Patent Application
20050215942
The present invention in certain embodiments relates generally to an ultrasound catheter, and specifically to an ultrasound catheter having a variable flexibility along the catheter body.
Ultrasonic energy can be used to enhance the delivery and effect of various therapeutic compounds. Often, an ultrasound catheter delivers ultrasonic energy and/or a therapeutic compound to a treatment site within a patient's vasculature. 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 ultrasonic energy. The ultrasound catheter can include a delivery lumen for delivering the therapeutic compound to the treatment site. In this manner, ultrasonic energy can be delivered to the treatment site to enhance the effect and/or delivery of the therapeutic compound.
For example, in one 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, for example, 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, ultrasonic energy is emitted into the dissolution compound and/or the surrounding tissue. In other applications, ultrasound catheters can be used for other purposes, such as delivering and activating light activated drugs with ultrasonic energy. See, for example, U.S. Pat. No. 6,176,842.
Generally, conventional ultrasound catheters are not well adapted for effective use within small blood vessels, such as blood vessels located in the distal anatomy or in the brain. This is often the result of several factors. For example, the distal end portion of the catheter, on which the ultrasound assembly is usually located, is relatively rigid and therefore often lacks sufficient flexibility for navigation through difficult regions of the distal anatomy. In particular, this distal rigidity is generally attributable to the ultrasound radiating member mounted in the distal region of the catheter. Even in an ultrasound assembly having a single ultrasound radiating member, the increased rigidity along the length of the ultrasound radiating member can adversely effect catheter maneuverability. Similarly, the minimum diameter vessel through which an ultrasound catheter can be passed depends, at least in part, on the outer diameter of the ultrasound radiating member. Furthermore, various wires must extend through the catheter to provide power to the ultrasound radiating member. In addition, the ultrasound catheter is typically provided with an inner member further increasing the stiffness of the catheter.
Furthermore, it is difficult to manufacture an ultrasound catheter having a sufficiently small diameter for use in small vessels while still providing the catheter with adequate “pushability” and “torqueability” Likewise, it is difficult to manufacture an ultrasound radiating member having sufficiently small dimensions for use in small vessels while still being capable of generating sufficient quantities of acoustic energy to enhance lysis at the treatment site. Still further, the distal tip of an ultrasound catheter can easily damage the fragile walls of small vessels in the patient's vasculature.
Accordingly, certain embodiments of an improved ultrasound catheter disclosed herein are capable of safely and effectively navigating small blood vessels, such as the main and subsequent branches of the middle cerebral artery. Such an improved catheter is also capable of delivering adequate ultrasonic energy to achieve a desired therapeutic effect. The embodiments described herein illustrate various features of such an improved ultrasound catheter.
One embodiment of the present invention comprises an ultrasound catheter configured to be advanced into a patient's neurovascular system. The catheter includes an elongate outer sheath and an elongate hollow inner core. The elongate outer sheath defines a central lumen that extends longitudinally from an outer sheath proximal region to an outer sheath distal region. The elongate hollow inner core is positioned in the central lumen. The inner core defines a utility lumen configured to receive a guidewire. The inner core has a distal region that terminates at a point that is proximal to the outer sheath distal region. The inner core comprises a reinforcing member that extends along at least a portion of the inner core. The reinforcing member is configured to reduce ovalization of the inner core as the catheter is bent. A tubular inner support member is coupled to the inner core distal region. A tubular outer support member is coupled to the outer sheath distal region. An ultrasound radiating member has an inner passage. The ultrasound radiating member is positioned generally the between the inner and outer support members, such that the inner support member passes through the hollow inner core and the outer support member is positioned over an outer surface of the ultrasound radiating member.
Another embodiment of the invention comprises an neurovascular catheter. The catheter includes a tubular body having a proximal end and a distal end. The tubular body comprises an inner tubular component and an outer tubular component. The outer tubular component has a proximal region, a distal region end and a lumen extending therethrough. The inner tubular component is positioned within the lumen of the outer tubular component and extends from the proximal region to distal region of the outer tubular component. The inner tubular component forms, at least in part a utility lumen, that extends from proximal end of the tubular body to the distal end of the tubular body. The inner tubular body is formed at least in part from a composite tube comprising an inner member. A reinforcing coil surrounds the inner member, and an outer member covers the reinforcing coil. At least one ultrasound radiating member is positioned generally between the outer tubular component and the inner tubular component at the distal end of the tubular body. A least one electrical wire is operatively connected to the ultrasound radiating member. The at least one electrical wire extends at least partially through a space between the outer tubular component and the inner tubular component.
Another embodiment of the invention comprises a catheter having a distal end and a proximal end. The catheter comprises an elongate outer sheath and an enlogate inner sheath. The elongate outer sheath has an exterior surface. The distal end portion of said outer sheath has an outer diameter of less than about 5 French for advancement through a small blood vessel. The outer sheath defines a central lumen extending longitudinally therethrough. An elongate inner core extends through said central lumen of said outer sheath and terminates at an exit port located at the distal end of the catheter. The inner core defines a utility lumen adapted to receive a guidewire lumen. An ultrasound member is positioned at the distal end of the catheter body generally between the outer sheath and the inner core. A guidewire is configured to be slideably received within the utility lumen for advancement of the catheter to a treatment site. The guidewire having a diameter that is less than or equal to about 0.017 inches. The catheter is configured such that the catheter can be subjected to a 180 degree bend having a radius of less than about 10 mm while still permitting the catheter to slide over the guidewire.
In one embodiment of the present invention, a method of manufacturing an ultrasound catheter comprises providing an elongate outer sheath that defines a central lumen extending longitudinally from an outer sheath proximal region to an outer sheath distal region. The method further comprises providing a plurality of elongate electrical conductors within the central lumen. The method further comprises positioning an elongate inner core in the central lumen, such that the plurality of electrical conductors are positioned between the inner core and the outer sheath. The method further comprises coupling a tubular inner support member to a distal region of the elongate inner core. The method further comprises mounting an ultrasound radiating member to the inner support member. The ultrasound radiating member includes a hollow inner core through which the inner support member is positioned. The method further comprises coupling a tubular outer support member to a distal region of the elongate outer sheath. The tubular outer support member is positioned over an outer surface of the ultrasound radiating member.
Introduction.
