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WO2002005863A1 - Stent radio-opaque en alliage binaire - Google Patents

Stent radio-opaque en alliage binaire Download PDF

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Publication number
WO2002005863A1
WO2002005863A1 PCT/US2001/020512 US0120512W WO0205863A1 WO 2002005863 A1 WO2002005863 A1 WO 2002005863A1 US 0120512 W US0120512 W US 0120512W WO 0205863 A1 WO0205863 A1 WO 0205863A1
Authority
WO
WIPO (PCT)
Prior art keywords
stent
alloy
tantalum
percentage
cylindrical
Prior art date
Application number
PCT/US2001/020512
Other languages
English (en)
Inventor
Stephen D. Pacetti
Original Assignee
Advanced Cardiovascular Systems, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Advanced Cardiovascular Systems, Inc. filed Critical Advanced Cardiovascular Systems, Inc.
Priority to JP2002511794A priority Critical patent/JP2004503334A/ja
Priority to EP01948783A priority patent/EP1301224A1/fr
Priority to AU2001270216A priority patent/AU2001270216A1/en
Publication of WO2002005863A1 publication Critical patent/WO2002005863A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/82—Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/86—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
    • A61F2/90—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure
    • A61F2/91—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheets or tubes, e.g. perforated by laser cuts or etched holes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/82—Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/86—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
    • A61F2/90—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure
    • A61F2/91—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheets or tubes, e.g. perforated by laser cuts or etched holes
    • A61F2/915—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheets or tubes, e.g. perforated by laser cuts or etched holes with bands having a meander structure, adjacent bands being connected to each other
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L31/00—Materials for other surgical articles, e.g. stents, stent-grafts, shunts, surgical drapes, guide wires, materials for adhesion prevention, occluding devices, surgical gloves, tissue fixation devices
    • A61L31/02—Inorganic materials
    • A61L31/022—Metals or alloys
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L31/00—Materials for other surgical articles, e.g. stents, stent-grafts, shunts, surgical drapes, guide wires, materials for adhesion prevention, occluding devices, surgical gloves, tissue fixation devices
    • A61L31/14—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
    • A61L31/18—Materials at least partially X-ray or laser opaque
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
    • C22C27/02—Alloys based on vanadium, niobium, or tantalum
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/82—Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/86—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
    • A61F2/90—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure
    • A61F2/91—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheets or tubes, e.g. perforated by laser cuts or etched holes
    • A61F2/915—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheets or tubes, e.g. perforated by laser cuts or etched holes with bands having a meander structure, adjacent bands being connected to each other
    • A61F2002/91533—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheets or tubes, e.g. perforated by laser cuts or etched holes with bands having a meander structure, adjacent bands being connected to each other characterised by the phase between adjacent bands
    • A61F2002/91541—Adjacent bands are arranged out of phase
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2230/00—Geometry of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2230/0002—Two-dimensional shapes, e.g. cross-sections
    • A61F2230/0004—Rounded shapes, e.g. with rounded corners
    • A61F2230/0013—Horseshoe-shaped, e.g. crescent-shaped, C-shaped, U-shaped
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2230/00—Geometry of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2230/0002—Two-dimensional shapes, e.g. cross-sections
    • A61F2230/0028—Shapes in the form of latin or greek characters
    • A61F2230/0054—V-shaped
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2250/00—Special features of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2250/0058—Additional features; Implant or prostheses properties not otherwise provided for
    • A61F2250/0096—Markers and sensors for detecting a position or changes of a position of an implant, e.g. RF sensors, ultrasound markers
    • A61F2250/0098—Markers and sensors for detecting a position or changes of a position of an implant, e.g. RF sensors, ultrasound markers radio-opaque, e.g. radio-opaque markers

Definitions

  • the present invention relates generally to endoprosthesis devices, which are commonly referred to as stents, and more particularly to radiopaque stents.
  • Stents are generally thin walled tubular-shaped devices composed of complex patterns of interconnecting struts which function to hold open a segment of a blood vessel or other body lumen such as a coronary artery. They also are suitable for supporting a dissected arterial lining or intimal flap that can occlude a vessel lumen.
  • stents being marketed throughout the world. These devices are typically implanted by use of a catheter which is inserted at an easily accessible location and then advanced through the vasculature to the deployment site. The stent is initially maintained in a radially compressed or collapsed state to enable it to be maneuvered through the lumen. Once in position, the stent is deployed.
  • deployment is achieved by the removal of a restraint, such as the retraction of a delivery sheath.
  • a restraint such as the retraction of a delivery sheath.
  • deployment is achieved by inflation of a dilation balloon about which the stent is earned on a stent-delivery catheter.
  • the stent must be able to simultaneously satisfy a number of mechanical requirements.
  • the stent must be capable of withstanding the structural loads, namely radial compressive forces, imposed on the stent as it supports the walls of a vessel lumen.
  • the stent should be longitudinally flexible to allow it to be maneuvered through a tortuous vascular path and to enable it to conform to a deployment site that may not be linear or may be subject to flexure.
  • the material from which the stent is constructed must allow the stent to undergo expansion which typically requires substantial deformation of localized portions of the stent's structure.
