Method for reducing stent weld profiles and a stent having reduced weld profiles and a closed-end wire configuration

The present invention relates to a stent in which each part is welded and both ends are in a non-traumatic loop shape. The present invention is also such a stent in which the weld is electrochemically polished to reduce the profile and / or the suture loop is one of the extremes or A stent that is threaded on both sides and / or is manufactured using wire with a radiation opaque core and / or is wholly or partially coated with a polymer such as silicone. Is related to.

Stents manufactured by interconnecting (often braiding) elongated wires are made less traumatic, i.e., non-traumatic by closing the loose wire ends at both ends of the stent. Loose wire ends are typically closed by mechanical means such as clamping or welding of clamped microtubules. However, the region provided by such mechanical means has a higher profile (contour, cross-sectional shape) than the other regions of the stent, see, for example, US Pat. No. 6,083,257 (Patent Document 1). Areas with high profiles are not desirable and often lead to regrettable deployments, including increased spread power.

As described above, the laser-cut nitinol stent is subjected to electropolishing or electrochemical polishing to improve the surface finish, for example, US Pat. No. 6,325,825 (Patent Document 2) and US Patent Application Publication No. 2. 2003/0024534 See A1 (Patent Document 3). In addition, electropolishing or electrochemical polishing services are also available, see, for example, the services of Admedes Schuessler GmbH). However, such a polishing process has never been attempted to eliminate the above-mentioned unfortunate situation in terms of deployment.

<patcit num="1"><text>U.S. Pat. No. 6,083,257</text></patcit><patcit num="2"><text>U.S. Pat. No. 6,325,825</text></patcit><patcit num="3"><text>U.S. Patent Application Publication No. 2003/0024534 A1</text></patcit><patcit num="4"><text>U.S. Patent Application Publication No. 2002/0035396 A1</text></patcit>

<p> The present invention provides a stent made from elongated wire with a closed end design while avoiding the disadvantages of the prior art. In particular, the present invention aims to reduce the dispersal force of a stent and facilitate its deployment by an advantageous closed stent loop design with reduced profiles.</p>