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. Accessing the treatment site may involve navigating a tortuous path around difficult bends and turns, such as the main and subsequent branches of the middle cerebral artery. During advancement through the vasculature, bending resistance along the distal end portion of the catheter can limit the ability of the catheter to make small radius 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, an improved ultrasound catheter design having variable flexibility and/or stiffness along the length of the catheter body will allow a physician to more easily navigate difficult turns in small blood vessels while reducing trauma and/or damage along the inner walls of the blood vessels.
Certain embodiments 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. Such embodiments can be used to enhance the therapeutic effects of drugs, medication, pharmacological agents and other therapeutic compounds at a treatment site within the body. See, for example, U.S. Pat. Nos. 5,318,014; 5,362,309; 5,474,531; 5,628,728; 6,001,069; and 6,210,356. Certain embodiments described herein 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, certain embodiments described herein can be used in other therapeutic applications, such as, for example, performing gene therapy (see, for example, U.S. Pat. No. 6,135,976), activating light activated drugs for producing targeted tissue death (see, for example, U.S. Pat. No. 6,176,842) and causing cavitation and/or controlled cavitation to produce various desirable biological effects (see, for example, U.S. Pat. No. RE36,939). Moreover, such therapeutic applications can be used in wide variety of locations within the body, such as, for example, in other parts of the circulatory system, in solid tissues, in duct systems and in body cavities. The ultrasound catheters disclosed herein, and variations thereof, can be used in other medical applications, such as, for example, diagnostic and imaging applications. The contents of the patents referenced above are hereby incorporated by reference herein.
Ultrasound catheters and methods disclosed herein, and similar variations thereof, can also be used in applications wherein the ultrasonic energy provides a therapeutic effect by itself. For example, ultrasonic energy can be effective in preventing and/or reducing stenosis and/or restenosis; causing tissue ablation, abrasion or disruption; promoting temporary or permanent physiological changes in intracellular or intercellular structures; and rupturing micro-balloons or microbubbles for drug delivery. See, for example, U.S. Pat. Nos. 5,269,291 and 5,431,663, which are hereby incorporated by reference herein. In addition, the methods and devices disclosed herein can also be used in applications that do not require the use of a catheter. For example, the methods and devices disclosed herein can be used to enhance hyperthermic drug treatment or to cause transdermal enhancement of the therapeutic effects of drugs, medication, pharmacological agents, or other therapeutic compounds at a specific site within the body. The methods and devices disclosed herein can also be used to provide a therapeutic or diagnostic effect without the use of a therapeutic compound. See, for example, U.S. Pat. Nos. 4,821,740; 4,953,565; 5,007,438 and 6,096,000, the contents which are hereby incorporated by reference herein.
As used herein, the term “ultrasonic energy” is used broadly, and includes its ordinary meaning, and further includes mechanical energy transferred through pressure or compression waves with a frequency greater than about 20 kHz. In one embodiment, the waves of the ultrasonic energy have a frequency between about 500 kHz and about 20 MHz, and in another embodiment the waves of ultrasonic energy have a frequency between about 1 MHz and about 3 MHz. In yet another embodiment, the waves of ultrasonic energy have a frequency of about 3 MHz.
As used herein, the term “catheter” is used broadly, and include its ordinary meaning, and further includes an elongate flexible tube configured to be inserted into the body of a patient, such as, for example, a body cavity, duct or vessel.
As used herein, the term “therapeutic compound” refers broadly, in addition to its ordinary meaning, to a drug, medicament, dissolution compound, genetic material, or any other substance capable of effecting physiological functions. Additionally, any mixture comprising any such substances is encompassed within this definition of “therapeutic compound”.
As used herein, the term “end” refers, in addition to its ordinary meaning, to a region, such that “proximal end” includes “proximal region”, and “distal end” includes “distal region”.
As used herein, the term “proximal element joint” refers generally, and in addition to its ordinary meaning, to a region where a proximal portion of an ultrasound radiating member is attached to other components of an ultrasound catheter.
Exemplary embodiments of an ultrasound, drug delivery catheter.
As shown in
The tubular body 102 can be divided into multiple sections of varying stiffness. For example, a first section, which 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. A third section, which includes at least one ultrasound radiating member 124, is generally stiffer than the second section due to the presence of the ultrasound radiating member 124.
In the exemplary embodiments described herein, the assembled ultrasound catheter 100 has sufficient structural integrity, or “pushability,” to permit the catheter to be advanced through a patient's vasculature to a treatment site without significant buckling or kinking. In addition, the catheter can transmit torque (that is, the catheter has “torqueability”), thereby allowing the distal portion of the catheter to be rotated into a desired orientation by applying a torque to the proximal end 104.
Referring now to
In other embodiments, the outer sheath 108 can be formed from a braided and/or coiled tubing comprising, for example, high or low density polyethylenes, urethanes, nylons, and so forth. Such a configuration enhances the flexibility of the tubular body 102. For enhanced pushability and torqueability, the outer sheath 108 can be formed with a variable stiffness from the proximal to the distal end. To achieve this, a stiffening member can be included along the proximal end of the tubular body 102. In one exemplary embodiment, the pushability and flexibility of the tubular body 102 are controlled by manipulating the material and thickness of the tubular body 102, while the torqueability, kink resistance, distortion (also referred to as “ovalization”) and burst strength of the tubular body 102 are controlled by incorporation of braiding and/or coiling along or into the tubular body 102.
In one particular embodiment, the outer tubular member 108 comprises a PTFE layer that surrounds a Teflon inner layer. As mentioned above, the outer tubular member 108 generally tapers from the proximal end to the distal end. In one embodiment, the proximal end of the outer member is reinforced with reinforcement member (e.g., a stainless steel flat wire coil) positioned between the PTFE and Teflon layers. A Tensile fiber (e.g., Kevlar or Vectron) may also be positioned between the layers to add tensile strength to the catheter.
The inner core 110 at least partially defines a delivery lumen 112. In an exemplary embodiment, the delivery lumen 112 extends longitudinally along substantially the entire length of the catheter 100. The delivery lumen 112 comprises a distal exit port 114 and a proximal access port 116. Referring again to
In an exemplary embodiment, the delivery lumen 112 is configured to receive a guide wire (not shown). In one embodiment, the guidewire has a diameter of approximately 0.008 inches to approximately 0.012 inches. In another embodiment, the guidewire has a diameter of about 0.010 inches. In an exemplary embodiment, the inner core 110 comprises polyimide or a similar material which, in some embodiments, can be braided and/or coiled to increase the flexibility of the tubular body 102.
