Nos. 4,277,432 and 6,030,371, both of which are incorporated by reference herein. In one method, the catheter is made from tubing which is fabricated from a polymer material that is extruded through a dye in a molten state and that is solidified while being drawn. In one preferred embodiment of the present invention, an electrically insulating material is extruded through the dye.[0107]
• Conventionally, manufacturing equipment is used to co-extrude polymer support fibers, such as, for example, Kevlar, into the tubing wall in a linear, spiral, or woven pattern. In certain embodiments of the present invention, electrically conductive wires or fibers are used in lieu of polymer support fibers. Examples of conductive fibers include, but are not limited to, copper, carbon, steel, and stainless steel. In a modified embodiment, the conductive fibers are pre-coated with an insulating coating before they are co-extruded.[0108]
• In another method of assembling small vessel catheters with conducting wires or fibers embedded in the walls of the catheter, the wires are sandwiched between two concentric tubes, an inner tube and an outer tube, both of which initially have approximately half the wall thickness of the final assembled catheter. The inner diameter of the inner tube determines the diameter of the final assembled catheter. The inner diameter of the outer tube is significantly greater than the outer diameter of the inner tube. For example, the inner and outer tubes can be made from an electrically isolating material.[0109]
• In such embodiments, the catheter is assembled by winding or placing conductive fiber or wire over the inner tube; concentrically translating the outer tube over the inner tube and the fiber wrapping or abutting the inner tube; and radially shrinking the outer tube onto the inner tube such that the conductive fiber is trapped between the inner and outer tubes. In a modified embodiment, the conductive fibers are pre-coated with an insulating coating before they are incorporated into the above described sandwich construction.[0110]
• As described above, the various configurations and arrangements of the elongate electrical conductors described herein can be used regardless of whether such elongate electrical conductors are connected to an ultrasound radiating member or a temperature sensor at the catheter distal end.[0111]
CONCLUSION
• 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 not limiting of the disclosed invention. It will be appreciated that the specific dimensions of the various catheters and guidewires 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 which follow.[0112]

Claims (38)

We claim:

1. An ultrasound catheter comprising:

an elongate tubular body having a proximal region and a distal region opposite the proximal region, the tubular body defining a central lumen having a central lumen diameter;

an elongate, hollow inner core extending through the central lumen and having an inner core outer diameter that is less than or equal to the central lumen diameter;

an ultrasound radiating member positioned within the distal region of the tubular body and between the tubular body and the inner core;

at least two electrical conductors extending between the tubular body proximal region and the tubular body distal region, the at least two electrical conductors positioned between the tubular body and the inner core, and electrically connected to the ultrasound radiating member, wherein the at least two electrical conductors are wrapped around the inner core a plurality of times in a region between the ultrasound radiating member and the tubular body proximal region.

2. The ultrasound catheter ofclaim 1, further comprising:

a temperature sensor positioned adjacent the distal region of the elongate tubular body; and

at least one temperature sensor wire extending between the tubular body proximal region and the tubular body distal region, wherein at least a portion of the at least one temperature sensor wire is positioned between the tubular body and the inner core, and wherein the at least one temperature sensor wire is electrically connected to the temperature sensor.

3. The ultrasound catheter ofclaim 1, wherein the at least two electrical conductors are substantially parallel in a region between the ultrasound radiating member and the tubular body proximal region.

4. The ultrasound catheter ofclaim 3, wherein the at least two electrical conductors are integrated into a unitary cable.

5. The ultrasound catheter ofclaim 1, wherein the at least two electrical conductors do not cross paths in a region between the ultrasound radiating member and the tubular body proximal region.

6. The ultrasound catheter ofclaim 5, wherein the at least two electrical conductors are integrated into a unitary cable.

7. The ultrasound catheter ofclaim 1, wherein the at least two electrical conductors are wrapped around the inner core in opposite directions.

8. The ultrasound catheter ofclaim 1, wherein the at least two electrical conductors comprise electrically conductive fibers.

9. An ultrasound catheter comprising:

an elongate tubular body having a proximal region and a distal region opposite the proximal region, the tubular body defining a central lumen having a central lumen diameter;

an elongate, hollow inner core extending through the central lumen and having an inner core outer diameter that is less than or equal to the central lumen diameter;

an ultrasound radiating member positioned within the distal region of the tubular body and between the tubular body and the inner core;

at least two electrical conductors extending between the tubular body proximal region and the tubular body distal region, the at least two electrical conductors positioned between the tubular body and the inner core, and electrically connected to the ultrasound radiating member, wherein the at least two electrical conductors are disposed substantially parallel to a catheter axis in a region between the ultrasound radiating member and the tubular body proximal region.

10. The ultrasound catheter ofclaim 9, further comprising:

a temperature sensor positioned adjacent the distal region of the elongate tubular body; and

at least one temperature sensor wire extending between the tubular body proximal region and the tubular body distal region, wherein at least a portion of the at least one temperature sensor wire is positioned between the tubular body and the inner core, and wherein the at least one temperature sensor wire is electrically connected to the temperature sensor.

11. The ultrasound catheter ofclaim 9, wherein the ultrasound catheter comprises two electrical conductors which are disposed at substantially radially opposite points around the inner core.

12. The ultrasound catheter ofclaim 9, wherein the at least two electrical conductors comprise electrically conductive fibers.

13. An apparatus comprising:

an elongate, hollow body having a proximal region, a distal region opposite the proximal region, a body thickness, and an inner lumen;

an ultrasound radiating member positioned within the body thickness of the elongate, hollow body; and

a plurality of elongate electrical conductors extending between the elongate, hollow body proximal region and the ultrasound radiating member, and positioned within the body thickness of the elongate, hollow body.