  • the stent Once expanded, the stent must maintain its size and shape throughout its service life despite the various forces that may come to bear thereon, including the cyclic loading induced by the beating heart. Finally, the stent must be biocompatible so as not to trigger any adverse vascular responses.
  • a stent should also be radiopaque or fluoroscopically visible.
  • Accurate stent placement requires real time visualization to allow the vascular surgeon to track the delivery catheter through the patient's vasculature and precisely place the stent at the site of a lesion. This is typically accomplished by fluoroscopy or similar x-ray visualization procedures.
  • For a stent to be fluoroscopically visible it must be more absorptive of x- rays than the surrounding tissue. This is typically accomplished by the use of radiopaque materials in the construction of a stent, which allows for its direct visualization.
  • the most common materials used to fabricate stents are stainless steel and nickel-titanium alloys, neither of which is particularly radiopaque. This factor, in combination with the relatively thin wall thickness (about 0.002 to 0.006 inch) of most stent patterns renders stents produced from these materials insufficiently radiopaque to be adequately visualized with fluoroscopy procedures. Although both materials are generally regarded as being bio-compatible, some recent concerns have arisen regarding the biocompatibility of stainless steel. Over time, nickel, a constituent element of most stainless steels, tends to leach from a stainless steel stent and in some sensitive patients will produce an allergic reaction. In addition, the chromium oxide layer present on the surface of stainless steel stents to prevent corrosion may have a tendency to degrade during long term use within the body.
  • non-toxic, high density metals such as tantalum, iridium, platinum, gold, and the like
  • these alloys are either excessively radiopaque or may lack sufficient strength for recoil, radial strength requirements, and long-term use in a dynamic vascular setting.
  • Stents constructed of highly radiopaque materials appear overly bright when viewed under a fluoroscope. This tends to overwhelm the image of the tissue surrounding the stent and obscures visualization of the stent lumen. Due to the lack of an appropriately radiopaque material, simply constructing a stent wholly out of a single material has heretofore not resulted in a stent with the optimal combination of mechanical properties and radiopacity.
  • radiopaque markers One means frequently described for increasing fluoroscopic visibility is the physical attachment of radiopaque markers to the stent.
  • Conventional radiopaque markers have a number of limitations. Upon attachment to a stent, such markers may proj ect from the surface of the stent, thereby comprising a departure from the ideal profile of the stent. Depending on their specific location, the marker may either proj ect inwardly to disrupt blood flow or outwardly to traumatize the walls of the blood vessel. Additionally, galvanic corrosion may result from the contact of two disparate metals, i.e., the metal used in the construction of the stent and the radiopaque metal of the marker.
  • Discrete stent markers cannot show the entire outline of the stent which is a preferred method to determine the optimal expansion of a stent over its entire length.
  • the radiopacity of stents has also been increased by plating or coating selected portions thereof with radiopaque material.
  • a number of disadvantages are associated with this approach as well. When the stent is expanded certain portions undergo substantial deformation, creating a risk that cracks may form in the plating or coating causing portions of the plating to separate from the underlying substrate.
  • composite stents whether equipped with markers or radiopaque plating, have several disadvantages; namely, separation of the markers, plating, or coating from the substrate material, which may allow the metallic particles to flow downstream within a vessel lumen causing potential blockages or other adverse effects upon the patient.
  • a stent that overcomes the shortcomings inherent in previously known devices.
  • a stent would be formed from a single material, possess the required mechanical characteristics, and also be sufficiently radiopaque to be readily visible using fluoroscopy procedures.
  • the present invention provides a stent made from a binary alloy of either tantalum-tungsten or tantalum-niobium that overcomes the shortcomings of previously known stent devices.
  • the stent fulfills all of the mechanical and structural requirements attendant to its function as a stent.
  • the stent is sufficiently radiopaque to allow for good imaging of the stent under fluoroscopy without the addition of an extra layer of radiopaque material.
  • the stent is not overly bright and therefore does not obscure the image of the surrounding vessel lumen into which the stent is placed, as would be the case with a stent made from pure tantalum.
  • the stent of the present invention achieves its results by utilizing the heretofore unappreciated properties of tantalum-tungsten and tantalum-niobium alloys.
  • Tantalum-tungsten alloys have approximately the same radiopacity as pure tantalum, however, the alloys are substantially stronger than pure tantalum and in some compositions are also stronger than stainless steel.
  • the alloy ' s strength allows for a stent to be produced with a wall thickness comparatively thinner than that of a stent produced from pure tantalum. Since radiopacity is function of material density, and of the stent's wall or strut thickness, it is possible to tailor the thickness of tantalum-tungsten stents to produce a stent with a radiopacity less than that of a pure tantalum stent, yet greater than that of a conventional stainless steel stent.
  • Tantalum-niobium alloys with a high percentage of niobium (about 40%) are stronger than pure tantalum and, more importantly, are substantially less dense than pure tantalum as niobium has an atomic mass of approximately one half that of tantalum.
  • the thickness of a tantalum-niobium alloy stent may also be tailored to achieve a radiopacity between that of a pure tantalum stent and a conventional stainless steel stent.
  • the stent of the present invention may have virtually any configuration that is compatible with, and maintains the patency of, the body lumen in which it is implanted.