<p> One aspect of the present invention is<u style="single">A method of producing a implantable stent. In this method, a step of providing a plurality of elongated stent wires having a diameter and a step of forming a plurality of wires into the shape of a hollow tubular structure and providing a first open end and a second open end at both ends thereof. And a step of terminating a plurality of wires at the second open end, and a step of aligning the plurality of wires with each other at the second open end to form a plurality of adjacent wires paired with each other to determine a plurality of contact areas. , 25% to 50 weight of the weld material of multiple welds, with the process of defining multiple welds by welding multiple adjacent wires in pairs to each other at the abutment area and the method of choice. Includes a step of chemically or electrochemically removing the% to reduce the profile of the weld so that it is shorter than the diameter of the stent wire.</u>It is desirable that the plurality of adjacent wires paired with each other be substantially parallel to any of the contact areas.</p><p> From this point of view of the present invention, the welding step may include the step of donating the inert gas proximal to the welding region. Further, specific examples of the welding process include laser welding, electron beam welding, resistance welding, tungsten inert gas welding, metal inert gas welding, and combinations thereof.</p><p> The process of forming the tubular structure preferably includes braiding the wire, winding the wire, knitting the wire, and combining these, but braiding the wire is preferable. preferable. The material of the wire and the material of the welded portion may be the same type of material.</p><p> Further, as a specific example of the stent wire, there is a radiation permeable material and the like.</p><p> Specific examples of the steps of chemically or electrochemically removing a part of the welding material include chemical polishing, chemical etching, chemical debrising, electrochemical polishing, or electrochemical etching, injection-electrochemical polishing, and these. There are combinations of. The step of electrochemically removing a part of the welding material further includes the step of donating the electrolytic solution, in which case the electrolytic solution is NaClO.₃Electrolyte, NaNO₃Electrolyte, NaCl electrolyte, Na₂Cr₂O₇Electrolyte, HOCH₂CH₂Examples thereof include an OH electrolytic solution and a combination thereof.</p><p> More specifically, the steps of electrochemically removing a part of the welding material include (i) a step of supplying an electrolytic solution, (ii) a step of installing a cathode in the electrolytic solution, and (iii) welding. By placing a part of the weld containing the material in the electrolytic solution and (iv) applying a voltage or current, the cathode becomes negatively charged and the stent becomes positively charged. It may further include (v) a step of partially dissolving the stent portion exposed to the electrolyte.</p><p> From another aspect of the present invention, the stent manufacturing method of the present invention includes (i) a step of extending at least one of a set of wires to provide an extension stent wire, and (ii) looping the extension stent wire. Further includes a step of bringing the extension end into contact with a pair of proximal stent wires and (iii) a step of welding the extended looped wire to a pair of proximal stent wires. You may be. The looping process involves forming the wire into a bow with equilateral vertices, but preferably with no sharp inflection points other than one cusp. The looping process makes the wire arcuate with one apex on the same side, but preferably involves shaping the wires so that the curvatures on both sides of the apex are the same. The bow does not contain a second vertex and sides of different curvature on either side of such a second vertex.</p><p> In another aspect of the present invention, the method for manufacturing a stent includes (i) a step of extending at least one of the paired stent wires to a position beyond the contact region and providing the extended stent wire. (ii) It further includes the step of looping the extension stent wire at its extension end and forming a coil at that position. Multiple extension wires may be used to form a single coil or pig caudal winding.</p><p> The elongated wire is a biocompatible material selected from the group consisting of nitinol, stainless steel, cobalt-based alloys such as Elgiloy®, platinum, gold, titanium, tantalum, niobium, and combinations thereof. It is preferably composed of, but nitinol is preferred. The elongated wire is a composite that improves radiation permeability, such as with an inner core made of tantalum, gold, platinum, iridium, or a combination thereof, and an outer layer or member of nitinol. It may be a wire.</p><p> Another aspect of the invention provides a implantable stent. In the stent of this aspect of the present invention, a plurality of wires are arranged to form a hollow tubular structure having a tubular wall defining an inner wall and an outer wall and having a first open end and a second open end at both ends. Here, the wires are terminated at the second open end, and the wires that are in contact with each other adjacent to each other are welded to the welding material at the second open end to provide a welded portion, and further, of the welding material. At least part of it has been removed to reduce the profile of the weld. It is desirable that some of the weld material be removed by chemical or electrochemical polishing. It is preferred that at least 25% to 50% by weight of the stent material at or near the weld is removed.<u style="single">。</u></p><p> Stents are composed of wires made from biocompatible materials, such as nitinol, stainless steel, cobalt-based alloys such as Elgiloy®, platinum, gold, titanium, etc. There are tantalum, niobium, and combinations thereof. The weld material and wire material may be the same, for example both may be nitinol. Further, the elongated wire is composed of an inner core material made of tantalum, gold, platinum, iridium, or a combination thereof, and an outer member of nitinol.</p><p> In another aspect of the invention, at least one of the plurality of adjacent and abutting stent wires extends beyond the weld and is looped to form a single apex on the equilateral side. It has a bow shape, but there are no sharp bending points other than this apex, that is, some of the stent wires that are adjacent to each other and abut each other extend beyond the welding point. Is looped into a bow with one vertex on the same side, but the curvatures on both sides of this vertex are the same, in which case the bow design is with the second vertex and so on. It does not contain sides with different curvatures on either side of the vertices. As an alternative example, at least some of the stent wires that abut adjacent to each other extend beyond the welding point and are looped to form a coil at that location, forming a pig tail-like winding. It becomes. As another alternative, at least some of the stent wires that abut adjacent to each other extend beyond the welding point and are looped to form a coil at that location.</p><p> The stent wire may be coated, for example with silicone. In addition, the stent may be entirely or partially covered with a polymer coating such as silicone to prevent tissue growth or tumor growth.</p><p> The stent may be such that a hollow tubular implant is placed on the inner or outer surface. The implant may be a polymer material, for example, polyester, polypropylene, polyethylene, polyurethane, polynaphthalene, polytetrafluoroethylene, foamed polytetrafluoroethylene, silicone, or a combination thereof.</p><p> The stent is preferably a braided stent.</p><p> The stent may have a polymer ring further placed on the outer surface at the second open end. In addition to this, the stent may also be such that the suture is secured to one of both open ends. Such sutures (s) are useful for placing, repositioning, and / or removing the stent. The suture is a metal, polymer, or woven suture loop that is threaded through the stent loop at one or both extremes of the stent. The suture loop is provided with a protrusion, which can facilitate the capture or grip of the stent end.</p><p> In another aspect of the invention, implantable stents are hollow with multiple wires arranged to provide tubular walls that define the inner and outer surfaces, as well as first and second open ends at both ends. In this case, a plurality of wires are terminated at the second open end, and the wires that are in contact with each other adjacent to each other are welded to the welding material at the second open end to provide a welded portion. Also, at least part of the weld material is removed by chemical or electrochemical polishing to reduce the profile of the weld.</p>

