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Publication numberWO2002022050 A2
Publication typeApplication
Application numberPCT/US2001/028850
Publication date21 Mar 2002
Filing date12 Sep 2001
Priority date12 Sep 2000
Also published asCA2421797A1, EP1317229A2, WO2002022050A3, WO2002022050A9
Publication numberPCT/2001/28850, PCT/US/1/028850, PCT/US/1/28850, PCT/US/2001/028850, PCT/US/2001/28850, PCT/US1/028850, PCT/US1/28850, PCT/US1028850, PCT/US128850, PCT/US2001/028850, PCT/US2001/28850, PCT/US2001028850, PCT/US200128850, WO 0222050 A2, WO 0222050A2, WO 2002/022050 A2, WO 2002022050 A2, WO 2002022050A2, WO-A2-0222050, WO-A2-2002022050, WO0222050 A2, WO0222050A2, WO2002/022050A2, WO2002022050 A2, WO2002022050A2
InventorsRichard Olson, Timothy Ley
ApplicantScimed Life Systems, Inc.
Export CitationBiBTeX, EndNote, RefMan
External Links: Patentscope, Espacenet
Selectively etched radiopaque intraluminal device
WO 2002022050 A2
Abstract
The present invention relates to intraluminal devices, in particular stents, having radiopaque material selectively affixed thereon, and to a method of making the same.
Claims  (OCR text may contain errors)
CLAIMS:
1. A method of forming a radiopaque intraluminal device having a surface, a distal end, a proximal end, and a body having a center portion said intraluminal device having radiopaque material selectively affixed thereon comprising the steps of: a) providing a preform in the form of a sheet or a tube, optionally having a strut pattern formed therein; and b) affixing at least one radiopaque material to said preform; and c) removing some of the radiopaque material from said preform in preselected areas; wherein said removal step is free of masking.
2. The method of Claim 1 wherein said preform is in the form of a sheet, further comprising the step of forming said preform into a tubular shape.
3. The method of Claim 2 further comprising the step of welding to retain said tubular shape.
4. The method of Claim 1 wherein after said radiopaque material is affixed to said preform, a strut pattern is formed in said preform.
5. The method of Claim 1 wherein before said radiopaque material is affixed to said preform, a strut pattern is formed in said preform.
6. The method of Claim 4 wherein said strut pattern is formed in said preform by a method selected from laser cutting, chemical etching and metal stamping.
7. The method of Claim 5 wherein said strut pattern is formed in said preform by a method selected from laser cutting, chemical etching and metal stamping.
8. The method of Claim 1 wherein the radiopaque material is removed from said patterned preform in preselected areas by a method selected from chemical etching, laser etching, metal stamping, microblasting and machine grinding .
9. The method of Claim 1 wherein the preform comprises at least one metal.
10. The method of Claim 1 wherein the preform comprises an alloy of metals.
11. The method of Claim 1 wherein a plurality of different radiopaque materials are affixed to said preform.
12. The method of Claim 1 wherein said at least one radiopaque material is gold.
13. The method of Claim 1 wherein a strike layer is affixed to said metal sheet before affixing said radiopaque material.
14. The method of Claim 13 wherein said strike layer is gold.
15. The method of Claim 1 wherein said radiopaque material is affixed to said distal 5 end and said proximal end of said device.
16. The method of Claim 1 wherein said intraluminal device is a stent.
17. The method of Claim 1 wherein said radiopaque material is affixed to said distal end, said proximal end, and said center portion of said body of said intraluminal device.
10 18. The method of Claim 17 wherein said intraluminal device is a bifurcated stent.
19. A method of forming a radiopaque intraluminal device having radiopaque material selectively affixed thereon comprising the steps of: a) affixing at least one radiopaque material to an intraluminal device preform in the form of a metal sheet or tube; 15 b) forming a strut pattern in said preform by a method selected from laser cutting, chemical etching and metal stamping; c) removing radiopaque material from said patterned preform in preselected areas; wherein said removal step is free of masking.
20 20. The method of Claim 19 wherein said preform is the form of a metal sheet, further comprising the step of forming said sheet into a tubular shape.
21. The method of Claim 20 further further comprising the step of welding said sheet to retain said tubular shape.
22. The method of Claim 19 wherein said affixing step is immersing in an 25 electroplating solution.
23. The method of Claim 19 wherein said radiopaque material is removed by a method selected from chemical etching, laser cutting, metal stamping, microblasting and machine grinding.