  • stents are composed of an intricate geometric pattern of cylindrical rings and connecting links. These interconnecting elements are commonly referred to as struts.
  • struts Presently, there are a wide variety of strut patterns known in the art.
  • the stent of the present invention includes generally a plurality of cylindrical rings that are interconnected by a plurality of links.
  • Each of the cylindrical rings making up the stent have a proximal end and a distal end and a cylindrical plane defined by a cylindrical outer wall surface that extends circumferentially between the proximal end and the distal end of the cylindrical ring.
  • the cylindrical rings typically comprise a plurality of alternating peaks and valleys, where the valleys of one cylindrical ring are circumferentially offset from the valleys of an adjacent cylindrical ring.
  • the connecting links attach each cylindrical ring to an adjacent cylindrical ring so that the links are positioned substantially within one of the valleys and attach the valley to an adjacent peak.
  • the cylindrical rings are interconnected by at least one connecting link between adjacent cylindrical rings and each connecting link may be circumferentially offset from the previous connecting link in a preceding ring.
  • cylindrical rings and connecting links generally are not separate structures, they have been conveniently referred to as rings and links for ease of identification.
  • the cylindrical rings can be thought of as comprising a series of U's, W's and Y-shaped structures in a repeating pattern. Again, while the cylindrical rings are not divided up or segmented into U's, W's and Y's, the pattern formed by the rings resembles such a configuration.
  • the U's, W's and Y's promote flexibility in the stent primarily by flexing and by tipping radially outwardly as the stent is delivered through a tortuous vessel.
  • the present invention stent not only is more visible under fluoroscopy, it also is more compatible for magnetic resonance imaging (MRI) .
  • MRI magnetic resonance imaging
  • the technique for viewing a stent by MRI is different than that under fluoroscopy, it is anticipated that the present invention stent will have more useful visibility under MRI in terms of being able to image near the stent and inside the stent lumen, during placement of the stent, and during follow-up procedures.
  • the stent of the invention may be formed from a tube by laser cutting the pattern of cylindrical rings and connecting links in the tube.
  • the stent also may be formed by laser cutting a flat metal sheet in the form of the rings and links, and then rolling the pattern into the shape of the cylindrical stent and providing a longitudinal weld to form the stent.
  • Other methods of forming stents are well known and include chemically etching a flat metal sheet and rolling and then welding it to form the stent, or coiling a wire to form the stent.
  • hoops or rings may be cut from tubing stock, the tube elements stamped to form crowns, and the crowns connected by welding or laser fusion to form the stent.
  • FIGURE 1 is an elevational view, partially in section, depicting a stent embodying features of the invention and which is mounted on a balloon dilatation catheter and disposed within an artery.
  • FIG. 2 is an elevational view, partially in section, similar to that shown in
  • FIG. 1 depicting the stent expanded within the artery, so that the stent embeds within the arterial wall.
  • FIG. 3 is an elevational view, partially in section, showing the expanded stent implanted in the artery wall after withdrawal of the balloon catheter.
  • FIG.4 is a perspective view of a stent embodying features of the invention, shown in an unexpanded state.
  • FIG. 5 is a perspective view of a stent embodying features of the invention shown, in an expanded state.
  • FIG. 6 is a plan view of a flattened section of the stent of the invention illustrating the pattern of the stent shown in FIG. 4.
  • the present invention stent improves on existing stents by utilizing the heretofore unappreciated properties of certain binary alloys of tantalum and in particular the properties of tantalum-tungsten and tantalum-niobium alloys. Stents produced from these alloys may have tailored wall or strut thicknesses such that the stents are sufficiently radiopaque to be readily visualized under fluoroscopy during a stent placement procedure, yet are not so radiopaque as to interfere with the visualization of surrounding body tissue or stent lumen. In addition, since the stent is produced from a single material, the present invention stent overcomes the drawbacks associated with composite or plated stents, namely corrosion and separation of the radiopaque layer.
  • the stent of the present invention can have virtually any configuration that is compatible with the body lumen in which it is implanted.
  • stents are composed of an intricate geometric pattern of cylindrical rings and connecting links. These elements are commonly referred to as struts.
  • the struts are arranged in patterns which are designed to contact the lumen walls of a vessel and to maintain patency of the vessel thereby.
  • a myriad of strut patterns are known in the art for achieving particular design goals.
  • a few of the more important design characteristics of stents are radial or hoop strength, expansion ratio or coverage area, and longitudinal flexibility.
  • One strut pattern may be selected over another in an effort to optimize those parameters that are of importance for a particular application. An exemplary strut pattern will be described below.
  • Ta-W tantalum-tungsten
  • Ta-Nb tantalum-niobium
  • Table 1 A comparison of the relevant mechanical properties of tantalum-tungsten (“Ta-W”) and tantalum-niobium (“Ta-Nb”) alloys with respect to stainless steel type 316L and pure tantalum are compiled in Table 1.
  • the type 300 series stainless steel is most commonly used in stent applications with type 316L generally being preferred.
  • a tantalum stent will be approximately twice as radiopaque as the same stent produced from stainless steel.
  • material thickness and radiopacity There is also a generally linear relationship between material thickness and radiopacity.
  • the stent with the greater strut thickness will be proportionately more radiopaque.