Referring now to the exemplary embodiment illustrated in
As illustrated in
In other embodiments, the ultrasound radiating member 124 has different shape. For example, the ultrasound radiating member 124 can be shaped as a solid rod, a disk, a solid rectangle or a thin block. In still other embodiments, the ultrasound radiating member 124 comprises a plurality of smaller ultrasound radiating elements. The embodiments illustrated in
In an exemplary embodiment, the ultrasound radiating member 124 is selected to produce ultrasonic energy in a frequency range adapted for a particular application. Suitable frequencies of ultrasonic 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 about 20 MHz, and in another embodiment, the frequency is between about 1 MHz and about 3 MHz. In yet another embodiment, the ultrasonic energy has a frequency of about 3 MHz.
For example, in one embodiment, the dimensions of the ultrasound radiating member are selected to provide a ultrasound radiating member that is capable of generating sufficient acoustic energy to enhance lysis without significantly adversely affecting catheter maneuverability.
As described above, in the embodiment illustrated in
In the exemplary embodiment illustrated in
Still referring to the exemplary embodiment illustrated in
As illustrated in
In embodiments wherein multiple ultrasound radiating members are positioned in the catheter distal region, a plurality of temperature sensors can be positioned adjacent to the ultrasound radiating members. For example, in one such embodiment, a temperature sensor is positioned on or near each of the multiple ultrasound radiating members.
Exemplary Embodiments of Use
In an exemplary method, the ultrasound catheter 100 can be used to remove an occlusion from a small blood vessel. In such an exemplary application, a free end of a guidewire is percutaneously inserted into a patient's vasculature at a suitable first puncture site. The guidewire is advanced through the vasculature toward a treatment site where the blood vessel is occluded by a thrombus. In one embodiment, the guidewire wire is directed through the thrombus, and is left in the thrombus during treatment to aid in dispersion of the therapeutic compound into the thrombus.
After advancing the guidewire to the treatment site, the catheter 100 is percutaneously inserted into the patient's vasculature through the first puncture site, and is advanced along the guidewire towards the treatment site using conventional over-the-guidewire techniques. The catheter 100 is advanced until the distal end 106 is positioned at or within the occlusion. In a modified embodiment, the distal end 106 comprises one or more radiopaque markers (not shown) to aid in positioning the distal end 106 within the treatment site.
After the catheter is positioned, the guidewire can be withdrawn from the delivery lumen 112. A therapeutic compound source (not shown), such as a syringe with a Luer fitting, is hydraulically connected to the therapeutic compound inlet port 117 and the control box connector 120 is connected to the control box. Thus, a therapeutic compound can be delivered through the delivery lumen 112 and out the distal exit port 114 to the occlusion. One exemplary therapeutic compound appropriate for treating a thrombus is an aqueous solution containing heparin, urokinase, streptokinase, and/or tissue plasminogen activator.
The ultrasound radiating member 124 can be activated to emit ultrasonic energy from the distal end 106 of the catheter 100. As described above, suitable frequencies for the ultrasonic energy 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 about 20 MHz, and in another embodiment the frequency is between about 1 MHz and 3 MHz. In yet another embodiment, the ultrasonic energy has a frequency of about 3 MHz. The therapeutic compound and ultrasonic energy are applied until the thrombus is partially or entirely dissolved. Once the thrombus has been dissolved sufficiently, the catheter 100 is withdrawn from the treatment site.
Methods of manufacture.
The catheters described herein can be manufactured by sequentially positioning the various catheter components onto the catheter assembly. For example, in one method of manufacture, the ultrasound radiating member 124 is positioned around the outer surface of an intermediate portion of an elongate tube. The elongate tube serves as the inner core 110 and defines delivery lumen 112. The first and second wires 126, 128 are then also disposed along the outer surface of the inner core 110 proximal to the ultrasound radiating member 124. The first wire 126 is electrically connected to an inner surface of the ultrasound radiating member 124, and the second wire is electrically connected to an outer surface of the ultrasound radiating member 124, as illustrated in
After the ultrasound radiating member 124 and wires 126, 128 are secured to the inner core 110, an outer sheath 108 is positioned over a portion of the inner core, leaving the ultrasound radiating member 124 uncovered by the outer sheath 108, as illustrated in
Although an exemplary catheter manufacturing technique has been expounded above, other manufacturing techniques can be used, additional components can be included, and the components set forth above can be modified. For example, in certain embodiments, the catheter 100 further comprises a temperature sensor 136 positioned near the ultrasound radiating member 124, as described above. In other embodiments, the outer sheath 108 can be modified to manipulate the flexibility of the catheter 100, such as by including a stiffening component or metallic braiding and/or coiling.
Techniques to reduce buckling or kinking in an ultrasound, drug delivery catheter.
As described above, the ultrasound catheter should have 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. Buckling and kinking can obstruct the delivery lumen and cause excessive friction between the catheter and the blood vessel. In this section, several techniques are described for reducing the likelihood of buckling and kinking of the catheter with a minimal increase in the catheter stiffness by disposing a spirally cut thin polymeric tubing in regions the catheter body susceptible to buckling or kinking. Such regions may in the region of the proximally adjacent the ultrasound element.
In an exemplary embodiment, the inner tubing stiffener member 202 comprises a simple section of tubing that has been spirally cut from its inner surface to its outer surface as shown in
In an exemplary embodiment, the wall thickness of the outer sheath 108 is between approximately 0.005 inches and approximately 0.002 inches. In another embodiment, the wall thickness of the outer sheath 108 is approximately 0.0015 inches. The pitch of the cut in the inner tubing stiffener member 202 can be of any appropriate length. In a modified embodiment, the pitch of the cut in the inner tubing stiffener member 202 is variable, thereby providing a section of varying flexibility.
The outer polymeric layer 204 can comprise any of a wide variety of materials. Such materials include, but are not limited to, Pebax®, PTFE, PEEK, PE, polyurethanes, polyvinyl chloride, LDPE, LLDPE, or mixtures thereof. In an exemplary embodiment, the outer polymeric layer 204 comprises a heat shrinkable tubing of LDPE or LLDPE, having an EVA content of at least 10% EVA. In another embodiment, the EVA content is between approximately 12% and approximately 20%. In another embodiment, the outer polymeric layer thickness is between approximately 0.005 inches and approximately 0.010 inches. In still another embodiment, the outer polymeric layer thickness is approximately 0.003 inches. The aforementioned polymers can be cross-linked by radiation to increase their strength and to promote heat shrinking.