24. A stent having a surface, a distal end, a proximal end, and a center portion, said 30 device having radiopaque material selectively affixed thereon produced by the steps of: a) providing a stent preform in the form of a sheet or a tube; b) affixing at least one radiopaque material to said stent preform; b) forming a strut pattern into said stent preform; and c) removing radiopaque material from said stent preform from preselected 5 areas of said preform wherein said removal step requires no masking; wherein the resultant intraluminal device has radiopaque material on said proximal end, said distal end and around said opening in said center portion of said stent.
25. The stent of Claim 24 wherein said affixing step is immersing in an electroplating 10 solution.
26. The stent of Claim 24 wherein said radiopaque material is gold.
27. The stent of Claim 24 wherein a strike layer is affixed to said metal sheet before affixing said radiopaque material.
28. The stent of Claim 27 wherein said strike layer is gold.
15 29. The stent of Claim 24 wherein the coating thickness of the radiopaque material is varied over the surface of the preform by said removing step.
30. The stent of Claim 24 wherein said radiopaque coating is affixed to said proximal end and said distal end of said stent.
31. The stent of Claim 24 wherein said center portion of said stent further has an 20 opening.
32. The stent of Claim 31 wherein said stent is a bifurcated stent.
33. The stent of Claim 24 wherein said radiopaque material is selectively affixed to said proximal end, said distal end, and around said opening in said center portion of said stent.
25 34. The stent of Claim 24 wherein said radiopaque material is removed by a method selected from chemical etching, laser cutting, metal stamping, microblasting and machine grinding
35. The stent of Claim 24 wherein at least two different radiopaque materials are affixed to said preform. 30
36. A method of forming a radiopaque intraluminal device having a surface, a distal end, a proximal end, and a body having a center portion said intraluminal device having radiopaque material selectively affixed thereon comprising the steps of: a) providing a preform in the form of a sheet or a tube, optionally having a strut pattern formed therein; and b) affixing at least one radiopaque material to said preform wherein the 5 thickness of the radiopaque material is varied over the surface of the intraluminal device by coating some preselected areas of said preform thicker than others.
37. The method of Claim 36 further comprising the step of removing some of the radiopaque material from said preform in preselected areas. 10
38. The method of Claim 36 wherein said radiopaque material is removed by a process selected from laser cutting, chemical etching, metal stamping, microblasting and machine grinding.
39. A method of forming a radiopaque intraluminal device having a surface, a distal end, a proximal end, and a body having a center portion said intraluminal device
15 having radiopaque material selectively affixed thereon comprising the steps of: a) providing a preform in the form of a sheet or a tube, optionally having a strut pattern formed therein; and b) affixing at least two different radiopaque materials to said preform.
40. The method of Claim 39 further comprising a step of removing some of the 20 radiopaque material from said preform in preselected areas.
41. The method of claim 40 wherein said removing step is free of masking, wherein said removal step is free of masking.
42. The method of Claim 39 wherein said radiopaque material is removed by a process selected from laser cutting, chemical etching, metal stamping,
25 microblasting and machine grinding.
43. The method of Claim 39 wherein said at least two different radiopaque materials are tantalum and gold.
44. A method of forming a radiopaque intraluminal device having a surface, a distal end, a proximal end, and a body having a center portion said intraluminal device
30 having radiopaque material selectively affixed thereon comprising the steps of: a) providing a preform in the form of a sheet or a tube, optionally having a strut pattern formed therein; b) coating a first radiopaque material to said preform; and c) further coating a second radiopaque material to selected areas of said preform.
45. The method of Claim 44 wherein said first radiopaque material is the same as said second radiopaque material.
46. The method of Claim 44 wherein said first radiopaque material is different from said second radiopaque material.
47. The method of Claim 44 further comprising a step of removing some of the first radiopaque material, second radiopaque material or both from preselected areas of said preform.
48. The method of Claim 47 wherein said removing step is free of masking.
Description  (OCR text may contain errors)