  • the radial or hoop strength of a stent varies, generally, as a function of the strut thickness cubed (t 3 ). For this reason, stents utilizing identical stent patterns and being designed to have substantially the same radial strength may have comparatively large differences in strut thickness as result of apparently small differences in material yield strength.
  • initial delivery diameter refers to the stent's diameter when it is crimped about an inflation balloon
  • stent' s expanded diameter refers to the diameter of the stent as implanted in a vessel lumen.
  • pure tantalum has about twice the density of stainless steel, while having only about two thirds of the yield strength of stainless steel. Therefore, for a given stent pattern, a tantalum stent generally requires a greater strut thickness than a stainless steel stent to achieve equivalent radial strength. This factor in combination with the material's high density yields a highly radiopaque stent that is excessively bright under fluoroscopy and which obscures the image of the surrounding tissue and lumen. In addition, the greater strut thickness leads to a larger initial delivery diameter than that of stainless steel stent of the same pattern. Large initial delivery diameters or profiles are generally regarded as undesirable. Thus, a pure tantalum stent is generally less suitable for repair of a vessel lesion than a similar stainless steel stent in most applications.
  • tantalum (“Ta”) is alloyed with tungsten (“W”)
  • W tungsten
  • the strength of the binary alloy is substantially greater than that of pure tantalum.
  • Alloys consisting of tantalum and about 2.5% by weight tungsten have a yield strength comparable to that of type 316L stainless steel.
  • Tungsten-tantalum alloys comprising 10% by weight tungsten have a yield strength approaching twice that of type 316L stainless steel.
  • tungsten has only a slightly greater density than tantalum, thus alloying tantalum with a small percentage of tungsten, while having a substantial effect on strength, only marginally increases the density of the binary alloy over that of pure tantalum.
  • Ta-10%W alloy has greater strength than pure tantalum, while retaining a similar density, certain goals may be achieved with the binary alloy which cannot be achieved with pure tantalum. Namely, the higher strength of the binary alloy allows for the stent' s strut thickness to be reduced from that of a type 316L stainless steel stent, while maintaining equivalent radial strength. Reducing the strut thickness directly reduces the radiopacity of the stent and also reduces the initial delivery diameter of the stent.
  • tantalum-tungsten stent with optimum radiopacity and radial strength equivalent to that of a stainless steel stent with .0002 inch thick struts may be produced from tantalum alloys comprising about 2.5% to 15% tungsten by weight. Such a stent will have a strut thickness of about 0.0016 inch.
  • tantalum-tungsten alloys stents may be produced which have superior radiopacity and lower initial delivery profiles than can be achieved with stainless steel or pure tantalum.
  • Niobium has a density of about 10 g/cm 3 which is somewhat greater than the density of stainless steel and substantially less than the density of pure tantalum.
  • an alloy of tantalum comprising 40% by weight niobium has a density of about 12.1 g/cm 3 with a yield strength similar to that of type 316L stainless steel.
  • a Ta- 40%Nb stent will have a radial strength comparable to that of a stainless steel stent and a radiopacity between that of a stainless steel stent and a pure tantalum stent when all three stents have the same pattern and strut thickness.
  • An additional advantage of both Ta-W and Ta-Nb alloys over that of stainless steel is that these alloys form a passive oxide film primarily composed of tantalum oxide (Ta 2 0 5 ), which is generally more durable and more corrosion resistant than the cliromium- oxide film formed during the passivation of stainless steel stents.
  • Ta-W and Ta-Nb alloys are far superior to stainless steel.
  • tantalum- and niobium-based materials are commonly used in the chemical process industries to handle sulfuric and hydrochloric acid solutions that would rapidly attack 316L stainless steel.
  • the above described alloys may be obtained from Cabot Performance Materials, P.O. Box 1607, 144 Holly Road, Boyertown, PA 19512.
  • the following table provides a list of the elements present in each alloy along with their precentages by weight. These are typical or average values.
  • a stent 10 ofthe present invention is shown mounted on a catheter 12 having a lumen 14 and an inflation member 16.
  • the stent and catheter are shown inside a lumen 22 of an arterial vessel 24.
  • the stent is shown positioned across a small amount of arterial plaque 23 adhering to the lumen of the artery.
  • a stent is directly implanted without a prior procedure, such as balloon angioplasties.
  • the plaque is the remainder of an arterial lesion which has been previously dilated or radially compressed against the walls of the artery or has been partially removed from the artery.
  • Lesion dilation is typically accomplished by an angioplasty procedure, while lesion removal is typically accomplished by an atherectomy procedure.
  • atherectomy procedure typically accomplished by an atherectomy procedure.
  • the treated artery suffers a degree of trauma and in a certain percentage of cases may abruptly collapse or may slowly narrow over a period of time due to neointimal hyperplasia which is referred to as restenosis.
  • the treated artery is often fitted with a prosthetic device, such as the stent 10 of the present invention.
  • the stent provides radial support for the treated vessel and thereby prevents collapse of the vessel 24 and further provides scaffolding to prevent plaque prolapse within the lumen.
  • the stent may also be used to repair an arterial dissection, or an intimal flap, both of which are commonly found in the coronary arteries, peripheral arteries and other vessels.
