Thermoelastic and superelastic Ni-Ti-W alloy

• US 7,658,760 B2
• Filed: 08/13/2004
• Issued: 02/09/2010
• Est. Priority Date: 12/28/2000
• Status: Expired due to Fees

• Current Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories Incorporated)
• Inventors: Pelton, Brian Lee, Boylan, John F.
• Primary Examiner(s): SWEET, THOMAS
• Application Number:
  US10/917,701
• Publication Number:
  US 20050021129A1
• Time in Patent Office: 2,006 Days
• Field of Search: 623/1.15, 623/1.19, 623/1.34
• US Class Current: 623/1.19
• CPC Class Codes: A61F 2/82 Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents stent-grafts for tubular structures of the body other than blood vessels A61F2/04; stent-grafts for blood vessels A61F2/07; instruments specially adapted for placement or removal of stents or stent-grafts A61F2/95; for closing wounds, or holding wounds closed A61B17/04 - A61B17/115; dilators A61M29/00
• CPC Class Codes: A61F 2/90 characterised by a net-like or mesh-like structure
• CPC Class Codes: A61F 2/91 made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes
• CPC Class Codes: A61F 2/915 with bands having a meander structure, adjacent bands being connected to each other
• CPC Class Codes: A61F 2/962 having an outer sleeve
• CPC Class Codes: A61F 2002/91516 the meander having a change in frequency along the band
• CPC Class Codes: A61F 2002/91533 characterised by the phase between adjacent bands
• CPC Class Codes: A61F 2002/91575 connected peak to trough
• CPC Class Codes: A61F 2210/0019 operated at only one temperature whilst inside or touching the human body, e.g. constrained in a non-operative shape during surgery, another temperature only occurring before the operation
• CPC Class Codes: A61F 2230/0013 Horseshoe-shaped, e.g. crescent-shaped, C-shaped, U-shaped
• CPC Class Codes: A61L 2400/16 Materials with shape-memory or superelastic properties
• CPC Class Codes: A61L 31/022 Metals or alloys
• CPC Class Codes: A61L 31/14 Materials characterised by their function or physical properties , e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
• CPC Class Codes: A61L 31/18 Materials at least partially X-ray or laser opaque
• CPC Class Codes: C22C 19/03 based on nickel
• CPC Class Codes: C22F 1/006 Resulting in heat recoverable alloys with a memory effect
• CPC Class Codes: Y10S 623/90 Stent for heart valve
• CPC Class Codes: Y10S 623/901 Method of manufacturing prosthetic device

Abstract

A radiopaque nitinol stent for 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 including tungsten. The added tungsten in specified amounts improve the radiopacity of the nitinol stent comparable to that of a stainless steel stent of the same strut pattern coated with a thin layer of gold. Furthermore, 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.

Claims

1. Radiopaque tubing, comprising:

a tubular-shaped body wherein the body includes a nickel-titanium superelastic alloy with a ternary element including tungsten, said alloy exhibiting a stress-strain curve that approximates the idealized stress-strain curve of binary nickel-titanium,

wherein the body is radiopaque and the tubular-shaped body includes a strut pattern with struts no greater than 0.0046 inch in width.

2. The radiopaque tubing of claim 1, wherein the atomic percent of the tungsten greater than or equal to 5 and less than or equal to 12.

3. The radiopaque tubing of claim 1, wherein the atomic percent of the nickel is approximately 50.8, the atomic percent of the titanium is approximately 40, and the atomic percent of the tungsten is approximately 10.

4. The radiopaque tubing of claim 1, wherein the superelastic alloy includes a stress-induced martensite phase.

5. The radiopaque tubing of claim 1, wherein the atomic percent of the nickel is approximately 50.8, the atomic percent of the titanium is a maximum of approximately 40, and the atomic percent of the tungsten is approximately 10.

6. The radiopaque tubing of claim 1, wherein the superelastic alloy in the tubing with said strut pattern has an austenite finish temperature (A_f) of greater than or equal to zero and less than or equal to 30 degrees C.

7. The radiopaque tubing of claim 1, wherein the tubular-shaped body includes raw tubing having an austenite finish temperature (A_f) of greater than or equal to −

15 degrees C. and less than or equal to 0 degrees C.

17. The radiopaque tubing of claim 1, wherein the tubular-shaped body is formed from a nickel-titanium-tungsten tubing having an austenite finish temperature ranging from −

15°

C. to 0°

C.

8. A superelastic, radiopaque metallic tubing for medical applications, comprising:

a tubular-shaped body, wherein the body includes a superelastic nickel-titanium alloy and the alloy further includes tungsten, said alloy exhibiting a stress-strain curve that approximates the idealized stress-strain curve of binary nickel-titanium;

wherein the tubular-shaped body is formed from a nickel-titanium-tungsten tubing that has undergone cold forming and heat treating and the tubular-shaped body includes a strut pattern with struts no greater than 0.0046 inch in width.

9. The superelastic, radiopaque metallic tubing of claim 8, wherein the atomic percent of the nickel is approximately 50.8, the atomic percent of the titanium is a maximum of approximately 40, and the atomic percent of the tungsten is approximately 10.

10. The superelastic, radiopaque metallic tubing of claim 8, wherein the atomic percent of the tungsten greater than or equal to 5 and less than or equal to 12.

11. The superelastic, radiopaque metallic tubing of claim 8, wherein the tubing includes a strut pattern having struts and each strut has a cross-sectional area of less than 0.000021 in².

12. The superelastic, radiopaque metallic tubing of claim 8, wherein the tubular-shaped body has been processed by melting nickel, titanium, and tungsten and cooling to the melt to form an alloy ingot, hot rolling the alloy ingot, cold and hot forming the alloy ingot into a cylinder, drilling the cylinder to form tubing, cold and hot drawing the tubing, and annealing the tubing.

18. The superelastic, radiopaque metallic tubing of claim 8, wherein the tubular-shaped body has an active austenite finish temperature A_f defined by −

15°

C.≦

active A_f≦

0°

C.

13. Radiopaque tubing for medical applications, comprising, wherein said alloy exhibits a stress-strain curve that approximates the idealized stress-strain curve of binary nickel-titanium;

a tubular body including a nickel-titanium alloy with at least a ternary element including tungsten, said alloy exhibiting a stress-strain curve that approximates the idealized stress-strain curve of binary nickel-titanium; and

wherein the tubular body includes approximately 5 to 12 atomic percent tungsten such that the tubular body is radiopaque and the tubular-shaped body includes a strut pattern with struts no greater than 0.0046 inch in width.

14. The radiopaque tubing of claim 13, wherein the tubular body includes 10 atomic percent tungsten.

15. The radiopaque tubing of claim 13, wherein strut pattern provides a ratio of open area to metal of approximately 80 percent.

16. The radiopaque tubing of claim 13, wherein the nickel-titanium alloy includes transformation temperatures measured by a Differential Scanning Calorimeter (DSC) test.

19. The radiopaque tubing of claim 13, wherein the tubular body has an austenite finish temperature ranging from −

15°

C. to 0°

C.