Thermoelastic and superelastic NI-TI-W alloy
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.
1. An endoprosthesis delivery system comprising:
a delivery sheath and an endoprosthesis disposed within the delivery sheath, the endoprosthesis comprising:
a tubular-shaped body, the body including a nickel-titanium superelastic alloy, and the alloy further includes a ternary element including tungsten, wherein the tubular-shaped body includes a nickel-titanium-tungsten tubing having an austenite finish temperature of −15 degrees C. to 0 degrees C.
2. The endoprosthesis delivery system of claim 1 , wherein the endoprosthesis delivery system is configured to be passed through a body lumen over a guidewire.
3. The endoprosthesis delivery system of claim 1 , wherein the atomic percent of the tungsten is greater than or equal to 5 and less than or equal to 12.
4. The endoprosthesis delivery system of claim 1 , wherein the atomic percent of the nickel is 50.8, the atomic percent of the tungsten is 10, and a balance is the atomic percent of titanium.
5. The endoprosthesis delivery system of claim 1 , wherein the superelastic alloy includes a stress-induced martensite phase.
6. The endoprosthesis delivery system of claim 1 , wherein the atomic percent of the nickel is 50.8 and the atomic percent of the titanium is a maximum of approximately 40.
7. The endoprosthesis delivery system of claim 1 , wherein an austenite finish temperature (A f ) of the superelastic alloy in the endoprosthesis is greater than or equal to zero and less than or equal to 30 degrees C.
8. The endoprosthesis delivery system 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.
9. The endoprosthesis delivery system of claim 1 , wherein the endoprosthesis has a greater radiopacity than a 316L stainless steel endoprosthesis coated with 4.7 μm of gold.
10. An endoprosthesis delivery system comprising:
a delivery sheath;
a delivery catheter configured to be disposed within the delivery sheath; and
an endoprosthesis disposed adjacent to a distal end of the delivery catheter, the endoprosthesis 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 pattern with struts no greater than 0.0046 inch in width.
11. The endoprosthesis delivery system of claim 10 , wherein the atomic percent of the tungsten is greater than or equal to 5 and less than or equal to 12.
12. The endoprosthesis delivery system of claim 10 , wherein the atomic percent of the nickel is 50.8, the atomic percent of the tungsten is 10, and a balance is the atomic percent of titanium.
13. The endoprosthesis delivery system of claim 10 , wherein the superelastic alloy includes a stress-induced martensite phase.
14. The endoprosthesis delivery system of claim 10 , wherein the atomic percent of the nickel is 50.8 and the atomic percent of the titanium is a maximum of approximately 40.
15. The endoprosthesis delivery system of claim 10 , wherein the superelastic alloy in the tubular-shaped body has an austenite finish temperature (A f ) of greater than or equal to zero and less than or equal to 30 degrees C.
16. The endoprosthesis delivery system of claim 10 , 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. An endoprosthesis delivery system comprising:
a delivery sheath;
a delivery catheter configured to be disposed within the delivery sheath; and
an endoprosthesis disposed on the deliver catheter, the endoprosthesis comprising:
a tubular-shaped body wherein the body includes a nickel-titanium superelastic alloy with a ternary element including tungsten, wherein the nickel-titanium superelastic alloy includes:
30 to 52 atomic percent titanium,
5 to 12 atomic percent tungsten, and
a balance of nickel;
wherein the tubular-shaped body is formed from a nickel-titanium-tungsten tubing having an austenite finish temperature (A f ) of −15 degree C. to 0 degree C., wherein the body is radiopaque.
18. The endoprosthesis delivery system of claim 17 , wherein the nickel-titanium superelastic alloy includes 50.8 atomic percent nickel, 10 atomic percent tungsten, and a balance of titanium.
19. The endoprosthesis delivery system of claim 17 , wherein the tubular-shaped body includes a strut pattern with struts no greater than 0.0046 inch in width.
20. The endoprosthesis delivery system of claim 17 , wherein the superelastic alloy includes a stress-induced martensite phase.
21. The endoprosthesis delivery system of claim 17 , wherein an austenite finish temperature (A f ) of the superelastic alloy in the tubular-shaped body of the endoprosthesis is greater than or equal to zero and less than or equal to 30 degrees C.
22. An endoprosthesis delivery system comprising:
a delivery sheath and an endoprosthesis disposed within the delivery sheath, the endoprosthesis comprising:
a tubular-shaped body including:
an atomic percent of nickel of 50.8,
an atomic percent of tungsten greater than or equal to 5 and less than or equal to 12, and
a balance of titanium
wherein the tubular-shaped body has an active austenite finish temperature A f defined by −15 degree C.≦active A f ≦0 degree C.
23. The endoprosthesis delivery system of claim 22 , wherein the tubular-shaped body includes 50.8 atomic percent nickel, 10 atomic percent tungsten, and a balance of titanium.
24. The endoprosthesis delivery system of claim 22 , wherein the tubular-shaped body includes a strut pattern having struts and each strut has a cross-sectional area of less than 0.000021 in 2 .