SELECTIVELY ETCHED RADIOPAQUE INTRALUMINAL DEVICE

FIELD OF THE INVENTION The present invention relates to selectively etched gold plated intraluminal devices, and in particular, to selectively etched gold plated stents. The entire surface of a preform in the form of a metal sheet or tubular shape is electroplated with gold. A strut pattern may be formed in the preform either before or after electroplating. The gold is then removed only in the desired areas using a predetermined strut pattern.

BACKGROUND OF THE INVENTION

Stenoses occur when the diameter of a vessel or an artery becomes narrower most often due to a build-up of fatty deposits on the interior walls of the vessel or artery which ultimately restricts the flow of blood through the vessel. Stents are useful in the treatment of artherosclerotic stenoses in blood vessels and arteries. Stents function to "prop" open the vessel with the stenosis or blockage, and allow an adequate flow of blood through the vessel. They are generally tubular shaped devices that are open at both ends and are designed for facile and accurate insertion into body vessels. Stents, as opposed to angioplasty balloons, are generally left in the vessels permanently, and reduce the chance of restenosis, i.e. reclosing or reblockage of the vessel, occurring, although stents may be temporarily placed in vessels as well.

Stents are also commonly used in other medical procedures as well including repair and support of injured tissue, in urological procedures (i.e. prostate surgery for holding open tracts of the urinary system), in reproductive surgeries, and so forth. Other commonly used devices include grafts and stent-grafts which serve similar purposes.

Various techniques are used in order to ensure accurate placement of the stent at the desired bodily location, and also to identify the position of the stent at some later date. It is critical to the success of the procedure that the stent does not shift from its position and consequently must be checked at various times after placement. One very common technique is to use a radiopaque material with the stent so that the stent image may be viewed using fluoroscopy. The stent may itself be produced from such a material, or various means may be utilized to attach a radiopaque material to a stent that itself does not otherwise fluoresce. This technique allows the stent to be rechecked at later dates using fluoroscopy.

There are some limitations to using such a technique, however. For instance, some types of materials such as tantalum, fluoresce so brightly that they obscure visibility of the lesion. Likewise, plating or coating the whole stent with a radiopaque material can result in the same effect. A further problem with coating or plating the entire stent with a radiopaque material is that it is more difficult to ascertain the orientation of the stent. For instance, some stents are placed at branches in a blood vessel. These stents are typically referred to as bifurcated stents, and are used where blockages occur at blood vessel junctions. A bifurcated stent is typically designed such that a second stent may be positioned through an opening in the bifurcated stent at a later date such that the stents together function to keep the branched blood vessel open to blood flow. It is particularly important in this instance to be able to readily ascertain where the opening of the bifurcated stent is to allow for accurate positioning of the second stent which is inserted later. If the entire stent is fluorescing, the opening of the stent as well as the blood vessel, may be obscured.

A further problem with the stent fluorescing or illuminating too brightly is that it makes it difficult for the person inserting the stent to accurately assess the stent length and diameter.

Another problem that may occur is that the addition of a radiopaque coating or layer to the stent can increase the rigidity of the stent and affect its expansion properties.

US 5725572 to Lam et al. describes a radiopaque marker that is affixed to portions of the undeformed components at least at the distal end and the proximal end of an intravascular stent so that the radiopaque material is visible under fluoroscopy and the distal stent end and the proximal stent end can be easily located in the body lumen where the stent is implanted. The patent describes plating a portion of the circumference of the stent or the entire circumference of the stent thereby producing a stent with a band of radiopaque material at its distal and proximal ends.