The outer sheath illustrated in
The outer polymeric layer 204 in
The outer sheath illustrated in
In one embodiment, the outer polymeric layer 240 comprises a, heat-shrinkable material such as a polyethylene. Other suitable materials for the outer polymeric layer 240 include polyurethane, polyvinyl chloride, and other softer and more compliant materials. In such embodiments, the outer polymeric layer 240 extends from the proximal end of the catheter to the distal end of the catheter 230.
The embodiment illustrated in
Braided catheter.
As described above, and as illustrated in
As illustrated in
As noted above, the kink-resisting member 320 can comprise a super-elastic alloy such as titanium/nickel materials known as nitinol. Commercial nitinol alloys containing up to about 8% or more of one or more of the members of the iron group of the periodic table are considered to be encompassed within the class of super-elastic nickel/titanium alloys.
In certain embodiments where a super-elastic alloy is used to form the kink-resisting member 320, after a braid has been woven using a plurality of members, a heat treatment is applied to the kink-resisting member. The heat treatment reduces the likelihood that the braid will unravel during subsequent handling or will change in diameter or spacing during that handling. In the heat treatment, the braids are placed on a heat-resistant mandrel, for example by weaving them onto that mandrel, and the mandrel in then placed in an oven at a elevated temperature for a few minutes. In one embodiment, the oven temperature is between approximately 650° F. and approximately 750° F. The heat treatment anneals the material comprising the ribbon and provides it with a reliable shape for subsequent assembly steps. After heat-treatment, the braid retains its shape and its super-elastic properties.
Although the ribbons comprising the kink-resisting member 320 described above comprise a super-elastic alloy material, in other embodiments the ribbons comprise a braid made of a mixture of materials, such as a blend of super-elastic alloy and stainless steel components or of LCPs. Stainless steels and tungsten alloys can also be used. In certain embodiments, particularly in smaller diameter devices, more malleable metals and alloys, such as gold, platinum, palladium, rhodium, and so forth can be used. A platinum alloy with a few percent of tungsten has high opacity to radio frequency energy. Non-metallic ribbons and filaments can also be used; acceptable materials include, but are not limited to, high performance materials such as those made of polyaramids (for example, Kevlar®), LCPs and carbon fibers.
As used herein, the term “woven braid”, in addition to its ordinary meaning, further includes tubular constructions in which the ribbons, wires, or filaments comprising the construction are woven radially in an in-and-out fashion as they cross each other to form a tubular member having a single lumen. For example, the braid shown in
In certain embodiments wherein the innermost layer 322 comprises a fluorinated polymer, the outside surface of the innermost layer 322 can be etched to provide a good mechanical surface to which adjacent polymers will readily adhere. Certain procedures using, for example, treatment with a mixture of aliphatic hydrocarbons and sodium metal as the etching solution is effective in such service.
The kink-resisting member 320 can be placed directly adjacent innermost layer 322. In modified embodiments, kink-resisting member 320 is radially encased by one or more layers, such as an inner filler layer 326 and an outer filler layer 328. In such modified embodiments, the likelihood of slip or shift of the kink-resisting member 320 against the typically lubricious innermost layer 322 can be reduced. The filler layers 126, 128 adhere to the kink-resisting member 320 and form a determinate layer that enhances the kink-resisting capabilities of the catheter distal end 106. To soften the outer surface of the distal end 106 and to lower the stiffness of the distal end 106, a distal outer shaft layer 330 is placed on the outside surface of the filler layers 126, 128. In certain embodiments, the distal outer shaft layer 330 extends for substantially the entire length of the catheter distal end 106. The filler layers 126, 128 can be configured as extensions of tapered components of the assembly joint found in the junction section 306, discussed in greater detail below. Distal most sections made in this way can undergo bends of 1/32 inch diameter without visible kinking.
In an exemplary embodiment, the filler layers 326, 328 are similar materials. In one embodiment, the filler layers 326, 328 have a Shore hardness of approximately 45 D to approximately 60 D. In another embodiment, the filler layers 326, 328 have a Shore hardness of approximately 55 D. In one embodiment, the distal outer shaft layer 330 is a second material having a Shore hardness of between approximately 70 A and approximately 85 A. In another embodiment, the distal outer shaft layer 330 has a Shore hardness of approximately 75 A. The filler layers 326, 328 and the distal outer shaft layer 330 can comprise a variety of materials. In one embodiment, the filler layers 326, 328 and the distal outer shaft layer 330 comprise polymeric and selected other materials that tend to tack to each other upon heating. Such materials can also be melt-miscible. In other embodiments, the filler layers 326, 328 and the distal outer shaft layer 330 contain ancillary components that act as adhesives. The materials comprising the filler layers 326, 328 and the distal outer shaft layer 330 can be made of heat-shrinkable materials (for example, irradiated low-density polyethylene), or such materials can be otherwise placed onto the structure of the filler layers 326, 328 and the distal outer shaft layer 330. Examples of such materials include polyurethanes and their alloys, mixtures, and co-polymers. In certain embodiments, the filler layers 326, 328 and the distal outer shaft layer 330 comprise polymeric materials such as polyethylene, polypropylene, PVC, EVA, polyurethanes, polyamides, PET, and their mixtures and co-polymers. In other embodiments, the filler layers 326, 328 and the distal outer shaft layer 330 comprise mixtures of polyurethanes and polycarbonates sold as “Carbothane”.
As described above, the junction section 306 is located proximal to the distal end 106. The junction region 306 includes the region proximal to the distal end 106 that contains any tubing joint which has a tapering surface.
In an exemplary embodiment, and as illustrated in
In certain embodiments, multiple polymeric layers are included in the junction section 306 and the catheter distal end 106. In other embodiments, at least one of the exterior and interior surfaces of the catheter are coated with a lubricious layer that is either chemically bonded to the surface or physically coated to the relevant catheter exterior surface. Exemplary procedures for producing bonded lubricious coatings are described U.S. Pat. Nos. 5,531,715 and 5,538,512.
The polymers noted herein can be filled with radiopaque materials such as barium sulfate, bismuth trioxide, bismuth carbonate, powdered tungsten, powdered tantalum and so forth. In such embodiments, the location of the various portions of the catheter can be radiographically visualized in the human body.
