Radiopaque nitinol alloys for medical devices

Abstract

A radiopaque nitinol medical device such as a stent for use with or implantation in a body lumen is disclosed. The stent is made from a superelastic alloy such as nickel-titanium or nitinol, and includes a ternary element selected from the group of chemical elements consisting of iridium, platinum, gold, rhenium, tungsten, palladium, rhodium, tantalum, silver, ruthenium, or hafnium. The added ternary element improves the radiopacity of the nitinol stent comparable to that of a stainless steel stent of the same size and strut pattern coated with a thin layer of gold. The nitinol stent has improved radiopacity yet retains its superelastic and shape memory behavior and further maintains a thin strut/wall thickness for high flexibility.

1 . A radiopaque medical device for use in a body lumen, comprising: 
 a tubular-shaped body having a thin wall defining a strut pattern;    wherein the body includes a superelastic alloy, and the alloy further includes a ternary element selected from the group of chemical elements consisting of iridium, platinum, rhenium, palladium, rhodium, silver, and ruthenium;    wherein an atomic percent of the ternary element is greater than 3 percent and less than or equal to 10 percent; and    wherein the medical device exhibits a level of radiopacity.    
     
     
         2 . The radiopaque medical device of  claim 1 , wherein the thin wall is at least 10 percent thinner than an identically-shaped and sized medical device having the same level of radiopacity.  
     
     
         3 . The radiopaque medical device of  claim 1 , wherein the strut pattern has a cross-sectional area that is 10 percent smaller than a cross-sectional area of a strut of an identically-shaped and sized medical device having the same level of radiopacity.  
     
     
         4 . The radiopaque medical device of  claim 1 , wherein the superelastic alloy includes a nickel-titanium alloy.  
     
     
         5 . The radiopaque medical device of  claim 4 , wherein the atomic percent of titanium is greater than or equal to about 46 and less than or equal to about 52.  
     
     
         6 . The radiopaque medical device of  claim 1 , wherein an austenite finish temperature (A f ) of the superelastic alloy in the medical device is greater than or equal to zero and less than or equal to 37 degrees C.  
     
     
         7 . The radiopaque medical device of  claim 1 , wherein the tubular-shaped body includes raw tubing having an austenite finish temperature (A f ) of greater than or equal to about −15 degrees C. and less than or equal to about 15 degrees C.  
     
     
         8 . A superelastic, radiopaque metallic stent for medical applications, comprising: 
 a tubular-shaped body having a thin wall defining a strut pattern;    wherein the body includes a superelastic nickel-titanium alloy and the alloy further includes a third element selected from the group of chemical elements consisting of iridium, platinum, rhenium, palladium, rhodium, silver, and ruthenium such that an atomic percent of the ternary element is greater than 3 percent and less than or equal to 10 percent; and    wherein the stent exhibits a level of radiopacity.    
     
     
         9 . The superelastic, radiopaque metallic stent of  claim 8 , wherein the radiopacity of the stent is substantially equivalent to a 316L stainless steel stent having an identical strut pattern and size and coated with about 2.7 to about 6.5 μm of gold.  
     
     
         10 . The superelastic, radiopaque metallic stent of  claim 8 , wherein the atomic percent of platinum is about 7.5.  
     
     
         11 . The superelastic, radiopaque metallic stent of  claim 8 , wherein the strut pattern is laser cut from a tube.  
     
     
         12 . A radiopaque medical device for use in a body lumen, comprising: 
 a self-expanding body, wherein the body includes a superelastic nickel-titanium alloy;    wherein the nickel-titanium alloy includes a radiopacity enhancing ternary element selected from the group consisting of palladium and platinum such that an atomic percent of palladium is greater than 3 percent and less than or equal to 20 percent and an atomic percent of platinum is greater than 3 percent and less than or equal to 15 percent; and    wherein the medical device exhibits a level of radiopacity greater than the nickel-titanium alloy without the radiopacity enhancing ternary element.    
     
     
         13 . A radiopaque medical device for use in a body lumen, comprising: 
 a self-expanding cylindrical body, wherein the body includes a superelastic nickel-titanium alloy;    wherein the nickel-titanium alloy includes a radiopacity enhancing ternary element selected from the group of chemical elements consisting of iridium, platinum, rhenium, palladium, rhodium, silver, and ruthenium wherein an atomic percent of the ternary element is greater than 3 percent and less than or equal to 10 percent; and    wherein the medical device exhibits a level of radiopacity greater than the nickel-titanium alloy without the radiopacity enhancing ternary element.    
     
     
         14 . A radiopaque medical device for use in a body lumen, comprising: 
 a self-expanding body, wherein the body includes a superelastic nickel-titanium alloy;    wherein the nickel-titanium alloy includes a radiopacity enhancing ternary element including platinum having an atomic percent greater than 3 percent and less than or equal to 15 percent; and    wherein the medical device exhibits a level of radiopacity greater than binary nickel-titanium.    
     
     
         15 . A method for providing a radiopaque medical device, comprising: 
 providing a self-expanding tubular body made from a superelastic nickel-titanium alloy, wherein the nickel-titanium alloy includes a radiopacity enhancing ternary element selected from the group consisting of palladium and platinum such that an atomic percent of palladium is greater than 3 percent and less than or equal to 20 percent and an atomic percent of platinum is greater than 3 percent and less than or equal to 15 percent;    cutting a strut pattern into the tubular body;    heat treating the tubular body; and    wherein the medical device exhibits a level of radiopacity greater than the nickel-titanium alloy without the radiopacity enhancing ternary element.    
     
     
         16 . A method for providing radiopaque tubing, comprising: 
 forming a tubular-shaped body having a thin wall, wherein the body includes a superelastic nickel-titanium alloy and the alloy further includes a ternary element selected from the group of chemical elements consisting of iridium, platinum, gold, rhenium, tungsten, palladium, rhodium, tantalum, silver, ruthenium, and hafnium; wherein the step of providing a tubular-shaped body includes melting nickel, titanium, and the ternary element, cooling to form an alloy ingot, hot forming the alloy ingot, forming the alloy ingot into a cylinder, drilling the cylinder to form tubing, drawing the tubing, and annealing the tubing.    
     
     
         17 . The method of  claim 16 , wherein the atomic percent of platinum is greater than 3 and less than or equal to 15.  
     
     
         18 . The method of  claim 16 , wherein the atomic percent of palladium is greater than 3 and less than or equal to 20.