A need remains for a method of affixing radiopaque materials to only certain portions of a stent that overcomes the aforementioned problems.

SUMMARY OF THE INVENTION .

The present invention relates to an intraluminal device having radiopaque material selectively affixed thereon, and to methods of making the same.

The present invention further relates to a method of forming a radiopaque intraluminal device having a distal end, a proximal end, and a body having a center portion, the intraluminal device having a radiopaque material selectively affixed thereon comprising the steps of providing a preform in the form of a sheet or a tubes, optionally having a strut pattern formed therein, affixing at least one radiopaque material to said preform, and removing some of the radiopaque material from said preform in preselected areas by a process selected from laser cutting and chemical etching.

Where the preform is in the form of a sheet, the method further comprises the step of forming the preform into a tubular shape. The tubular shape can be retained by joining the edges of the sheet together and using a method of securing the edges together such as welding. A pattern, typically referred to as a strut pattern, may be formed in the preform either before of after affixing the radiopaque material. The strut pattern is formed by the removal of portions of the stent preform to form a patterned preform having radiopaque material selectively affixed to portions thereon. The formation of the strut pattern may be accomplished by laser cutting or etching, chemical etching, metal stamping, or by any other processes currently used to accomplish the removal.

The process of removing radiopaque material from the desired areas of the stent may be accomplished by laser cutting, chemical etching, metal stamping, and so forth.

Mechanical removal processes useful for removal of the radiopaque material from the desired areas also include microblasting and machine grinding, for instance. The radiopaque material can be completely removed from areas of the intraluminal device, or the method of the present invention can be used to vary the thickness of the radiopaque material over the surface of the stent. The result is that the stent is more illuminates more brightly in some areas than others. This can be extremely helpful for accurate placement of the device in an artery or vein.

The present invention also relates to an intraluminal device or stent formed by this process. Radiopaque material can be selectively and advantageously affixed to both bifurcated and nonbifurcated stents using the method of the present invention. This summary is not intended to limit the scope of the present invention.

Various embodiments of the present invention are discussed in the Detailed Description below.

BRIEF DESCRIPTION OF THE FIGURES Fig. 1 is a perspective view of an example of a bifurcated stent having a radiopaque coating selectively affixed to the distal end, proximal end, and a portion of the body of the stent.

Fig. 2 is a perspective view of a nonbifurcated stent in a tubular, unexpanded state having radiopaque coating selectively affixed to the proximal and distal ends of the stent.

Fig. 3 is a flat view of the same nonbifurcated stent as shown in fig. 2 having radiopaque material over the entire surface prior to selective removal of the radiopaque material from those areas where none is desired.

Fig. 4 is a perspective view of another non-bifurcated stent having radiopaque coating selectively affixed to the proximal and distal ends of the stent.

Fig. 5 is a flat view of the same stent shown in fig. 4 having radiopaque coating over the entire surface of the stent prior to selective removal of the radiopaque material from those areas where none is desired.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

While this invention may be embodied in many different forms, there are described in detail herein specific preferred embodiments of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated.

Generally, the intraluminal devices, or stents useful herein include tubular, flexible, expandable vascular or endoluminal stents adapted for deployment in a vessel or tract of a patient to maintain an open lumen. The stents are typically radially expandable stents formed from either a hollow tube or a sheet which may be polymeric, biocompatible metal, or metal-like materials with metal or metal-like materials being preferred. The stents have selectively affixed thereon, a radiopaque material to allow an operator to easily view the stents using fluoroscopy for accurate placement and positioning of the stent within an artery or vein. These radiopaque coatings are discussed in detail below.

Some examples of radial expandable stents useful herein are described generally in Application Serial Nos. 08/511 ,076; 09/111 ,531 ; and 09/197,276 all now pending, the entire contents of which are herein incorporated by reference. Other radial expandable stents are described generally in US 5807404, US 5836964 and US 5922005, the entire contents of which are herein incorporated by reference.