In other embodiments, the pitch of kink-resisting member 320 varies within the catheter distal end 106. In one such embodiment, the pitch of kink-resisting member 320 is greater towards the catheter distal end 106, thereby providing enhanced flexibility in that region.
The components described herein that have tapering surfaces can be manufactured by placing an appropriately sized tubing section on a mandrel having the sought shape. The tubing section is then stretched until the sought shape is achieved. The tubing section is then removed from the mandrel and is cut to the appropriate size.
In an exemplary catheter assembly technique, the lubricious innermost layer 322 is placed on a mandrel and axially stretched to produce axial molecular orientation. In an exemplary embodiment, the mandrel chosen provides an appropriate change in the innermost layer 322 inner diameter, as described above. The catheter elements are then assembled as illustrated in
Techniques for producing variable flexibility.
As described above, providing a ultrasound catheter with a variable flexibility can enhance maneuverability of the catheter through small vessels of a patient's vasculature. In particular, in certain embodiments a proximal region of the catheter has decreased flexibility to enhance pushability, torqueability and kink-resistance, while a distal region of the catheter has increased flexibility to allow the catheter to easily track a guidewire and to navigate small-radius bends of a patient's vasculature. Often, the distal end of an ultrasound catheter will have decreased flexibility in the region of the ultrasound radiating member.
In the exemplary embodiment illustrated in
The exemplary embodiment illustrated in
The diameter of the delivery lumen 112, x, can vary depending on several factors, including the size of the guidewire to be used with the catheter. In
In an exemplary embodiment, both the tubular body 108 and the stiffener strands 150 comprise polymers, including thermoplastics such as LDPE, HDPE, polypropylene, polystyrene, polyurethanes, polyesters (including nylon), polyfluorocarbons, and polyolefin. In other embodiments, the tubular body 108 and the stiffener strands 150 comprise composite materials, blends, and copolymers of the aforementioned compounds. For example, in one embodiment, the stiffener strands 150 comprise a material having a stiffness greater that the stiffness of the outer sheath 108. In such embodiments, the two materials can be miscible, such that the stiffener strands 150 will melt into the outer sheath 108 when extruded, and will form a catheter body without distinct boundaries between the stiffener strands 150 and the outer sheath 108.
In one exemplary embodiment, the catheter comprises an outer sheath 108 made of LDPE and polyolefin (ethylene octane) in approximately equal portions, and stiffener strands 150 made of a higher stiffness material, such as HDPE. The materials comprising the catheter can vary according to the intended use, and many other plastics and composite materials, and even metals, can be used. For example, in one embodiment, the outer sheath 108 comprises LDPE, and the stiffener strands 150 comprise HDPE, LDPE, or a mixture of the two.
In a modified embodiment, the relative stiffness of the materials comprising the outer sheath 108 and the stiffener strands 150 is reversed, with the outer sheath 108 comprising the stiffer material, and the stiffener strands 150 comprising the more flexible material. In such embodiments, the stiffener strands 150 will be thicker at the catheter distal end 106 and thinner at the catheter proximal end 104, thereby providing the catheter with increasing flexibility distally.
In modified embodiments, the catheters described herein can further include one or more radiopaque markers to assist in positioning the catheter in, and navigating the catheter through, a patient's vasculature.
The catheters described herein can be used in the highly tortuous blood vessels of the body, including the coronary blood vessels, renal blood vessels, and intracranial blood vessels. As used herein, the term “highly tortuous” refers, in addition to its ordinary meaning, to the tortuosity typically encountered in the vascular pathway from a remote access site such as the femoral artery to target sites deep within the coronary, renal sinus and cerebral vasculature. Specific catheter embodiments can be constructed for access into targeted sites involving pathologically tortuous blood vessels. As used herein, the term “pathological tortuosity” refers, in addition to its ordinary meaning, to the vascular pathway from a remote access site such as the femoral artery to target sites involving (a) turns in excess of 90°, such as encountered when branching from one blood vessel to another blood vessel (that is, paths that branch off the preceding vessel at angles greater that a right angle), and (b) a total path length within the target tissue at least approximately 5 cm. Pathological tortuosity includes treatment sites accessible by a guidewire approximately 0.018 inches or smaller.
The variable flexibility catheters described herein can be used with a guidewire, although a guidewire is not required. The catheter flexibility can be varied to allow the catheter to be guided to the treatment site in a flow directed manner, or through manual steering. The materials and dimensions described herein can be varied so that the catheter can be used in highly tortuous pathways with or without a guidewire. The variable flexibility catheters described herein can increase catheter maneuverability despite the presence of a relatively rigid ultrasound radiating member at the distal end of the catheter.
The variable flexibility catheters described herein can be manufactured using various known extrusion methods. Known methods of co-extrusion, including for example cross header arrangements, over-extrusion, and extrusion die construction can be applied to manufacture these catheters. Stiffener strand thickness, wall thickness, and relative percentage of outer sheath composition can be controlled with known techniques including for example speed controlled extrusion, throttled flow controlled extrusion, and waste-gating. The materials disclosed herein can be used in catheter fabrication, but it is expected that new and improved materials will also be applied in the construction of the catheters disclosed herein.
For example, in one exemplary method of manufacture, a catheter is manufactured by an extrusion method in which the tubular catheter having a plurality of stiffener strands is co-extruded from a first material forming the outer sheath 108, and a second material forming the stiffener strands 150. The diameter of the stiffener strands 150 can be varied during the extrusion process to form a catheter having a changing flexibility along its length.
In another exemplary method of manufacture, the catheter is extruded as a tubular member having a substantially constant cross-sectional configuration that includes a first outer sheath material and a second stiffener strand material. The extruded tubular member having a substantially constant cross-sectional configuration is then heated and stretched to a final configuration in which the catheter distal end is smaller in diameter and more flexible than the catheter proximal end. The cross sections of a distal, intermediate, and proximal portion of a catheter formed by this method are illustrated in
Multi-Segment Catheter.
As described above, providing a ultrasound catheter with a variable flexibility can enhance maneuverability of the catheter through small vessels of a patient's vasculature. In particular, in certain embodiments a proximal region of the catheter has decreased flexibility to enhance pushability, torqueability and kink-resistance, while a distal region of the catheter has increased flexibility to allow the catheter to easily track a guidewire and to navigate small-radius bends of a patient's vasculature. Often, the distal end of an ultrasound catheter will have decreased flexibility in the region of the ultrasound radiating member.