The present invention overcomes the shortcomings of the prior art, among other things, by providing low profile stents (stents with low contour, cross-sectional shape) that reduce the spreading force of the stent. FIG. 1 depicts the stent 10 of the present invention. The stent 10 is a hollow tubular structure, which is provided with open ends 12 and 14 at both ends and a tubular wall 16 between both ends. A portion of the tubular wall 16 is depicted in FIG. 2 as a plurality of elongated wires 18 formed into the tubular wall 16. The elongated wire 18 traverses the elongated portion of the stent 10 in a direction crossing the elongated portion in the longitudinal direction of the stent 10. In forming the elongated wire 18 into the tubular wall 16, there is a method of braiding the wire 18, forming the wire 18 into a winding shape, knitting the wire 18, or performing a combination process thereof. The wire 18 is preferably braided to form a tubular wall 16.

The welded stent 10'according to the present invention is depicted in FIG. The elongated wires 18 terminating at the open end 12 are assembled, and the wires that are assembled adjacent to each other are all fixed by the welding portion 20. It is depicted in more detail in FIG. 4 that three wires 18 in a pair adjacent to each other are joined and welded at the joining position. The process of installing the wires that are paired adjacent to each other so as to form a closed-end loop end type is May 2003, except for the closed-end arcuate loop type of the present invention described below. As further explained in US Application No. 60 / 472,929 filed on the 23rd, this application is equivalent to US Application No. 10 / 852,495, US2005 / 0049682. Although it is published as A1 (Patent Document 4), its contents shall be a part of this case by incorporating it here. The welded portion 20 is a low profile welded portion, that is, a welded portion having a smaller welding area than the stent welded portion of the prior art. The stent 10'depicted in FIG. 3 consists of 24 wires 18 of nitinol or a nitinol-containing material. These wires are relatively thin at sites with a diameter of about 0.2794 mm (about 0.011 inch). The number of wires and the diameter of the wires depicted in FIG. 3 may all be the same or may be different from each other, but the number is not limited to this, and the number of wires other than the above is not limited to the above. Alternatively, wires having a diameter other than the above can also be preferably used.