The stents typically have a multitude of openings in the stent wall, and are open at both the proximal and the distal end. These openings in the stent wall are pattern etched into the sheet or tube. This can be accomplished by laser etching or cutting, by chemical etching, by metal stamping, and so forth. This etching, cutting or stamping process therefore creates the stent strut pattern.

The stents are fabricated having a predetermined inner diameter in a production state and are adapted for expansion to a larger diameter upon deployment in a vessel or tract.

The method of the present invention is suitable for providing bifurcated stents with radiopaque coatings. A stent designed for placement at a branch in an artery or vessel may be referred to as a bifurcated stent. Sometimes the build-up of fatty substances or lesions that restrict the blood flow of an artery may form at the intersection between two arteries, that is, where the section where the two arteries form a generally "Y" shaped configuration (e.g. bifurcate, trifurcate, and so on).

Fig. 1 illustrates generally at 10 a particular embodiment of this type of stent. The stent has an opening 50 through which a second stent may be maneuvered and subsequently positioned at the branch. The two stents will therefore substantially form the " Y" shape at the obstructed intersection so that one stent may be placed in the first branch and the second stent may be placed in the second branch. The second stent may be placed in the vessel or artery during a subsequent procedure, or during the same procedure but following the placement and expansion of the first stent.

The stent therefore advantageously has a radiopaque coating 20, located at the distal end 60, at the proximal end 70 and around the opening 50. The distal end 60 has a smaller diameter than the proximal end 70, the distal end being inserted into the patient first. The stent can therefore not only be located, but the orientation of the stent may also be determined accurately using fluoroscopy. This is important for proper placement of the second stent through the opening of the first stent and into the branch of the vessel.

Fig. 2 illustrates a non-bifurcated stent of the type found in US Application Serial No. 08/511,076 incorporated by reference herein. As shown in fig. 2, a radiopaque coating 20 is affixed to each of the distal end 22 and the proximal end 24, actually interchangeable in this figure. Fig. 3 shows a flat view of the same stent as found in fig. 2, hereinafter referred to as a stent preform. The stent may be formed of a flat preform shown in fig. 2 that is formed into a tubular shape (fig. 1) by rolling the pattern so that it brings edges 12 and 14 together. Alternatively, the preform may already be a one piece tubular form that requires no rolling or welding. The edges may then be joined by welding or the like to provide a configuration such as that shown in fig. 2. The stent preform has been cut into a pattern of substantially parallel struts 16. Pairs of struts are interconnected at alternating end portions 19a and 19b. The radiopaque material 20 is shown over the entire surface of the patterned preform. As will be discussed in more detail below, the radiopaque material may be affixed to the preform either before or after strut pattern formation.

Fig. 4 shows generally at 30 a nonbifurcated stent of the type found in US 5807404, US 5836964 and US 5922005 incorporated by reference herein. As shown in fig. 4, a radiopaque coating 28, such as gold, is affixed to each of the distal end 32 and the proximal end 34, actually interchangeable in this figure. Struts 38 have been cut, etched, stamped, or so forth into the stent structure. Fig. 5 is a flat view of the same stent found in fig. 4 showing the general pattern of the stent which can be referred to as a stent preform. The preform may be rolled into a tubular shape (fig. 1) to bring the edges 42 and 44 together. Alternatively, the preform may already be a one piece tubular form having the strut pattern cut or etched into it. The tubular form thus requires no rolling or welding. The edges may then be joined by welding or the like to provide a configuration such as that shown in fig. 4. The stent preform has been cut into a pattern of substantially parallel struts 38. Pairs of struts are interconnected at alternating end portions 39a and 39b. The radiopaque material 40 is shown over the entire surface of the patterned preform. As will be discussed in more detail below, the radiopaque material may be affixed to the preform either before or after strut pattern formation.

