Process for forming an improved metal alloy stent

• US 20060198750A1
• Filed: 01/30/2006
• Published: 09/07/2006
• Est. Priority Date: 03/03/2005
• Status: Active Grant

• Current Assignee: Mirus LLC
• Original Assignee: Icon Medical Corp. (ICON Interventional Systems, Inc.)
• Inventors: Furst, Joseph G., Patel, Udayan, Buckman, Raymond W. Jr.
• Granted Patent: US 7,540,994 B2
• Time in Patent Office: Days
• US Class Current: 419/5
• 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: A61P 35/00 Antineoplastic agents
• CPC Class Codes: A61P 37/06 Immunosuppressants, e.g. drugs for graft rejection
• CPC Class Codes: A61P 43/00 Drugs for specific purposes, not provided for in groups A61P1/00-A61P41/00
• CPC Class Codes: A61P 7/02 Antithrombotic agents; Anticoagulants; Platelet aggregation inhibitors
• CPC Class Codes: A61P 9/00 Drugs for disorders of the cardiovascular system
• CPC Class Codes: B22F 1/09 Mixtures of metallic powders
• CPC Class Codes: B22F 2003/248 Thermal after-treatment
• CPC Class Codes: B22F 2201/01 Reducing atmosphere
• CPC Class Codes: B22F 2201/10 Inert gases
• CPC Class Codes: B22F 2201/20 Use of vacuum
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 3/04 by applying fluid pressure , e.g. by cold isostatic pressing [CIP]
• CPC Class Codes: B22F 3/10 Sintering only
• CPC Class Codes: B22F 3/16 in successive or repeated steps
• CPC Class Codes: B22F 3/20 by extruding
• CPC Class Codes: B22F 3/24 After-treatment of workpieces or articles B22F3/1146 takes precedence
• CPC Class Codes: B22F 5/10 of articles with cavities or holes, not otherwise provided for in the preceding subgroups
• CPC Class Codes: B22F 5/106 : Tube or ring forms
• CPC Class Codes: C22C 27/00 : Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
• CPC Class Codes: C22C 27/04 : Alloys based on tungsten or molybdenum
• CPC Class Codes: C22C 30/00 : Alloys containing less than 50% by weight of each constituent
• CPC Class Codes: C22F 1/18 : High-melting or refractory metals or alloys based thereon
• CPC Class Codes: Y10S 606/907 : Composed of particular material or coated

Abstract

A method and process for at least partially forming a medical device that is at least partially formed of a novel metal alloy which improves the physical properties of the medical device.

Claims

1. A method for forming a medical device comprising the steps of:

a) forming a rod or tube having a surface and an outer diameter, said rod or tube including a metal alloy that is formed of at least about 99.9 weight percent of a solid solution and includes carbon and oxygen, said metal alloy having a carbon to oxygen atomic ratio of at least about 2;

1;

b) drawing down said outer diameter of said rod or tube by a reducing mechanism that reduces said outer diameter by less than about 25% each time said rod or tube is processed by said reducing mechanism;

c) cleaning said surface of said rod or tube; and

,

d) annealing said rod or tube prior to said rod or tube having said outer diameter draw down by more than about 50%.

2. The method as defined in claim 1, wherein said step of forming said rod or tube includes a process of isostatically pressing metal powder together and subsequently sintering said metal power to form said rod or tube.

3. The method as defined in claim 2, wherein said step of isostatically pressing metal powder together creates a rod or tube having an average density of about 0.7-0.95 a minimum theoretical density of said metal alloy.

4. The method as defined in claim 2, wherein said step of sintering said isostatically pressed metal powder creates a rod or tube average density of about 0.9-0.99 a minimum theoretical density of said metal alloy.

5. The method as defined in claim 2, wherein said step of sintering said isostatically pressed metal powder creates a rod or tube have an average density of about 12-14 gm/cc.

6. The method as defined in claim 2, wherein said step of sintering said isostatically pressed metal powder occurs in an inert atmosphere, an oxygen reducing atmosphere, or a vacuum.

7. The method as defined in claim 1, wherein said metal alloy includes about 46-49 weight percent rhenium, about 51-54 weight percent molybdenum, and up to about 0.5 weight percent additional metal, said additional metal including a metal selected from the group consisting of titanium, yttrium, zirconium, or mixtures thereof.

8. The method as defined in claim 1, wherein said step of drawing down said outer diameter of said rod or tube by a reducing mechanism that reduces said outer diameter by less than about 10% each time said rod or tube is processed by said reducing mechanism.

9. The method as defined in claim 1, wherein said reducing mechanism includes a plug drawing process.

10. The method as defined in claim 1, wherein said step of drawing down said outer diameter of said rod or tube at least partially occurs in an inert atmosphere, an oxygen reducing atmosphere, or a vacuum.

11. The method as defined in claim 1, wherein said step of annealing said rod or tube occurs prior to said rod or tube having said outer diameter drawn down by more than about 45%.