  • the stent In order to perform its function, the stent must be accurately placed across the lesion site. Therefore, it is critical that the stent be sufficiently radiopaque so that the physician can visually locate the stent under fluoroscopy during the implantation procedure. However, it is equally important that the stent not be too radiopaque. If the stent is overly radiopaque, i.e., too bright, the physician's view of the lumen is compromised.
  • a guiding catheter (not shown) is percutaneously introduced into the cardiovascular system of a patient through the femoral arteries by means of a conventional Seldinger technique and advanced within a patient's vascular system until the distal end of the guiding catheter is positioned at a point proximal to the lesion site.
  • a guide wire 20 and the stent-delivery catheter 12 of the rapid exchange type are introduced through the guiding catheter with the guide wire sliding within the stent-delivery catheter.
  • the guide wire is first advanced out ofthe guiding catheter into the arterial vessel 24 and is directed across the arterial lesion.
  • the stent-delivery catheter is subsequently advanced over the previously advanced guide wire until the stent is properly positioned across the lesion.
  • the dilation balloon 16 is inflated to a predetermined size to radially expand the stent 10 against the inside ofthe artery wall and thereby implant the stent within the lumen 22 ofthe artery.
  • the balloon is then deflated to a small profile so that the stent- delivery catheter may be withdrawn from the patient's vasculature and blood flow resumed through the artery.
  • the rings and links ofthe stent are relatively flat in transverse cross-section, thus after implantation into the artery 24 as shown in FIG. 3, minimal interference with blood flow occurs. Eventually the stent becomes covered with endothelial cell growth which further minimizes blood flow interference.
  • endothelial cell growth which further minimizes blood flow interference.
  • the stent 10 is laser cut from a solid tube.
  • the stent does not possess discreet individual components.
  • the exemplary embodiment ofthe stent 10 is made up of a plurality of cylindrical rings 30 which extend circumferentially around the stent.
  • the stent has an initial delivery diameter 32 as shown in FIG. 4, and an expanded or implanted diameter 34 as shown in FIG. 5.
  • Each cylindrical ring 30 has a cylindrical ring proximal end 36 and a cylindrical ring distal end 38 (see also FIG. 6).
  • Each cylindrical ring 30 defines a cylindrical plane 40 which is a plane defined by the proximal and distal ends of the ring, 36 and 38, and the circumferential extent as the cylindrical ring travels around the cylinder.
  • Each cylindrical ring includes a cylindrical outer wall surface 42 which defines the outermost surface ofthe stent, and a cylindrical inner wall surface 44 which defines the innermost surface ofthe stent.
  • the cylindrical plane 40 follows the cylindrical outer wall surface.
  • each ring may be visualized as being formed from a plurality of W-shaped elements 46, U-shaped elements 48, and Y-shaped elements 50. Interconnecting each cylindrical ring are a plurality of links 52. Typically, each adjacent ring will be connected by at least one connecting link. In the exemplary embodiment, each ring is connected to each adjacent ring by three connecting links which are equally spaced at 120 degree intervals around the circumference ofthe stent. Typically, each connecting link is radially offset from the preceding and succeeding connecting links.
  • the U, W, and Y shaped elements of the cylindrical rings 30 have a plurality of peaks 56 and valleys 58. Each adjacent ring 30 is radially offset from each subsequent ring such that the peaks of one ring are axially aligned with the valleys ofthe next adjacent ring.
  • the connecting links 52 are positioned such that each link is within the valley of a U-shaped ring-element 48 and connects the element to a peak of an adjacent ring.
  • the stent 10 may be produced by several methods including electro- discharge machining, ion milling, and chemical etching. However, the preferred method is to laser cut a thin-walled tubular member, such as a hypotube. In this procedure, a computer controlled laser cuts away portions of the hypotube following a preprogrammed template to form the desired strut pattern. Methods and equipment for laser machining small diameter tubing are known in the art.
  • the laser machining process leaves a thin heat effected zone around the pattern cut in the drawn tube and a resulting surface finish that is somewhat coarse and unsuitable for implantation in living tissue.
  • stents are typically descaled and electro-polished.
  • One method of descaling involves immersing the stents in an alkaline cleaner and ultrasonically agitating the stents for a selected period of time.
  • Another method involves bead blasting stents with fine glass beads.
  • There are other procedures for descaling are well known to those skilled in the art.
  • electro-polishing The principles of electro-polishing are also known in the art.
  • an item to be electro-polished is immersed in an electrolyte which comprises an aqueous acidic solution.
  • the item to be polished is made a positive electrode (anode) and a negative electrode (cathode) is placed in close proximity to the anode.
  • the anode and cathode are connected to a source of electric potential difference with the electrolyte completing the circuit between anode and cathode.
  • metal is dissolved from the anode surface with protrusions being dissolved faster than depressions, thereby producing a smooth surface.
  • the rate of material removal in an electro-polishing process is primarily a function ofthe electrolyte chosen and the current density in the electrolyte fluid.
  • a final step in the electro-polishing process involves passivation of the newly polished surface.
  • residual anions of the acid used in the electrolyte remain in contact with the polished surface.