The method of forming stents with radiopaque materials, or of affixing radiopaque coating to the stents of the present invention allows the radiopaque material to be accurately and conveniently placed in only those areas of the stent where the radiopaque material is desired. The radiopaque material may be affixed to a stent preform in either a sheet or tubular form. This may be done either before or after the strut pattern has been cut, etched or stamped in the preform. If a tubular preform is being used and the strut pattern has already been formed in the stent, this preform is basically a finished stent. All of these forms will, however, hereinafter be referred to as stent preforms. The stent preform may be in the form of a sheet or a tube, and may be made of various materials including polymeric materials, although in the present invention metals or metal-like materials are preferable for use. The stent may be formed of at least one metal, but may be comprised of more than one metal such as in the case of an alloy. Stent formation from such materials is well known to those of skill in the art. Biocompatible metals such as stainless steel, Nitinol (nickel-titanium alloys), and so forth.

Nitinol is discussed in US 6059810 herein incorporated by reference in its entirety. This patent refers to an article by L. McDonald Schetky for a discussion of such alloys entitled "Shape-Memory Alloys" at pp 74-82 of Volume 241 (5) November 1979, SCIENTIFIC AMERICAN, and to "A Source Manual For Information On Nitinol and Ni Ti", first revision, by David Goldstein, Research and Technology Department, Feb. 1, 5 1980, Naval Surface Weapons Center, Dalgren, Va. 22448 (NSWC TR 80-59), both of which are incorporated by reference herein.

Other alloys useful for stent formation, in addition to Nitinol, are discussed in US 5725570 herein incorporated by reference. This discussion includes stainless steel, as well as other superelastic materials including, e.g., silver-cadmium 0 (Ag-Cd), gold-Cadmium (Au-Cd), gold-copper-zinc (Au-Cu-Zn), copper-aluminum- nickel (Cu-Al-Ni), copper-gold-zinc (Cu-Au-Zn), copper-zinc/(Cu-Zn), copper-zinc- aluminum (Cu-Zn-Al), copper-zinc-tin (Cu-Zn-Sn), copper-zinc-xenon (Cu-Zn-Xe), iron-beryllium (Fe3-Be), iron-platinum (Fe3-Pt), indium-thallium (In-Tl), iron- manganese (Fe-Mn), nickel-titanium-vanadium ( i-Ti-V), iron-nickel-titanium-cobalt 5 (Fe-Ni-Ti-Co), and copper-tin (Cu-Sn). See also Schetsky, L. McDonald, "Shape

Memory Alloys", Encyclopedia of Chemical Technology (3rd ed.), John Wiley & Sons, 1982, vol. 20. pp. 726-736 for a full discussion of superelastic alloys, herein incorporated by reference. One method of affixing the radiopaque material to the stent preform is by electroplating the sheet or tubular preform with the radiopaque material. 0 This may be accomplished by dipping the sheet or tubular member in the electroplating solution. At this point, the entire surface of the sheet or tube is coated with the radiopaque material. There are optional steps that may be undertaken during the electroplating process. This can improve the adhesion of the radiopaque material to the stent in those situations where good adhesion may be difficult to achieve. 5 A first optional step which may be referred to in the industry as acid etching involves the placement of the metal sheet or tube in an acid bath prior to electroplating to remove oxides from the surface of the metal. The use of this technique is known to one of skill in the art and is sometimes referred to as "pickling." This may be accomplished out of a sulfuric acid bath, for instance. The metal is typically rinsed 0 both prior to and after the acid etching step.

A second optional step involves application to the metal tube or sheet of what is referred to as a "strike" layer. The strike layer is a very thin electrochemically deposited layer that prevents reformation of oxides on the surface of the metal thereby improving the adhesion of the subsequent coating.

During the strike, the metal is plated with a solution of a metal salt wherein a thin layer of metal, i.e. the "strike", is immediately deposited on the surface of the metal sheet or tube. This layer is controlled by the concentration of the solution, the time of exposure, and the amperage of the current, to a thickness of preferably about 5 x 10"6 cm to about 1.5 x 10"5 cm (about 0.5 μm to about 1.5μm; about 500 to about 1500 A). A typical strike layer is approximately 1.3 x 10"5 cm (about 1.3 μm or 1270 Λ). This thin layer has no affect on the rigidity or expansion properties of the stent thereby allowing the entire surface to be coated with a simple immersion step. The "strike" layer may be optionally added to improve the adhesion of the subsequently applied radiopaque coating to the metal.