14. The apparatus ofclaim 13, further comprising:

a temperature sensor positioned adjacent the elongate, hollow body distal region; and

at least one temperature sensor wire extending between the elongate, hollow body proximal region and the temperature sensor, and positioned within the body thickness of the elongate, hollow body.

15. The apparatus ofclaim 13, wherein the plurality of electrical conductors are substantially parallel in a region between the ultrasound radiating member and the elongate, hollow body proximal region.

16. The apparatus ofclaim 15, wherein the plurality of electrical conductors are integrated into a unitary cable.

17. The apparatus ofclaim 13, wherein the plurality of electrical conductors do not cross paths in a region between the ultrasound radiating member and the elongate, hollow body proximal region.

18. The apparatus ofclaim 17, wherein the plurality of electrical conductors are integrated into a unitary cable.

19. The apparatus ofclaim 13, wherein the plurality of electrical conductors are wrapped around the inner core in opposite directions.

20. The ultrasound catheter ofclaim 13, wherein the plurality of electrical conductors comprise electrically conductive fibers.

21. A method comprising:

maneuvering a guidewire through a patient's vasculature, such that a guidewire distal region is adjacent to a treatment site;

passing an elongate tubular body over the guidewire, the elongate tubular body having a distal region, a proximal region opposite the distal region and a tubular ultrasound radiating member mounted to the elongate tubular body distal region, such that the ultrasound radiating member is adjacent the treatment site;

withdrawing the guidewire from the elongate tubular body;

passing an electronic driving signal to the ultrasound radiating member to cause the ultrasound radiating member to deliver ultrasonic energy to the treatment site;

passing a therapeutic compound through the elongate tubular body to the treatment site, such that a quantity of therapeutic compound delivered to the treatment site is exposed to ultrasonic energy.

22. The method ofclaim 21, wherein the ultrasound radiating member is positioned within the elongate tubular body.

23. The method ofclaim 21, further comprising sensing a temperature at the treatment site.

24. A method of manufacturing an ultrasonic catheter comprising:

providing an inner tube having an inner diameter sufficient to accommodate a guidewire;

mounting a tubular ultrasound radiating member around a distal region of the inner tube;

positioning a first and a second electrical conductor along the inner tube, such that the first electrical conductor contacts an inner side of the ultrasound radiating member, and the second electrical conductor contacts an outer side of the ultrasound radiating member;

concentrically translating an outer tube over the inner tube and the ultrasound radiating member; and

radially shrinking the outer tube onto the inner tube.

25. The method ofclaim 24, further comprising:

mounting a temperature sensor adjacent to the distal region of the inner tube; and

positioning at least one temperature sensor wire along the inner tube, such that the temperature sensor wire is electrically connect to the temperature sensor.

26. The method ofclaim 24, wherein the first and second electrical conductors are positioned along the inner tube in a substantially parallel configuration.

27. The method ofclaim 26, wherein the first and second electrical conductors are positioned along the inner tube at substantially radially opposite points.

28. The method ofclaim 24, further comprising integrating the first and second electrical conductors into a unitary cable.

29. The method ofclaim 24, wherein the first and second electrical conductors are wrapped around the inner core in opposite directions.

30. The method ofclaim 24, further comprising connecting the first and second electrical conductors to opposite poles of a power supply at a proximal end of the ultrasonic catheter.

31. An apparatus comprising:

an elongate tubular body having a proximal region and a distal region opposite the proximal region, the tubular body defining a central lumen having a central lumen surface that is electrically conductive;

an elongate, hollow inner core extending through the central lumen and having an inner core outer surface that is electrically conductive;

an ultrasound radiating member positioned within the distal region of the tubular body and between the tubular body and the inner core, such that the tubular body conductive surface and the inner core conductive surface are both in electrical contact with the ultrasound radiating member; and

an insulating sleeve positioned between the tubular body and the inner core in a region proximal to the ultrasound radiating member.

32. The apparatus ofclaim 31, further comprising a temperature sensor positioned adjacent the elongate tubular body distal region.

33. The apparatus ofclaim 31, wherein the tubular body conductive surface and the inner core conductive surface are electrically connected to opposite poles of a power supply.

34. The apparatus ofclaim 31, further comprising a plurality of ultrasound radiating members positioned between the tubular body and the inner core.

35. The apparatus ofclaim 34, further comprising an insulating sleeve positioned between the tubular boy and the inner core in regions between the plurality of ultrasound radiating members.

36. The apparatus ofclaim 31, wherein the conductive surfaces comprise metallic fibers disposed on the central lumen surface or the inner core outer surface.

37. The apparatus ofclaim 36, wherein the metallic fibers comprise copper.

38. An ultrasound catheter comprising:

an elongate tubular body having a proximal region and a distal region opposite the proximal region, the tubular body defining a central lumen having a central lumen diameter;

an elongate, hollow inner core extending through the central lumen and having an inner core outer diameter that is less than or equal to the central lumen diameter;

an ultrasound radiating member positioned within the distal region of the tubular body and between the tubular body and the inner core;

a temperature sensor positioned adjacent the distal region of the elongate tubular body; and

at least one temperature sensor wire extending between the tubular body proximal region and the tubular body distal region, wherein at least a portion of the at least one temperature sensor wire is positioned between the tubular body and the inner core, and wherein the at least one temperature sensor wire is electrically connected to the temperature sensor.

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