12. The method as defined in claim 1, wherein said step of annealing said rod or tube occurs at a temperature of at least about 1300°

C. for at least about 2 minutes.

13. The method as defined in claim 1, wherein said step of annealing said rod or tube occurs at least partially occurs in an inert atmosphere, an oxygen reducing atmosphere, or a vacuum.

14. The method as defined in claim 1, wherein said step of cleaning said surface occurs prior to each said step of annealing.

15. The method as defined in claim 1, wherein said step of cleaning said surface occurs after said step of drawing down said outer diameter of said rod or tube.

16. The method as defined in claim 1, including the step of cutting said annealed rod or tube at least partially into said medical device.

17. The method as defined in claim 16, wherein said step of cutting is at least partially by a laser.

18. The method as defined in claim 16, wherein step of cutting includes the step of restraining said rod or tube to inhibit vibration of said rod or tube as said rod or tube is at least partially cut.

19. The method as defined in claim 16, wherein said step of cutting at least partially occurs in an inert atmosphere, an oxygen reducing atmosphere, or a vacuum.

20. The method as defined in claim 16, including the step of electro-polishing said medical device after said step of cutting.

21. The method as defined in claim 1, wherein said medical device is a stent, graft, valve, screw, nail, rod, PFO device, prosthetic device, sheath, guide wire, balloon catheter, hypotube, catheter, electrophysiology catheter, staple or cutting device.

22. The method as defined in claim 1, including the step of applying at least one biological agent on at least one region of said medical device.

23. The method as defined in claim 22, including the step of applying at least one polymer to at least one region of said medical device to at least partially coat, encapsulate or combinations thereof said at least one biological agent.

24. The method as defined in claim 1, wherein the medical device is a stent and has a wall thickness of less than about 0.0027 inch.

25. A method for forming a medical device comprising the steps of:

a) selecting at least two different metal powders, said metal powders having an average particle size of less than about 200 mesh;

b) substantially homogeneously mixing together said metal powders;

c) forming a tube from said metal powders by pressing said metal powders together and sintering said metal powders, said tube having a surface and an outer diameter, said tube including a metal alloy that is formed of at least about 99.9 weight percent of a solid solution and includes carbon and oxygen, said metal alloy having a carbon to oxygen atomic ratio of at least about 2.5;

1;

d) drawing down said outer diameter of said tube by a plug drawing process to reduce said outer diameter of said tube by less than about 15% each time said tube is processed by said plug drawing process;

e) cleaning said surface of said tube after said plug drawing process;

f) annealing said tube prior to said tube having said outer diameter draw down by more than about 45% since said tube had been last sintered or annealed; and

,

g) laser cutting said annealed tube to at least partially form said medical device, said tube at least partially stabilized during said laser cutter such than an average amplitude of vibration of said tube during said laser cutter is no more than about 50% of a wall thickness of said tube.

26. The method as defined in claim 25, wherein said step of pressing said metal powders includes a process of isostatically pressing metal powders to create a tube having an average density of about 0.7-0.95 a minimum theoretical density of said metal alloy.

27. The method as defined in claim 25, wherein said step of sintering creates a tube having an average density of about 13-14 gm/cc.

28. The method as defined in claim 25, wherein said step of sintering occurs in an inert atmosphere, an oxygen reducing atmosphere, or a vacuum.

29. The method as defined in claim 25, wherein said substantially homogeneous mixture of metal powders includes about 46-49 weight percent rhenium, about 51-54 weight percent molybdenum, and up to about 0.5 weight percent additional metal, said additional metal including a metal selected from the group consisting of titanium, yttrium, zirconium, or mixtures thereof.

30. The method as defined in claim 25, wherein said step of drawing down said outer diameter of said tube reduces said outer diameter by less than about 10% each time said tube is processes by said plug drawing process, said step of drawing down said outer diameter of said tube at least partially occurring in an inert atmosphere, an oxygen reducing atmosphere, or a vacuum.

31. The method as defined in claim 25, wherein said step of annealing said tube occurs at a temperature of at least about 1300°

C. for at least about 2 minutes, and in an inert atmosphere, an oxygen reducing atmosphere, or a vacuum.

32. The method as defined in claim 25, wherein said tube is drawn down a plurality of times prior to at least one anneal step.

33. The method as defined in claim 25, wherein said step of cleaning said surface occurs prior to each said step of annealing.

34. The method as defined in claim 25, wherein said step of cutting said annealed tube occurs in an inert atmosphere, an oxygen reducing atmosphere, or a vacuum.

35. The method as defined in claim 25, including the step of electro-polishing said medical device after said step of laser cutting.

36. The method as defined in claim 25, wherein said medical device is a stent.

37. The method as defined in claim 28, including the step of applying at least one biological agent on at least one region of said medical device.

38. The method as defined in claim 37, including the step of applying at least one polymer to at least one region of said medical device to at least partially coat, encapsulate or combinations thereof said at least one biological agent.