A pair of adjacent welded wires according to the invention are depicted in FIGS. 5-8. The welded portion 24 firmly joins the stent wires 22 which are adjacent to each other. Compared with the prior art, the welded portion 24 of the present invention has a significantly reduced amount of welding material at that portion. The weld 24 contains at least about 25% or less of the weld material than the prior art weld, specifically it is desirable that the weld material be reduced by about 25% to about 50%. As an alternative example, the weld 24 is the diameter d of the wire 22.₁Shorter profile, i.e. d₁Shorter depth d₂And / or width d₄Is provided. As another example, or in addition to the above examples, the welded portion 24 of the present invention preferably has a profile of about 150 microns or less, preferably in the range of about 50 microns to about 150 microns. As yet another example, or in addition to the above-mentioned examples, each part of the welded portion 24'and the stent wire 22'proximal to the welded portion 24'of the present invention has a reduced profile, and here, welding is performed. The profile of the portion 24'is smaller than the profile of the welded portion 24, and the diameter d of the proximal stent portion 22'₂Is the diameter d of the stent wire part 22₁Shorter than. The mass and volume of the welded portion 24'and / or the mass and volume of the stent portion 22' are suitably reduced by chemical polishing or electrochemical polishing. The reduced profile welds 24, 24'of the present invention provide a method for removing excess weld material in overcoming the difficulty of constraining stents 10, 10'on a transport device (not shown). Although adopted, such excess welding material, if not removed, will increase the localized binding force of the weld site when compared to other parts of the stent 10, 10'.

Specific examples of useful welding methods include, but are not limited to, laser welding, electron beam welding, resistance welding, tungsten inert gas welding, metal inert gas welding, and combinations thereof. In laser welding and electron beam welding, the wire is partially melted by the energy provided by the laser beam or electron beam. In gas tungsten arc welding (GTAW or TIG welding), an electric arc is formed between the electrodes, usually between the tungsten electrodes, and the metal is welded. In metal inert gas (MIG) welding, an electric arc is generated between the filler-filled electrodes, and at the same time the metal is welded, the metal melted from the filler-filled electrodes is added to the metal being welded. Resistance welding utilizes an electric current application and, in some cases, mechanical pressure to provide a welded portion between two metal pieces. The welded area may be shielded with an inert gas. Examples of the inert gas include argon and a mixture of a gas different from argon and argon, and examples of the latter include a mixture of argon and hydrogen or a mixture of argon and helium, but are limited thereto. is not it.

FIG. 9 depicts an electrochemical cell 30 for forming the low profile welds 24, 24'of the present invention by removing the weld material. In the cell 30, the electrolytic solution 32 is stored in the container 34. A stent 10 having welds 24 and 24'at the stent end 12 is installed in the electrolytic solution 32. The cathode 36 is also installed in the electrolytic solution 32. The wire 38 connects the cathode 36 to the negative terminal 40 of the voltage source or current source 46. The wire 42 connects the stent 10 to the positive terminal 44 of the voltage or current source 46. When a voltage or current is applied from the power supply 46, the cell 30 is put into operation. A material, such as a welding material, dissolves from the stent into the electrolyte 32. As a specific example of a useful electrolyte, NaClO₃Electrolyte, NaNO₃Electrolyte, NaCl electrolyte, Na₂Cr₂O₇Electrolyte, HOCH₂CH₂Examples thereof include an OH electrolytic solution and a combination thereof. Current densities typically range from about 50 amps / centimeter to about 150 amps / centimeter, but are not limited to these. The electrolytic solution 32 may be moved at a low speed or may be in an unstirred state. When the anodic metal is electrochemically dissolved, the solubility is not affected by the hardness of the metal or other physical properties.

The wire 22 is preferably made from nitinol, stainless steel, cobalt-based alloys such as Elgiloy®, platinum, gold, titanium, tantalum, niobium, and combinations thereof. Further, the wire 22 has an inner core made of tantalum, gold, platinum, iridium, or a combination thereof, etc., and an outer member or an outer layer made of nitinol to improve radiation impermeableness, that is, visibility. It is a composite wire. Other details of such composite wires can be found in U.S. Patent Application Publication No. 2002/0035396. As will be clarified in A1, the content of the publication of the application shall be a part of this case by giving a reference. The wire 22 is preferably made from nitinol. In addition, the welding material for filling is nitinol, stainless steel, cobalt-based alloys such as Elgiloy®, platinum, gold, titanium, tantalum, if required in a welding process such as MIG. It is produced from niobium, a combination thereof, etc., but nitinol is preferable. The material of the cathode is not important and may be made from any suitable metal. The filling welding material and the wire 22 can be made from the same material, for example from nitinol.

