Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
1998-04-20
2001-09-25
Prebilic, Paul B. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
C623S001340, C606S198000
Reexamination Certificate
active
06293966
ABSTRACT:
FIELD OF THE INVENTION
The following invention relates to stents for implantation into a body lumen, such as an artery, which are radially expandable. More specifically, this invention relates to radially expandable surgical stents which are provided with radiopaque markers thereon to enhance their visibility when viewed with an imaging device such as a fluoroscope.
BACKGROUND OF THE INVENTION
Surgical stents have long been known which can be surgically implanted into a body lumen, such as an artery, to reinforce, support, repair or otherwise enhance the performance of the lumen. For instance, in cardiovascular surgery it is often desirable to place a stent in the coronary artery at a location where the artery is damaged or is susceptible to collapse. The stent, once in place, reinforces that portion of the artery allowing normal blood flow to occur through the artery. One form of stent which is particularly desirable for implantation in arteries and other body lumens is a cylindrical stent which can be radially expanded from a first smaller diameter to a second larger diameter. Such radially expandable stents can be inserted into the artery by being located on a catheter and fed internally through the arterial pathways of the patient until the unexpanded stent is located where desired. The catheter is fitted with a balloon or other expansion mechanism which exerts a radial pressure outward on the stent causing the stent to expand radially to a larger diameter. Such expandable stents exhibit sufficient rigidity after being expanded that they will remain expanded after the catheter has been removed.
Radially expandable stents come in a variety of different configurations to provide optimal performance in various different particular circumstances. For instance, the United States patents to Lau (U.S. Pat. Nos. 5,514,154, 5,421,955, and 5,242,399), Baracci (U.S. Pat. No. 5,531,741), Gaterud (U.S. Pat. No. 5,522,882), Gianturco (U.S. Pat. Nos. 5,507,771 and 5,314,444), Termin (U.S. Pat. No. 5,496,277), Lane (U.S. Pat. No. 5,494,029), Maeda (U.S. Pat. No. 5,507,767), Marin (U.S. Pat. No. 5,443,477), Khosravi (U.S. Pat. No. 5,441,515), Jessen (U.S. Pat. No. 5,425,739), Hickle (U.S. Pat. No. 5,139,480), Schatz (U.S. Pat. No. 5,195,984), Fordenbacher (U.S. Pat. No. 5,549,662) and Wiktor (U.S. Pat. No. 5,133,732), each include some form of radially expandable stent for implantation into a body lumen.
One problem encountered in the use of radially expandable surgical stents is the difficulty in precisely determining the position of the stent both before, during and after it is implanted and expanded. Typically, stents are formed from stainless steel or a nickel titanium alloy. These materials are not readily perceptible when medical imaging devices, such as fluoroscopes are used to view the site where the stent has been implanted. To enhance the radiopacity of surgical stents, it is known in the prior art to provide a radiopaque marker on the stent which is clearly identifiable when a fluoroscope or other imaging device is used. Such radiopaque stents taught in the prior art have suffered from a number of drawbacks. For instance, many radiopaque markers restrict the ability of the stent to expand radially, protrude from the surface of the stent in a potentially harmful manner, fail to provide a complete outline of the extent of the stent, or illuminate so brightly on an imaging device that fine details such as blood vessels and other bodily structures are obscured in the images obtained.
One such radiopaque marker stent is the subject of European Patent Application No. 95302708.3 published on Nov. 2, 1995. The radiopaque stent markers identified in this European patent application utilize plating techniques to plate a band of radiopaque material to portions of the radially expandable stent. The radiopaque stent markers disclosed in this European patent application significantly enlarge the thicknesses of the elements adjacent where the plating occurs, making this technique significantly less effective on stents sized for implantation in smaller body lumens. If a lesser plating thickness is utilized, insufficient radiopaque material is added to provide the desired radiopacity. Other drawbacks of the radiopaque stent markers of this European patent application include that the plating material can become detached from the stent, especially when the plating material is gold and the stent is made of stainless steel. Also, such plated stents must be masked on both outer and inner surfaces. The masking procedure is difficult to accurately perform, especially on inner surfaces of stents with small diameters.
Accordingly, a need exists for a radially expandable stent featuring radiopaque markers which can be utilized on stents of all different sizes, does not interfere with the expansion of the stent and provides a clear image on a fluoroscope or other medical imaging device. Such a stent with radiopaque markers should additionally be configured in a manner facilitating its manufacture using known manufacturing techniques and commonly utilized implantation materials.
SUMMARY OF THE INVENTION
This invention provides radiopaque marker elements for attachment to radially expandable surgical stents. Separate marker elements are attached to ends of the stent which allow the ends of the stent to be readily viewable by a fluoroscope or other imaging device. The marker elements are formed of a homogeneous material having radiopaque characteristics, rather than merely having a surface of radiopaque material overlying other non-radiopaque elements of the stent.
Each marker element is mechanically attached to an end of the stent with an axial center of the marker element coextensive with a central axis of the stent. The marker element is configured to be radially expandable in a manner similar to the radial expansion of the stent itself. Thus, the presence of the marker element adjacent an end or ends of the stent does not in any way inhibit the radial expansion of the stent within a body lumen during use. The marker elements are attached to the ends of the stent in positions beyond the ends of the stent so that when a marker element is attached to both ends of the stent, the stent can be viewed with an imaging device, such as a fluoroscope, and the maximum extent and precise position of the stent can be accurately determined. The marker elements can either be circumferentially continuous, completely circumscribing the central axis of the stent, or discontinuous with a series of disconnected marker elements secured to the ends of the stent at separate positions thereon.
In a preferred form of the invention, the marker elements have a circumferential contour which mirrors a contour of other circumferential elements forming the cylindrical radially expandable stent. In this way, such circumferential marker elements provide a geometric structure and expansion characteristics to the stent which mirror those of other portions of the stent and do not alter performance of the stent.
The marker elements can either be located directly adjacent the ends of the stent in a manner only slightly increasing a length of the stent or the marker elements can be spaced from the adjacent portions of the stent in a manner causing the marker elements to enhance somewhat the overall length of the stent. With the radiopaque marker elements in place attached to the ends of the stent, the location and orientation of the stent can be precisely determined both before, during and after implantation and radial expansion of the surgical stent within the body lumen.
OBJECTS OF INVENTION
Accordingly, a primary object of the present invention is to provide a radially expandable surgical stent which features radiopaque marker elements attached thereto which enhance visibility of the stent when viewed through a fluoroscope or other imaging device.
Another object of the present invention is to provide a radially expandable surgical stent with radiopaque marker elements that do not inhibit radial expansion and support of a body lumen by havi
Cook Incorporated
Godlewski Richard J.
Ness Anton P.
Prebilic Paul B.
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