The very thin "strike" layer allows the entire metal sheet or tube to be dipped in a plating solution of the metal because the thin coating will not have an adverse affect on the stent properties, such as decreased flexibility or increased radiopacity. The strike layer may be comprised of any metal typically used for a "strike" including any of the noble metals such as gold, silver, nickel, and so forth. A gold "strike" is desirable. Gold has been found to be a preferable choice because it tends to cause less thrombus, tissue irritation and/or allergic reaction and so forth than other metals such as nickel, for instance.

The sheet or tube may then be electroplated with the desired radiopaque material. The present invention allows for a simplistic electroplating method because the entire metal form may be immersed in the electroplating solution. Electroplating methods are well known to those of ordinary skill in the art.

Any radiopaque material may be used in the present invention including the noble metals such as gold, platinum, tantalum, rhenium and iridium, and the non- noble metal, silver. Radiopaque materials useful for providing stents with radiopacity are discussed in US 5725570 herein incorporated by reference in its entirety. Some metals, such as tantalum, irradiate more brightly than others and the metal can therefore be selected on such basis. Some particular embodiments of the present invention utilize gold as the metal of choice. Gold is useful due to its nonallergenic qualities, as well as its radiopacity.

Again, as noted above, gold is a desirable choice because it is known to produce less thrombus, tissue irritation and/or allergic reaction. The thickness of the coating may be varied, but is preferably between about 1 μm to about 20 μm (about 3.9 x 10"5 inches to about 7.9 x 10"4 inches), preferably from about 2 μm to about 12μm (about 7.9 x 10"5 inches to about 4.7 x 10"4 inches). The desired thickness may be achieved, for instance, through one or more electrochemical depositions. The coating thickness can be varied over the surface of the stent in order to vary the radiopacity over the surface of the stent. It may be desirable to coat some areas thicker than others to increase the irradiation in those areas where the radiopaque material is coated thicker. This variation in thickness can be controlled by how much material is plated on the surface, as well as by the removal process itself. For instance, etching can be used to remove more radiopaque coating from some areas than others therefore controlling the coating thickness in this manner.

Further, different radiopaque materials can be coated on different portions of the stent to vary the radiopacity of the stent as well. For instance, tantalum can be coated on one portion and gold on another portion. The tantalum will irradiate more brightly than the gold. For example, in a bifurcated stent, it may be desirable to mark the opening in the stent with tantalum so that it illuminates more brightly. Or, it may be desirable that only the ends of the stent are clearly visible, and consequently, it may be desirable to mark the ends so that they illuminate brightly, and to mark the center portion so that it is only slightly radiopaque. Using the method of the present invention, selective marking of the stents is easily accomplished.

The ability to control how much coating is located on various parts of the stent is extremely helpful for accurate placement of the stent in a body lumen. For a bifurcated stent, for instance, it may be desirable that the proximal and distal ends of the stent are radiopaque, as well as the portion of the stent surrounding the opening, i.e. the bifurcation, where the second stent is to be placed as is shown in Fig. 1. This type of pattern allows for an easy determination as to stent orientation and position, as well as the length and diameter of the stent. The position of the stent is particularly critical for bifurcated stents because it is necessary that the operator can accurately determine if the opening of the stent is matched with the branch in the artery or vessel. For this reason, it may be desirable that the opening in the center illuminate more brightly so that the operator who is positioning the stent can accurately place the opening at the branch in the artery. Furthermore, when placing the second stent through the opening, the operator will be able to accurately ascertain where the opening easy for easier stent placement.

In the case of nonbifurcated stents, it may be desirable that only the ends illuminate, or that the ends illuminate more brightly so that the proper position and orientation of the stent may be determined not only during insertion, but also at later dates to determine if the stent position has changed as shown in Figs. 2 and 3.