When chemical polishing or electrochemical polishing 30 removes material from each part of the stent 10 placed in electrolyte 32, welds 24, 24', burrs, or other imperfections (shown). There are several methods for selectively removing materials such as welding from the stent 10. One of the techniques for selectively removing a material is to utilize a photoresist or an insulator, which is an organic polymer or resin that can be applied to the selected region of the stent 10. By insulating the selected region from the action of such a photoresist, the electrochemical polishing of the coated portion 30 can be avoided. For example, as depicted in FIG. 5A, each portion of the stent wire 22 may be photoresist coated prior to placement in cell 30. After the chemical or electrochemical polishing is complete, the photoresist is removed by adding a suitable solvent. As an alternative example, jet electrochemical polishing or jet electrochemical etching can be utilized to specifically etch and remove the welded area. Injection etching includes a process of selectively polishing a desired region such as a stent weld by locally applying an electrolytic solution at an appropriate speed of, for example, about 3 m / s to about 30 m / s. I'm out.

As an alternative example, each part of the welded portions 24 and 24'may be removed by using chemical etching or the like, and each part of the stent wire 22 may be arbitrarily removed. Chemical polishing or chemical etching is similar to the electrochemical method described above, with the exception that an oxidizing acid is added to the electrolyte and no accompanying equipment (current or voltage source, cathode, etc.) is optionally required. .. Specific examples of the electrolytic solution containing an acid for oxidation include an electrolytic solution containing hydrofluoric acid, an electrolytic solution containing nitric acid, and an electrolytic solution containing the combination of the above acids.

However, the present invention is not limited to reducing the profile of welds at exactly that location of wires adjacent to each other at termination points, such as wire 22 in FIG. 5 or FIG. 5A. As depicted in FIGS. 10-14, certain stent wires 56, 62 are extended beyond adjacent wires 50, 54 and then wound in a loop to form proximal wires 52, 60. And wires 50 and 64 may be returned to each. Adjacent portions of the wire 50 and the wire 56 are placed in contact with each other in the contact area 68. Similarly, the adjacent portions of the wire 52 and the wire 60 and the adjacent portions of the extended loop portion 66 are arranged in contact with each other in the abutting region 70, and the adjacent portions of the wire 54 and the wire 66 are in contact with each other. The contact area 72 is arranged in contact with each other, and the adjacent portions of the wire 58 and 64 and the adjacent portion of the extended loop portion 67 are arranged in contact with each other in the contact area 74. The wire portions placed in contact with each other in the contact region are preferably, but are not limited to, substantially parallel to each other, for example, in the range of about ± 10 degrees parallel to each other. Further, it is preferable, but not limited to, the range of the parallel state of about ± 5 degrees.

As depicted in FIG. 11, the wires in the contact areas 68, 70, 72, 74 are fixed by the welded portion 76. The welded portion 76 is a low profile welded portion, and it is desirable that the welded portion 76 has a low profile by electrochemical polishing according to the present invention.

The extended loop portions 66 and 67 are preferably bow-shaped with an equilateral design, but may also be referred to as a cathedral-shaped bow or loop. As depicted in FIG. 12, the equilateral bow loop 78 has cusps or vertices 80. The word "vertex" and its variants, as used in this case, means the intersection of two geometric lines or curves. The word "cusp" and its variants, as used in this case, means the top of the loop or the top of the highest point. With the exception of the cusp 80, the equilateral bow loop 78 preferably has no inflection points defined as regions where the curvatures on both sides of one point are different. In other words, the equilateral bow loop 78 has cusps, but no other acute inflection points. The equilateral bow loop 78 is woven with one vertex (or cusp 80) and contains a second vertex with different curvatures on both sides of that vertex (cusp 80) and sides with different curvatures on both sides. It is desirable not to have it.

