Double-butted superelastic nitinol tubing

Abstract

A medical device such as a stent made from single or double-butted tubing is disclosed. The butted tubing may be made from stainless steel or a nickel-titanium (nitinol) alloy. The butted tubing is created by thinning the material in between the ends of the tube through machining, drawing, cold working, laser cutting, or chemical etching. A strut pattern for a stent is laser cut into the butted tubing. The strut pattern for the stent includes rings connected by links. The end rings of the stent coincide with the double-butted ends of the tubing thereby increasing the hoop strength of those end rings.

1 . Tubing for a medical device, comprising: 
 a body having a tubular shape with opposite ends, wherein at least one of the ends is butted with material built up radially inward creating a greater wall thickness at that location while maintaining a constant outside diameter along a length of the tubular shape;    wherein the body includes a nickel-titanium alloy that deforms superelastically.    
   
   
       2 . The tubing of  claim 1 , wherein both ends of the tubular shape are butted.  
   
   
       3 . The tubing of  claim 1 , wherein the butted end is created by a material removal process selected from the group of processes consisting of: electric discharge machining, laser beam cutting, or chemical etching.  
   
   
       4 . The tubing of  claim 1 , wherein the body includes butting at about a mid-section thereof.  
   
   
       5 . The tubing of  claim 1 , wherein the butted end is formed by removing material in a wall thickness adjacent to the butted end.  
   
   
       6 . The tubing of  claim 1 , wherein the opposite ends are butted and the butted ends have different wall thicknesses.  
   
   
       7 . Tubing for an implantable stent for use in a body lumen, comprising: 
 a self-expanding body having a tubular shape with at least one butted end with material locally built up to extend radially inward increasing the wall thickness while maintaining a constant outside diameter along a length of the tubular shape;    wherein the body includes a nickel-titanium alloy that is superelastic inside the body lumen.    
   
   
       8 . The tubing of  claim 7 , wherein the body has two butted ends each having different lengths.  
   
   
       9 . The tubing of  claim 7 , wherein the body has two butted ends and the butted ends are formed by removal of material in a section in between the butted ends.  
   
   
       10 . The tubing of  claim 7 , wherein a transition temperature of the nickel-titanium alloy is set at one of approximately 37 degrees C. and below approximately 37 degrees C.  
   
   
       11 . A method for fabricating tubing for a medical device, comprising: 
 providing a body having a tubular shape with opposite ends made from a nickel-titanium alloy that is superelastic when stressed; and    forming a butted end at one of the ends by building up material radially inward thereby locally increasing the wall thickness while maintaining a constant outside diameter along a length of the tubular shape.    
   
   
       12 . The method of  claim 11 , wherein the step of forming a butted end includes thinning a wall thickness adjacent to the butted end by removing material.  
   
   
       13 . The method of  claim 11 , wherein the step of forming a butted end includes thinning a wall thickness adjacent to the butted end by cold work.  
   
   
       14 . The method of  claim 11 , wherein the step of forming a butted end includes thinning a wall thickness adjacent to the butted end by drawing.  
   
   
       15 . The method of  claim 11 , wherein the method further comprises forming a second butted end at the opposite end.  
   
   
       16 . The method of  claim 11 , wherein the butted end is created by a material removal process selected from the group of processes consisting of: electric discharge machining, laser beam cutting, or chemical etching.  
   
   
       17 . The method of  claim 11 , wherein the method further comprises providing a length of stock tubing, forming a plurality of butting along a length thereof, and cutting the stock tubing into multiple pieces.  
   
   
       18 . Tubing for a medical device application, comprising: 
 a tubular shape body having a mid-section and opposite ends including a nickel-titanium alloy that deforms superelastically;    butting formed in an interior of the tubular shape body within the mid-section thereof with material built up radically inward thereby increasing the wall thickness locally while maintaining a constant outside diameter along a length of the tubular shape body; and    a pattern with openings formed into the tubular shape body.    
   
   
       19 . The tubing of the  claim 18 , wherein the tubing includes butting at an end of the tubular shape body.