The outer tube 918 extends over substantially the entire length of the catheter, which can be over approximately 50 cm, and is between approximately 80 cm and approximately 150 cm in certain embodiments. (As described above, in certain embodiments the outer tube 918 does not cover an ultrasound radiating member positioned at the catheter distal end.) The outer diameter of outer tube 918 (as measured at the catheter proximal end) can be between approximately 0.75 mm and 2.00 mm, and is between approximately 0.85 mm and 1.30 mm in certain embodiments. In a modified embodiment, the outer tube 918 necks down at its distal end, such that its outer diameter at the distal end is slightly smaller than at its proximal end. The outer tube 918 can have a wall thickness of between approximately 0.08 mm and approximately 0.16 mm, and has a wall thickness of between approximately 0.10 mm and approximately 0.13 mm in certain embodiments. In an exemplary embodiment, the outer tube 918 comprises a polymer having a flexural modulus (as measured by ASTM D-790) of between approximately 100,000 kPa and approximately 250,000 kPa, such as low density polyethylene.
In the exemplary embodiment illustrated in
Referring still to the exemplary embodiment illustrated in
The distal inner tubular segment 921 extends from intermediate junction 923 to a location 924 proximal to the distal end of the catheter. For example, in one embodiment, location 924 can be adjacent the proximal end of an ultrasound radiating member. In one embodiment the length of the distal inner tubular segment 921 is between approximately 5 cm and approximately 20 cm, in another embodiment the length of the distal inner tubular segment 921 is between approximately 7 cm and approximately 15 cm, and in yet another embodiment, the length of the distal inner tubular segment 921 is approximately 10 cm.
Based on the foregoing, in an exemplary embodiment, the distance from proximal junction 922 to the distal end of the catheter will be greater than approximately 50% of the entire length of catheter. In another embodiment, the distance from proximal junction 922 to the distal end of the catheter will be greater than approximately 60% of the entire catheter length. In such embodiments, distal inner tubular segment 921 is less stiff than intermediate inner tubular segment 920, and provides a transition in flexibility between inner tubular segment 920 and the portion of the outer tube 918 that extends distal to location 924. In such embodiments, the wall thickness of distal inner tubular segment 921 (a) is less than that of intermediate inner tubular segment 920, and/or (b) comprises a polymer having a lower flexural modulus than the polymer comprising intermediate inner tubular segment 920. For example, in one embodiment, distal inner tubular segment 921 comprises a polymer having a flexural modulus that is (a) significantly lower than the polymer comprising intermediate inner tubular segment 920 but (b) higher than the polymer comprising the outer tube 918. The distal inner tubular segment 921, for instance, can be linear, low density polyethylene. Typically, the flexural modulus of the polymer comprising distal inner tubular segment 921 is between approximately 150,000 kPa and approximately 350,000 kPa. In one embodiment, , the flexural modulus of the polymer comprising distal inner tubular segment 921 is between approximately 200,000 kPa and approximately 300,000 kPa. In one embodiment the wall thickness of distal inner tubular segment 921 is between approximately 0.05 mm and 0.10 mm, and in another embodiment the wall thickness of distal inner tubular segment 921 is between approximately 0.06 mm and 0.09 mm. In an exemplary embodiment, the inner diameters of segments 920, 921 are substantially the same as that of segment 919.
Although junctions 922, 923 are illustrated as butt joints in
Thus, the catheter illustrated in
Proximal element joint.
Several techniques for varying the flexibility, stiffness and other mechanical properties of a catheter body are disclosed herein. As described elsewhere in this specification, in certain embodiments the catheter body is less flexible at the catheter proximal end, and gradually increases in flexibility toward the distal end. This configuration advantageously enhances catheter maneuverability by facilitating the pushing, twisting or other motions used when advancing the catheter over a guidewire and through a patient's vasculature to a treatment site. For example, a catheter with increasing distal flexibility often has enhanced kink resistance.
However, as described above, many of the techniques for manipulating the mechanical properties of the catheters described herein can be used with a catheter having one or more ultrasound radiating members mounted in a catheter distal region. In such embodiments, the ultrasound radiating member acts as a relatively stiff tip in the end region of an otherwise flexible catheter. Thus, at the proximal element joint there is a discontinuous change in flexibility from the relatively flexibility distal region of the outer sheath to the relatively rigid ultrasound radiating member. As described previously, reducing the rigidity of the proximal element joint enhances the joint flexibility, reduces the likelihood of kinking in the catheter flexible support section, and facilitates tracking of the catheter over the guidewire.
Thus, in an exemplary embodiment, any of the techniques described herein from introducing a gradually increasing flexibility from the catheter proximal region to the catheter distal region can also be used to introduce a variable flexibility at the proximal element joint. For example, the flexibility of the outer sheath can gradually decrease in a region proximal to the ultrasound radiating member, thereby eliminating the discontinuous change in flexibility at the proximal element joint.
The relative catheter flexibility as a function of axial catheter position of such an exemplary embodiment is illustrated in
Likewise, in the proximal element joint region 162, where the catheter is becoming less flexible distally, any of the methods described herein for providing variable catheter flexibility can be used. Such methods include, but are not limited to, use of braids, compression regions, stiffener wires, and composite materials. Such methods can be employed to eliminate a discontinuous change in catheter flexibility at the proximal element joint between the catheter distal region and the relatively rigid ultrasound radiating member region 164.
Still referring to
With continued reference to
Delivery lumen with composite tubing.
As described above, if the ultrasound catheter buckles or kinks during advancement through the patient's vasculature, it may not be possible to deliver the ultrasound radiating member to the treatment site. With respect to the neurovascular system, this is an important technical hurdle that has limited the use of ultrasound catheters. Furthermore, buckling or kinking of the catheter can damage the patient's vasculature.
With respect to the ultrasound catheter described above, it is particularly advantageous that the inner core 110 does not undergo kinking or distortion (also referred to as “ovalization”) when the catheter is passed through difficult regions of the patient's vasculature. Such ovalization will cause the inner core 110 to bind on the guidewire over which the catheter is advanced. Thus,
As shown in
In the illustrated embodiment, the outer member 1209 preferably comprises a lubricious polymer that can be coated with a layer of an additional material . In the preferred embodiment, the outer member comprise a Pebax® wall 1208 that is coated with a Tecoflex® outer skin 1210. Of course, other materials can be used in other embodiments.