The equilateral bow loop design has several advantages, including, for example, a reduction in spreading force as compared to a prior art loop design with multiple vertices or multiple acute angle bends. If the stent is constrained above or within the transport system (not shown), a number of sharp bends in the stent's end loops will collide with the walls of the transport system, leaving its position slightly bitten. As a result, it was customary to distort the outer sheath member of the transport system. As a result, the value of the spreading force is significantly increased. Furthermore, since the equilateral bow loop has only one cusp, that is, a cusp, and is defined by a gradual curvature other than that, the gradual curvature does not cut into the wall of the transport system. The resulting spreading force is significantly reduced.

In another aspect of the invention, as depicted in FIG. 13, the equilateral bow loop 82 has one cusp 82 and multiple vertices 86, as well as a substantially linear portion 88. I have. In such cases, the apex 86 and the linear portion 88 are covered by a low profile weld 90 to join other adjacent stent wires (not shown). The equilateral bow loops 66, 67, 78, 82 of the present invention are suitably formed by wrapping a stent wire around a plurality of forming pins 98 on the mandrel 100, as depicted in FIG. be able to. In addition, one or more sutures (not shown) on one or both ends 12, 14 of stents 10, 10', including end 12 with equilateral bow loops 66, 67, 78, 82. ) May be attached. Such sutures are useful for placing, repositioning and / or removing stents 10, 10'.

In yet another aspect of the invention, the stent 10 may be provided with a design other than the above at the open end 12, which is useful for placing, repositioning and / or removing it. As depicted in FIG. 15, the wires extend from all or some of the wire engaging portions 92 adjacent to each other. The end of the extension wire is formed into coil 90. As depicted in FIG. 16, wires extend from all or some of the wire engaging portions 92 adjacent to each other. The end of the extension wire is formed into a coil 94, which is hook-shaped and is commonly referred to as a pig tail winding. Furthermore, the open end 12 of the stent 10 may be shorter in diameter than the rest of the stent 10. The reduced diameter portion allows the stent 10 to be placed, repositioned and / or easily accessible to the stent end 12 for removal. The stent end 12 of the stent 10 of FIG. 17 may include any of the loops or coils described above at its location. As an alternative to this, or in addition to the previous example, the stent end 12 may have a band 96 placed on it, as depicted in FIG. 18, which band also holds the stent 10. Useful for installation, stenting, and / or removal. Band 96 is made from biocompatible materials such as polymers, plasticizers and metals. The band 96 can be attached to the stent end 12 by adhesive, mechanical or physical means, such as adhesive adhesion, welding, stitching, fusion and the like.

As depicted in FIG. 20, the stent 10 is completely, fully or partially coated, with silicone 102, which is in the form of a tubular structure. Silicone 102 is located on the outer surface 104 of the stent 10 as depicted in FIG. 21, and is located on the inner surface 106 of the stent 10 as depicted in FIG. 22, or a combination of both. You may match.

Regardless of which embodiment of the stent 10, 10'is used, the stent maintains the physical blood vessels in the cardiovascular or peripheral blood vessels, esophagus, trachea, bronchi, colon, bile duct, urinary tract, prostate, brain, etc. in a patented state. can do. Stents 10, 10'can also be treated with any of the following agents: That is, antithrombotic agents (heparin, heparin derivatives, urokinase, PPack (dextrophenylalanine, proline, arginine, chloromethylketone), growth inhibitors (enoxaprin, angiopeptin, or monochrome capable of inhibiting smooth muscle cell proliferation). Nar antibody, hirudin, and acetylsalicylic acid), anti-inflammatory agents (dexametazone, prednisolone, corticosterone, budesonide, estrogen, sulfasalazine, and mesalamine), antitumor / antiproliferative / anticoagulant (pacritaxel, 5) -Fluorouracil, cisplatin, vinblastine, vincristine, eposylone, endostatin, angiostatin, and thymidine kinase inhibitors), anesthetics (lidocane, bupivacaine, ropivacaine, etc.), anticoagulants (D-Phe-Pro-Arg, etc.) Chloromethylketone, RGD peptide-containing compound, heparin, antithrombin compound, platelet receptor antagonist, antithrombin antibody, antiplatelet receptor antibody, aspirin, prostaglandin inhibitor, platelet inhibitor, tick antiplatelet peptide, etc.), vascular cells Growth promoters (growth factor inhibitors, growth factor receptor antagonists, transcriptional activators, translation promoters, etc.), vascular cell growth inhibitors (growth factor inhibitors, growth factor receptor antagonists, transcription inhibitors, translation inhibitors, etc.) Replication inhibitors, inhibitory antibodies, growth factor attack antibodies, bifunctional molecules consisting of growth factors and cytotoxins, bifunctional molecules consisting of antibodies and cytotoxins, etc.), cholesterol-lowering agents, vasodilators, endogenous vasoactive function It can also be treated with any of the drugs that interfere with.