  • the presence of such surface anions leads to deterioration of the newly polished surface when the residual anions come into contact with calcium and magnesium ions which are commonly found in non- deionized water (ordinary tap water).
  • a passivation bath typically consists of a solution of nitric acid, deionized water, and sodium dichromate.
  • the passivation bath neutralizes the residual anions and leaves a protective, corrosion resistant, strongly adherent, transparent, chromium oxide coating on the newly polished surface.
  • tantalum alloy stents An advantage of tantalum alloy stents is that alloys of tantalum form a tough corrosion resistant (tantalum oxide) coating during initial heat treatment of the alloy which renders the alloy relatively impervious to the corrosive effects of any residual anions that may be left on the stent surface after electro-polishing. Therefore, passivation is generally not required after electro-polishing.
  • Niobium also forms a very corrosion-resistant oxide whose properties are very similar to that of tantalum. Niobium is less corrosion resistant than tantalum at elevated temperatures, but quite similar at room temperature.
  • suitably sized tubing for making the stent 10 will have an outside diameter of about 0.020 - 0.070 inch, with a wall thickness of about 0.003 - 0.007 inch.
  • tubing size will vary depending upon the application. It is preferred that the stent be machined from seamless tubing. However, tubing formed by rolling flat, sheet stock into a cylinder with welded longitudinal edges is also suitable, as is rolled sheet stock which has been drawn through a circular die.
  • a new stent utilizing the heretofore unappreciated properties of tantalum-tungsten and tantalum-niobium alloys has been presented.
  • the new stent is sufficiently radiopaque to be readily visualized using fluoroscopy procedures without the need of an additional radiopaque coating.
  • the new stent possesses strength equivalent to that of a stainless steel stent and may be configured with a smaller initial delivery profile.
  • fluoroscopy utilizing x-rays, is by far the most popular imaging method used to visualize stents. This is the case both during an intervention (delivering a stent) and afterwards in a more diagnostic mode.
  • the present invention stent also is visible under magnetic resonance imaging (MRI).
  • MRI magnetic resonance imaging
  • the technique of MRI works completely differently from that of fluoroscopy.
  • the present invention stent will show up in an MRI image in a fundamentally different way than under x-ray.
  • the present invention metal stent will show up in an MRI image by the formation of imaging artifacts.
  • the sources of the imaging artifacts for the present invention stent includes magnetic susceptibility and electrical conductivity. Any metal that has a magnetic susceptibility different from that of tissue will generate a susceptibility artifact. The magnitude of the artifact depends on how much the susceptibility differs from that of tissue. These artifacts usually are signal voids or dark spots on the image. Electrically conductive metals in an MRI scanner can also have electrical currents induced in them by the radio frequency pulses.
  • Stents made of the present invention composition are amongst the most MRI-compatible, while the prior art stainless steel stents are the least MRI compatible.

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  • Health & Medical Sciences (AREA)
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Abstract

L'invention concerne un stent tubulaire fabriqué à partir d'un alliage binaire dont les constituants primaires sont soit du tantale-tungstène soit du tantale-niobium. Ce stent fournit une radio-opacité optimale pour une visualisation en temps réel de celui-ci pendant son opération de placement, au cours de laquelle la fluoroscopie est utilisée en tant que procédé de visualisation. L'alliage binaire peut être incorporé dans une multitude de modèles de stent.
PCT/US2001/020512 2000-07-14 2001-06-28 Stent radio-opaque en alliage binaire WO2002005863A1 (fr)

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JP2002511794A JP2004503334A (ja) 2000-07-14 2001-06-28 二元合金でできた放射線不透過性ステント
EP01948783A EP1301224A1 (fr) 2000-07-14 2001-06-28 Stent radio-opaque en alliage binaire
AU2001270216A AU2001270216A1 (en) 2000-07-14 2001-06-28 Radiopaque stent composed of a binary alloy

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Cited By (26)

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WO2003094735A1 (fr) * 2002-05-07 2003-11-20 Boston Scientific Limited Materiau adapte permettant d'ameliorer la radioopacite