In one embodiment, the inner member 1204 comprises a 0.005 inch thick Teflon layer. The reinforcing member 1206 comprises a 0.0005 inch thick flat wire stainless steel wire coil, wrapped around the Teflon layer. A Pebax layer is overlayed over the wire coil and Teflon layer. The Pebax layer has a thickness of about 0.00075 inches over the wire and about 0.00125 inches over the gaps in the wire. A layer of Tecoflex having a thickness of about 0.00025 is preferably provided over the Pebax layer.
As mentioned above, in the preferred embodiment, the inner core 1202 is configured such that at least a portion of the reinforcing member 1206 can flex with respect to the longitudinal axis of the catheter. In between freely flexing portions, the reinforcing member 1206 may be fixed with respect to the inner member 1204 and/or outer member 1209. In one preferred embodiment, the reinforcing member 1206 may be fixed with respect to the inner member 1204 and/or outer member 1209 only at the distal and proximal portions or ends of the inner core 1202.
In one embodiment, the reinforcing member 1206 extends over at least about 50% of the length of the catheter. In another embodiment, the reinforcing member 1206 extends over at least about 75% of the length of the catheter. In another embodiment, the reinforcing member 1206 extends over substantially the entire length of the catheter. These arrangements advantageously allow the reinforcing member to flex as the catheter is advanced through torturous anatomy, while still reducing ovalization.
As mentioned above, guidewire movement can be hindered by kinking or distortion (also referred to as “ovalization”) of the catheter body. Kink resistance of the ultrasound catheter, which is also related to the ability to freely pass a guidewire through the catheter, can be evaluated by testing the minimum radius 180° bend that the catheter can be subjected to without kinking. In an exemplary embodiment, the catheter with the composite inner core 1202 described above can be subjected to a 180° bend having a radius of less than about 10 mm without kinking. In another exemplary embodiment, the catheter can be subjected to a about 180° bend having a radius of less than about 8 mm without kinking. In still another exemplary embodiment, the catheter can be subject to a 180° bend having a radius of less than or equal to about 6 mm without kinking. In such embodiments, the inner core 1202 is configured to receive a standard 0.014 inch guidewire, which may be up to about 0.017 inches in diameter. In one embodiment, the inner diameter of the inner member 1204 is approximately 0.018 inches±0.005 inches. In other embodiments, the inner diameter of the internal liner 1204 is approximately 0.018 inches±0.010 inches. In still other embodiments, the inner diameter of the internal liner 1204 is approximately 0.018 inches±0.100 inches.
In embodiments wherein the ultrasound catheter includes the composite delivery lumen 1202 described herein, the kink resistance and flexibility of the catheter 100 is advantageously increased, as compared to a catheter with a delivery lumen consisting solely of polyimide. This configuration also reduces the tendency of the tubular body to become ovular when passed through difficult regions of the patient's vasculature, thereby reducing the likelihood of binding of the guidewire within the delivery lumen 1202. Additionally, the presence of the reinforcing member 1206 increases the burst strength, kink resistance and flexibility of the delivery lumen 1202, and provides for a stronger bond at locations where other catheter components are to be bonded to the delivery lumen 1202—such as at the distal and proximal ends of the delivery lumen 1202. It should also be appreciated that the reinforcing member 1206 may be used to control the flexibility of the delivery lumen 1202 and, in turn, the catheter. This may be done by varying the thickness and/or properties of the reinforcing member 1206.
In certain embodiments, the delivery lumen can be configured with dimensions to increase the size of the region 138 (see
The techniques for increasing the maneuverability of the tubular body described herein can be applied to the entire length of the tubular body, or can be applied to a portion of the tubular body. In other embodiments, the techniques can be applied along different lengths of the catheter to varying degrees. For example, in one such embodiment, the tubular body can be configured with a varying flexibility, such that the flexibility of the tubular body gradually increases from the proximal region to the distal region as described above. Also as described above, other characteristics of the tubular body, such as kink resistance and torqueability, can be can be varied along the length of the catheter.
In embodiments wherein the delivery lumen comprises a composite delivery lumen 1202 as described above, and as illustrated in
For example, the backend hub 118 illustrated in
The other end of the polyimide sleeve 1212 is engaged with a Luer fitting 1214 in the backend hub 118 to anchor the polyimide sleeve 1212 in place. In an exemplary embodiment, the length of engagement between the polyimide sleeve 1212 and the Luer fitting 1214 is approximately 0.400 inches, although other dimensions can be used in other embodiments.
In embodiments wherein the delivery lumen comprises a composite delivery lumen 1202, a polyimide tube 1216 can be bonded to the distal end of the composite delivery lumen 1202, as illustrated in
Still referring to the exemplary embodiment illustrated in
The configuration of the distal delivery lumen bond 1218 described herein advantageously provides a secure, slip-fit joint between the composite delivery lumen 1202 and the polyimide tube 1216. The distal delivery lumen bond 1218 has a relatively smooth transition along the inner diameter. Heat can be used to bond and seal the joint; no adhesive is necessary, although an adhesive can be used in a modified embodiment. Using heat to bond the joint advantageously provides a high bond strength, allows close control of any reflow of the delivery lumen inner diameter, and provides a relatively small, low profile bond. However, other bonding techniques can be used in other embodiments.
The distal delivery lumen bond 1218 configuration described herein advantageously facilitates passage of a guidewire through the distal delivery lumen bond 1218, and generally improves the flexibility of the proximal element joint, thereby enhancing catheter accessibility to the distal vasculature. This configuration also covers sharp ends which can be present at the distal end of the composite delivery lumen 1202, such as from the coil 1206.
Furthermore, the presence of the distal delivery lumen bond 1218 in region 138 between the composite delivery lumen 1202 and the outer sheath 108 creates a narrow passage 1220 which can be used to hold an electrical conductor (not shown) in place, such as the electrical conductors used to drive the ultrasound radiating member. This configuration can reduce the likelihood of accidental disconnection of the electrical conductor from the ultrasound radiating member.
In a modified embodiment, the catheter can be etched in the region of the distal delivery lumen bond 1218. The etching generally increases the strength of the distal delivery lumen bond 1218.
With continued reference to
Potting material may be placed between the ultrasound radiating member 124 and the sleeve 130 and/or polyimide tube 1216. The potting material reduces movement between these members and provides electrical insulation.