Having described the invention as described above, it will be apparent to those skilled in the art that the invention can be modified in a variety of ways. Such modifications are not considered to deviate from the spirit and scope of the invention and all such modifications should be construed as falling within the scope of each claim of the appended claims. is there.

<figref num="1">It is a perspective view of the hollow tubular stent by this invention.</figref><figref num="2">It is an enlarged view of the wall part which was broken along the axis 2-2 of the stent of FIG. 1, and is the figure which illustrated a plurality of stent wires.</figref><figref num="3">It is a figure which has been drawn that a plurality of welding portions are provided at the closed end of the braided stent of the closed loop design by this invention.</figref><figref num="4">It is an enlarged view of one welding part of FIG.</figref><figref num="5">It is a figure which drew the welded part which joined two stent wires by this invention.</figref><figref num="5A">According to the present invention, an insulator or a photoresist is placed on a selected stent wire portion, and a welded portion in which two stent wires are joined is drawn.</figref><figref num="6">It is sectional drawing which broke the bonded stent wire of FIG. 5 along the axis 6-6.</figref><figref num="7">It is sectional drawing which broke the welded stent wire of FIG. 5 along the axis 7-7.</figref><figref num="8">FIG. 5 is a cross-sectional view of the welded stent wire of FIG. 7 after being subjected to chemical polishing or electrochemical polishing.</figref><figref num="9">It is the schematic of the cell for the electrochemical polishing process by this invention.</figref><figref num="10">It is a figure which drew the arc shape which has the equilateral side and one cusp in the design of the closed end type loop by this invention.</figref><figref num="11">It is a figure which drew the arc shape which has the equilateral side and one cusp in the design of the closed end type loop by this invention.</figref><figref num="12">It is a figure which drew the arc shape which has the equilateral side and one cusp in the design of the closed end type loop by this invention.</figref><figref num="13">It is a figure which drew the arc shape which has the equilateral side and one cusp in the design of the closed end type loop by this invention.</figref><figref num="14">It is a figure which drew the arc shape which has the equilateral side and one cusp in the design of the closed end type loop by this invention.</figref><figref num="15">FIG. 5 is a diagram depicting an embodiment of the design of a closed-end loop of the present invention in which a plurality of coils are provided at the closed end.</figref><figref num="16">Yet another embodiment of the closed-end loop design of the present invention depicts one coil or pig caudal winding at the closed end.</figref><figref num="17">FIG. 5 depicts another embodiment of the present invention in a closed end design arranged on a closed end stent wire.</figref><figref num="18">FIG. 5 depicts another embodiment of the present invention in a closed end design arranged on a closed end stent wire.</figref><figref num="19">FIG. 10 is a diagram depicting a mandrel provided with a forming pin for forming a closed-end loop in FIG.</figref><figref num="20">It is a figure which has drawn the silicone coating provided on the stent by this invention.</figref><figref num="21">FIG. 2 is a cross-sectional view of the stent of FIG. 20, which illustrates the outer coating of silicone on the outer periphery of the stent.</figref><figref num="22">FIG. 2 is a cross-sectional view of the stent of FIG. 20, which illustrates the inner coating of silicone on the inner circumference of the stent.</figref>