Polymeric marker with high radiopacity

Abstract

High radiopacity is achieved in a polymeric marker by combining a polymeric resin, a powdered radiopaque agent having uniformly shaped particles of a specific particle size distribution and a vetting agent. The method to produce the marker calls for the blending and pelletization of these materials followed by extrusion onto support beading. The resulting supported tubing is subsequently cut to length with the beading still in place. After ejection of the beading remnant the marker is slipped into place on the device to be marked and attached by melt bonding. Marking of a guidewire allows lesions to be measured while the marking of balloon catheters allow the balloon to be properly positioned relative to a lesion.

Description

BACKGROUND OF THE INVENTION [0001] The present invention is directed to elongated intracorporeal devices, and more particularly intraluminal devices for stent deployment, percutaneous transluminal coronary angioplasty (PTCA), and the similar procedures. PTCA is a widely used procedure for the treatment of coronary heart disease. In this procedure, a balloon dilatation catheter is advanced into the patient's coronary artery and the balloon on the catheter is inflated within the stenotic region of the patient's artery to open up the arterial passageway and increase the blood flow through the artery. To facilitate the advancement of the dilatation catheter into the patient's coronary artery, a guiding catheter having a preshaped distal tip is first percutaneously introduced into the cardiovascular system of a patient by the Seldinger technique through the brachial or femoral arteries. The catheter is advanced therein until the preshaped distal tip of the guiding catheter is disposed wi...

AI Technical Summary

Benefits of technology

[0008] The present invention overcomes the shortcomings of previously described polymeric radiopaque markers by enabling a polymer to be filled or doped with a considerably greater quantity of a radiopaque agent than has heretofore been achievable. The increased fill ratio nonetheless allows uniform pellets to be compounded and an extrusion with the appropriate wall thickness to be formed. The resulting marker provides an unprecedented combination of radiopacity and flexibility. Such marker would allow any of various intraluminal devices to be radiopaquely marked including, but not limited to, coronary, peripheral, and guiding catheters as well as guidewires.

[0010] While previous attempts to increase fill ratios have involved tungsten powder of relatively fine particle size, the present invention relies on the use of particles of increased size in order to achieve such end. An increase in particle size has been found to allow the polymer to more effectively function as a continuous binder and thereby increase ductility at a given fill ratio or maintain ductility at increased fill ratios. It has been found that in constraining the average particle size to at least 2 microns and limiting maximum particle size to about 20 microns provides the desired results. In the case of tungsten in Pebax, a fill ratio of about 91.3 weight percent (equivalent to 36.4 volume percent) is readily attainable. Additionally, it has been found that the process by which the tungsten powder is produced has a considerable effect on both particle size distribution as well as the shape of the individual particles. Tungsten powder produced by either a “pusher” process or “atomization” process, then milled and classified has been found to provide discrete particles having a more equiaxed shape and size respectively and are therefore more ideally suited for the purposes of the present invention than powders produced employing a “rotary” process.

[0012] Due to its high radiopacity, flexibility and melt bondability, the marker of the present invention is readily attached to for example the inner member of a balloon catheter, a guidewire, and even a guide catheter tip. The attachment of radiopaque markers of known dimensions to a guidewire or the attachment to a guidewire of multiple radiopaque markers with known separation distances impart a measurement capability to the catheter that allows a physician to quickly and easily measure lesions and decide on appropriate stent lengths.

Problems solved by technology

Such configuration, however, locally stiffens the catheter shaft and thereby imparts an undesirable discontinuity thereto as the solid metal bands are relatively inflexible compared to a polymer balloon catheter shaft.

Additionally, the metallic markers are relatively expensive to manufacture and relatively difficult to positively affix to an underlying device.

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