EP1403390A1 (fr) * 2002-09-27 2004-03-31 W.C. Heraeus GmbH & Co. KG Alliage de Nb-Ta-Zr pour la fabrication de Stents
EP1444993A1 (fr) * 2003-02-10 2004-08-11 W.C. Heraeus GmbH & Co. KG Alliage métallique amélioré pour des articles médicaux et des implants
WO2006036786A2 (fr) * 2004-09-27 2006-04-06 Cook Incorporated Dispositifs compatibles avec l'imagerie par resonance magnetique
US7101391B2 (en) 2000-09-18 2006-09-05 Inflow Dynamics Inc. Primarily niobium stent
US7128756B2 (en) 2002-05-08 2006-10-31 Abbott Laboratories Endoprosthesis having foot extensions
US7297157B2 (en) 2002-10-02 2007-11-20 Boston Scientific Scimed, Inc. Medical device with radiopacity
EP1868528A2 (fr) * 2005-03-03 2007-12-26 Icon Medical Corp. Procede de fabrication d'un stent en alliage metallique ameliore
US7402173B2 (en) 2000-09-18 2008-07-22 Boston Scientific Scimed, Inc. Metal stent with surface layer of noble metal oxide and method of fabrication
WO2008134439A1 (fr) * 2007-04-27 2008-11-06 H.C. Starck Inc. Alliage à base de tantale résistant à la corrosion aqueuse
WO2008141336A1 (fr) * 2007-05-15 2008-11-20 Abbott Laboratories Marqueurs radio-opaques et dispositifs médicaux comprenant des alliages binaires de titane
US7625401B2 (en) 2003-05-06 2009-12-01 Abbott Laboratories Endoprosthesis having foot extensions
US7625398B2 (en) 2003-05-06 2009-12-01 Abbott Laboratories Endoprosthesis having foot extensions
WO2008100852A3 (fr) * 2007-02-13 2009-12-03 Abbott Cardiovascular Systems Inc. Alliages radio-opaques compatibles avec l'irm à utiliser dans les dispositifs médicaux
US7637935B2 (en) 2002-05-06 2009-12-29 Abbott Laboratories Endoprosthesis for controlled contraction and expansion
US7727273B2 (en) 2005-01-13 2010-06-01 Boston Scientific Scimed, Inc. Medical devices and methods of making the same
US20100305682A1 (en) * 2006-09-21 2010-12-02 Cleveny Technologies Specially configured and surface modified medical device with certain design features that utilize the intrinsic properties of tungsten, zirconium, tantalum and/or niobium
WO2010144024A1 (fr) * 2009-06-10 2010-12-16 Cederroth Ab Plâtre ou pansement détectable aux rayons x
CN101939123A (zh) * 2007-12-19 2011-01-05 爱尔康医药有限公司 一种用于形成管状医疗器械的方法
US8377111B2 (en) 2003-09-16 2013-02-19 Boston Scientific Scimed, Inc. Medical devices
US8500787B2 (en) 2007-05-15 2013-08-06 Abbott Laboratories Radiopaque markers and medical devices comprising binary alloys of titanium
US8915954B2 (en) 2003-05-06 2014-12-23 Abbott Laboratories Endoprosthesis having foot extensions
US9187802B2 (en) 2009-07-07 2015-11-17 H.C. Stark Inc. Niobium based alloy that is resistant to aqueous corrosion
EP2852353A4 (fr) * 2012-05-21 2016-05-25 Univ Cincinnati Procédés de fabrication d'endoprothèses biodégradables à base de magnésium pour des applications d'implant médical
US9470462B2 (en) 2012-12-14 2016-10-18 TITAN Metal Fabricators Heat exchanger for heating hydrochloric acid pickling solution, a system and method for pickling, and a method of manufacturing steel products
US9546837B1 (en) 2015-10-09 2017-01-17 Bh5773 Ltd Advanced gun barrel

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JP5461202B2 (ja) * 2007-03-09 2014-04-02 アイコン メディカル コーポレーション 医療用具用生体吸収性コーティング
US20190175326A1 (en) * 2016-08-25 2019-06-13 Mico Innovations, Llc Neurovascular Stent

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US7604703B2 (en) 2000-09-18 2009-10-20 Boston Scientific Scimed, Inc. Primarily niobium stent
US7402173B2 (en) 2000-09-18 2008-07-22 Boston Scientific Scimed, Inc. Metal stent with surface layer of noble metal oxide and method of fabrication
US7101391B2 (en) 2000-09-18 2006-09-05 Inflow Dynamics Inc. Primarily niobium stent
US7637935B2 (en) 2002-05-06 2009-12-29 Abbott Laboratories Endoprosthesis for controlled contraction and expansion
US7398118B2 (en) 2002-05-07 2008-07-08 Boston Scientific Scimed, Inc. Customized material for improved radiopacity
WO2003094735A1 (fr) * 2002-05-07 2003-11-20 Boston Scientific Limited Materiau adapte permettant d'ameliorer la radioopacite
US6904310B2 (en) 2002-05-07 2005-06-07 Scimed Life Systems, Inc. Customized material for improved radiopacity
US7128756B2 (en) 2002-05-08 2006-10-31 Abbott Laboratories Endoprosthesis having foot extensions
US7559947B2 (en) 2002-05-08 2009-07-14 Abbott Laboratories Endoprosthesis having foot extensions
EP1403390A1 (fr) * 2002-09-27 2004-03-31 W.C. Heraeus GmbH & Co. KG Alliage de Nb-Ta-Zr pour la fabrication de Stents
US7967854B2 (en) 2002-10-02 2011-06-28 Boston Scientific Scimed, Inc. Medical devices and methods of making the same
EP1549250B1 (fr) * 2002-10-02 2008-04-16 Boston Scientific Limited Dispositifs medicaux et leurs procedes de fabrication