A strut pattern may be formed in the stent preform either before or after the electroplating process. The strut pattern is formed by laser cutting or etching, chemical etching, metal stamping, and so forth. Following the formation of the strut pattern, the gold plating or coating may then be removed from those areas where it is desired that the stent be non-radiopaque, consequently leaving the gold coating on those areas of the stent where radiopacity is desired. This may also be accomplished using an etching process, either laser or chemical etching processes may be used. This process is therefore used to remove the radiopaque material from certain areas of the stent preform. If it is a metal sheet that has been electroplated and etched, it will then be necessary to form the sheet into a tube, and to join the tube together at the seam.

There are various advantages to using the method of the present invention. One advantage is that it simplifies the production process. The selective etching method of the present invention eliminates the need for premasking of the stent prior to plating. Furthermore, using this method of plating only portions of the stent eliminates wash out or haloing. These phenomena can occur where the whole stent is either itself formed of a radiopaque material, such as tantalum, or the entire stent is coated with a relatively thick layer of a radiopaque material. This makes the stent difficult to view under fluoroscopy because it illuminates too brightly, making the lines of the stent indistinct, and not clearly discernible. Furthermore, it makes it difficult to accurately determine the location and orientation of the stent. Also, if the stent is very luminous, the haloing can obscure visibility of the blood vessel lesion, and can actually mask it, making it difficult to repair the vessel.

Further to the present invention, selective plating allows the expansion characteristics of the stent to be controlled. For instance, application of the coating layer in certain areas can increase the rigidity of the stent in those areas. This can result in either a "watermelon seed" effect wherein the stent shoots from the desired location of stent placement, or if the middle deploys first, the stent may lodge in the vessel. It has been noted that the coating can increase the rigidity of the stent in those areas where it is plated. This fact must be taken into account because it can change the method by which the stent opens. For instance, the balloon may open the center or body of the stent first if the end portions are plated but not the center. However, controlling the mode of deployment wherein the ends or center portion open first may be desirable in some cases. The thicker the coating, the more likely that the stent may deploy first at those portions where the coating is not as thick. With the method of the present invention, the stent can be balanced easily by selectively plating certain areas, thereby preventing undesirable movement of the stent. For instance, if a portion of the middle of the stent is plated, as well as the distal and proximal ends, the center will have less of a tendency to open first. Furthermore, the thickness to which the areas are plated can be easily controlled. For instance, certain portions of the stent may be plated with a thicker coating, causing the stent to illuminate more brightly in certain areas. This would allow not only the location of the stent to be easily determined, but the orientation of the stent as well.

The current invention allows the use of a base stainless steel stent which maintains good flexibility. The application of the radiopaque material to only the ends or specified subsections does not increase stent rigidity. In addition to being directed to the embodiments described above and claimed below, the present invention is further directed to embodiments having different combinations of the features described above and claimed below. As such, the invention is also directed to other embodiments having any other possible combination of the dependent features claimed below. The above figures and disclosure are intended to be illustrative and not exhaustive, and will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims attached hereto. While the embodiments discussed above have focused to a large degree on stents, other implantable medical devices may be treated using the method of the present invention without detouring from the spirit of the present invention.

The contents of parent application No . 09/659 ,571 , filed September12 , 2000 , is incorporated herein by reference in its entirety .

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
WO2004004966A1 *18 Jun 200315 Jan 2004Boston Scientific LimitedLaser/fluid jet cutting process and system
US68880989 Jan 20043 May 2005Scimed Life Systems, Inc.Tubular cutting process and system
US91800327 Jul 200810 Nov 2015Boston Scientific Scimed, Inc.Tubular cutting process and system
Classifications
International ClassificationA61F2/91, A61F2/915, A61F2/856, A61F2/00, A61B19/00
Cooperative ClassificationA61F2002/91541, A61F2/91, A61B90/39, A61F2/856, A61F2/915, A61F2002/91558, A61F2250/0098
European ClassificationA61F2/91, A61F2/915, A61F2/856
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