As described above, in the embodiment illustrated in
As described with the embodiment of
In a preferred embodiment, the portions of the conductive wires 126, 128 and/or the control wire 127 positioned between the outer and inner components of the catheter has an extended length that is longer than the extended length of the corresponding outer and inner components of the catheter. In this manner, the wires 126, 127, 128 have slack such that, as the catheter is advanced through the vascular system, the wires 126, 127, 128 do not substantially add to the stiffness of the catheter. In addition, because the wires 126, 127, 128 can freely move they can bend and compress further reducing the stiffness of the catheter. In one embodiment, the portions of the conductive wires 126, 128 and/or the control wire 127 positioned between the outer and inner components of the catheter has an extended length that is in the range of about 0.02% longer than the extended length of the corresponding outer and inner components of the catheter. In another embodiment, the extend length is at least about 0.5% longer, and in another embodiment at least about 0.70% longer. In one embodiment, the extend length is in the range of about 0.02% to about 0.70% longer than the extended length of the corresponding outer and inner components of the catheter and in another embodiment, the extended length is in the range of about 0.02% to about 0.50% longer. In these embodiments, the wires 126, 127, 128 may be wrapped (e.g., helically wrapped) about the inner core 1202 to take up the extra length.
Ultrasound catheter with reduced distal rigid section.
As described previously, the ultrasound catheter often has a region of decreased flexibility in the distal region of the catheter around the ultrasound radiating member (see, for example, ultrasound radiating member region 164 in
The ability of the ultrasound catheter to reliably track the guidewire can be improved by decreasing the length of the distal tip region 166. For example, in one embodiment of an ultrasound catheter with improved guidewire tracking performance, the length of the distal tip region 166 is between approximately 0.35 inches and approximately 0.45 inches. Indeed, implementation of design improvements such as this allow the length of the ultrasound radiating member 124 to be increased—thereby advantageously allowing more ultrasonic energy to be delivered to the treatment site—without adversely affecting the ability of the ultrasound catheter to reliably track the guidewire in distal regions of the patient's vasculature. Furthermore, decreasing the length of the distal tip region 166 advantageously reduces the tendency of the distal exit port 114 to open and become folded back on itself (commonly referred to as “fishmouthing”) as the catheter is passed through the patient's vasculature.
Other aspects of the ultrasound catheter distal tip design can be manipulated to reduce the length of the distal rigid section, and therefore to enhance the maneuverability of the ultrasound catheter. For example, the ability of the ultrasound catheter to reliably track the guidewire can be improved by reducing the wicking of adhesive 132 (see
Benchmarking.
Ultrasound catheters manufactured according to the various embodiments provided herein and, in particular, the improvements described with reference to
For example, the stiffness of the catheter as a function of axial catheter position can be determined using an Instron® tensile strength testing machine. In one exemplary embodiment, the stiffness of the ultrasound catheter is less than about 0.05 pounds in a region within 20 cm from the distal catheter tip. In another exemplary embodiment, the stiffness of the ultrasound catheter is less than about 0.15 pounds in a region within 20 cm from the distal tip. In another exemplary embodiment, the stiffness of the ultrasound catheter is less than about 0.10 pounds in a region within 30 cm from the distal tip. In another exemplary embodiment, the stiffness of the ultrasound catheter is less than about 0.20 pounds in a region within 30 cm from the distal tip.
Guidewire movement, which can be hindered by kinking or distortion (also referred to as “ovalization”) of the catheter body, can be determined by observing guidewire movement through loops and/or curves of varying diameter. For example, in one test, a standard 0.014 inch guidewire is passed through a catheter bent into one or more 360° loops having diameters of between about 6 mm and about 12 mm. Such loops are representative of the tortuosity encountered in accessing a typical treatment site, such as the middle cerebral artery. In another test, the catheter is bent into a series of S-curves. As the guidewire is pushed and pulled through the loop/curve, any drag, bumps or wire flexure is observed, which may indicate a kink in the catheter, ovalization of the catheter, binding of the guidewire, or some other deleterious condition.
The ability of the ultrasound catheter to track the guidewire at a difficult region of the patient's vasculature, such as at a small radius bend or at a bifurcation, can also be evaluated. Generally, a greater force is required to navigate the catheter around a small-radius curved path than a large-radius curved path; and generally a greater force is required to navigate the ultrasound catheter around a 180° curve than a curve less than 180°. For example, in one embodiment, less than approximately 10 grams are required to pull an ultrasound catheter over a standard 0.014 inch guidewire around a 7 mm diameter curve. In another embodiment, less than approximately 8 grams are required to pull an ultrasound catheter over a standard 0.014 inch guidewire around a 7 mm diameter curve.
These improvements allow the ultrasound catheter disclosed herein to consistently and safely reach the distal regions of a patient's neurovascular system, including, but not limited to, the main and subsequent branches of the middle cerebral artery. This represents a significant advancement in ultrasound catheters.
In addition to the flexibility improvements described above, it is also advantageous that the flexibility characteristics described above are achieved with an ultrasound catheter that provides enough room for a transducer element of sufficient size to deliver a therapeutically sufficient dose of ultrasound energy. Accordingly, in one embodiment, the ultrasound catheter has a utility lumen inner diameter of less than about 0.018 inches, and in another embodiment, less than about 0.017 inches and yet still capable of being able to receive a standard 0.014 inch guidewire. In such an embodiment, the outer diameter of the region of the catheter comprising the ultrasound radiating member, has a diameter of greater than about 2.0 French, and in another embodiment, a diameter that is greater than about 2.8 French, and in another embodiment greater than about 3.3 French. This arrangement advantageously allows a sufficiently large transducer element to advanced through small blood vessels, such as the main and subsequent branches of the middle cerebral artery.
Conclusion.
While the foregoing detailed description has set forth several exemplary embodiments of the apparatus and methods of the present invention, it should 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 disclosed can differ from those described above, and that the methods described can be used within any biological conduit within the body.
This application claims the benefit of U.S. Provisional Application 60/539,954 (filed 29 Jan. 2004; Attorney Docket EKOS.168PR) and U.S. Provisional Application 60/570,969 (filed 14 May 2004; Attorney Docket EKOS.168PR3). All of these priority applications are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60539954 | Jan 2004 | US | |
| 60570969 | May 2004 | US |