US7682649B2 (en) 2002-10-02 2010-03-23 Boston Scientific Scimed, Inc. Medical devices and methods of making the same
US7297157B2 (en) 2002-10-02 2007-11-20 Boston Scientific Scimed, Inc. Medical device with radiopacity
EP1444993B2 (fr) † 2003-02-10 2013-06-26 W.C. Heraeus GmbH Alliage métallique amélioré pour des articles médicaux et des implants
US8403980B2 (en) 2003-02-10 2013-03-26 Heraeus Materials Technology Gmbh & Co. Kg Metal alloy for medical devices and implants
US7582112B2 (en) 2003-02-10 2009-09-01 Boston Scientific Scimed, Inc. Metal stent with surface layer of noble metal oxide and method of fabrication
CN1321208C (zh) * 2003-02-10 2007-06-13 W.C.贺利氏股份有限及两合公司 改进的用于医用器械和移植物的金属合金
EP1444993A1 (fr) * 2003-02-10 2004-08-11 W.C. Heraeus GmbH & Co. KG Alliage métallique amélioré pour des articles médicaux et des implants
US8349249B2 (en) 2003-02-10 2013-01-08 Heraeus Precious Metals Gmbh & Co. Kg Metal alloy for medical devices and implants
US8915954B2 (en) 2003-05-06 2014-12-23 Abbott Laboratories Endoprosthesis having foot extensions
US7625401B2 (en) 2003-05-06 2009-12-01 Abbott Laboratories Endoprosthesis having foot extensions
US7625398B2 (en) 2003-05-06 2009-12-01 Abbott Laboratories Endoprosthesis having foot extensions
US8377111B2 (en) 2003-09-16 2013-02-19 Boston Scientific Scimed, Inc. Medical devices
WO2006036786A3 (fr) * 2004-09-27 2006-06-15 Cook Inc Dispositifs compatibles avec l'imagerie par resonance magnetique
WO2006036786A2 (fr) * 2004-09-27 2006-04-06 Cook Incorporated Dispositifs compatibles avec l'imagerie par resonance magnetique
US7727273B2 (en) 2005-01-13 2010-06-01 Boston Scientific Scimed, Inc. Medical devices and methods of making the same
US7938854B2 (en) 2005-01-13 2011-05-10 Boston Scientific Scimed, Inc. Medical devices and methods of making the same
EP1868528A4 (fr) * 2005-03-03 2011-04-06 Icon Medical Corp Procede de fabrication d'un stent en alliage metallique ameliore
EP1868528A2 (fr) * 2005-03-03 2007-12-26 Icon Medical Corp. Procede de fabrication d'un stent en alliage metallique ameliore
US8769794B2 (en) 2006-09-21 2014-07-08 Mico Innovations, Llc Specially configured and surface modified medical device with certain design features that utilize the intrinsic properties of tungsten, zirconium, tantalum and/or niobium
US20100305682A1 (en) * 2006-09-21 2010-12-02 Cleveny Technologies Specially configured and surface modified medical device with certain design features that utilize the intrinsic properties of tungsten, zirconium, tantalum and/or niobium
WO2008100852A3 (fr) * 2007-02-13 2009-12-03 Abbott Cardiovascular Systems Inc. Alliages radio-opaques compatibles avec l'irm à utiliser dans les dispositifs médicaux
US9725793B2 (en) 2007-04-27 2017-08-08 H.C. Starck Inc. Tantalum based alloy that is resistant to aqueous corrosion
WO2008134439A1 (fr) * 2007-04-27 2008-11-06 H.C. Starck Inc. Alliage à base de tantale résistant à la corrosion aqueuse
US11001912B2 (en) 2007-04-27 2021-05-11 H.C. Starck Inc. Tantalum based alloy that is resistant to aqueous corrosion
US10422025B2 (en) 2007-04-27 2019-09-24 H.C. Starck Inc. Tantalum based alloy that is resistant to aqueous corrosion
US9957592B2 (en) 2007-04-27 2018-05-01 H.C. Starck Inc. Tantalum based alloy that is resistant to aqueous corrosion
EP3266892A1 (fr) * 2007-04-27 2018-01-10 H. C. Starck Inc Alliage à base de tantale résistant à la corrosion aqueuse
US8500787B2 (en) 2007-05-15 2013-08-06 Abbott Laboratories Radiopaque markers and medical devices comprising binary alloys of titanium
US8500786B2 (en) 2007-05-15 2013-08-06 Abbott Laboratories Radiopaque markers comprising binary alloys of titanium
WO2008141336A1 (fr) * 2007-05-15 2008-11-20 Abbott Laboratories Marqueurs radio-opaques et dispositifs médicaux comprenant des alliages binaires de titane
CN101939123A (zh) * 2007-12-19 2011-01-05 爱尔康医药有限公司 一种用于形成管状医疗器械的方法
WO2010144024A1 (fr) * 2009-06-10 2010-12-16 Cederroth Ab Plâtre ou pansement détectable aux rayons x
US9580773B2 (en) 2009-07-07 2017-02-28 H.C. Starck Inc. Niobium based alloy that is resistant to aqueous corrosion
US9187802B2 (en) 2009-07-07 2015-11-17 H.C. Stark Inc. Niobium based alloy that is resistant to aqueous corrosion
EP2852353A4 (fr) * 2012-05-21 2016-05-25 Univ Cincinnati Procédés de fabrication d'endoprothèses biodégradables à base de magnésium pour des applications d'implant médical
US9470462B2 (en) 2012-12-14 2016-10-18 TITAN Metal Fabricators Heat exchanger for heating hydrochloric acid pickling solution, a system and method for pickling, and a method of manufacturing steel products
US9546837B1 (en) 2015-10-09 2017-01-17 Bh5773 Ltd Advanced gun barrel

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