Polymeric marker with high radiopacity for use in medical devices
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 wetting 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.
1. A radiopaque marker which is secured to a medical device, and which is a circular band having a length greater than a wall thickness of the marker, comprising:
a) a polymer;
b) radiopaque particles disposed within said polymer, comprisiong about 90.8 to about 93.2 weight percent of the marker, and having an average diameter of at least 2 microns and a maximum diameter of about 20 microns; and
c) a wetting agent for facilitating encapsulation of said particles by said polymer, and wherein the marker band has a radiopacity that is substantially constant along the length of the marker band, and a double wall thickness that varies by less than 0.001 inches along the entire length of the marker band.
2. The radiopaque marker of claim 1 , wherein said radiopaque particles comprise greater than 18 volume percent of said marker.
3. The radiopaque marker of claim 2 , wherein said radiopaque particles comprise approximately 36 volume percent of said marker.
4. The radiopaque marker of claim 1 , wherein said polymer comprises polyether block amide and said radiopaque particles comprise tungsten powder.
5. The radiopaque marker of claim 4 , wherein said wetting agent comprises maleic anhydride graft polyolefin.
6. The radiopaque marker of claim 1 , wherein said radiopaque particles are substantially equiaxed.
7. The radiopaque marker of claim 6 , wherein said particles are produced by a pusher process.
8. The radiopaque marker of claim 6 , wherein said particles are produced by an atomization process, resulting in a substantially spherical particle.
9. The radiopaque marker of claim 1 , further comprising an antioxidant.
10. The radiopaque marker of claim 1 , wherein said polymer is thermoplastic.
11. The radiopaque marker of claim 1 wherein the radiopaque particles comprise about 34.9 to about 42.7 volume percent of the marker.
12. The radiopaque marker of claim 1 wherein the marker is secured to the medical device with an adhesive.
13. The radiopaque marker of claim 1 wherein the double wall thickness of the marker is about 0.005 inches and varies by about 0.0005 inches.