Target pedestal assembly and method of preserving the target

• US 7,835,502 B2
• Filed: 02/11/2009
• Issued: 11/16/2010
• Est. Priority Date: 02/11/2009
• Status: Active Grant

• Current Assignee: Accuray Incorporated
• Original Assignee: TomoTherapy Incorporated (Accuray Incorporated)
• Inventors: Spence, David Arthur, Schmidt, Richard Cary
• Primary Examiner(s): Kiknadze; Irakli
• Application Number:
  US12/369,449
• Publication Number:
  US 20100202593A1
• Time in Patent Office: 643 Days
• Field of Search: 378/119, 378/124, 378/125, 378/141, 378/143, 378/144, 378/199, 378/200, 378/204
• US Class Current: 378/143
• CPC Class Codes: A61B 6/4488 Means for cooling A61B6/045 takes precedence
• CPC Class Codes: H01J 2235/08 Targets (anodes) and X-ray converters
• CPC Class Codes: H01J 2235/085 Target treatment, e.g. ageing, heating
• CPC Class Codes: H01J 2235/086 Target geometry
• CPC Class Codes: H01J 2235/1204 of the anode
• CPC Class Codes: H01J 2235/1262 Circulating fluids
• CPC Class Codes: H01J 35/106 Active cooling, e.g. fluid flow, heat pipes

Abstract

An x-ray target pedestal assembly and a method of protecting the x-ray target from breaking down as a result of the extreme heat that is produced when an electron beam is aimed at the target to produce x-rays. The target is submerged in cooling fluid and is rotated by a constant flow of the cooling fluid over and around the target in order to dissipate heat. The fluid is guided by integrated flow diverters in the target cover. The target may also be protectively coated either in its entirety or along the electron beam path in order to further protect it from the heat of the electron beam impact or from breakdown as a result of attack of free radicals or other chemically reactive components of the cooling fluid which are produced in the extreme target environment.

Claims

1. A target pedestal assembly for a radiation delivery device, the target pedestal assembly comprising:

a pedestal subassembly coupled to a linear accelerator of the radiation delivery device, the pedestal subassembly including a first recessed area and an aperture positioned within the first recessed area;

a cover coupled to the pedestal subassembly, the cover including a second recessed area complementary to the first recessed area, the second recessed area including an aperture positioned within the second recessed area, the aperture not extending through the cover;

a target including an aperture therethrough; and

a pin configured to receive the target through the aperture, to be received within the aperture of the pedestal subassembly, to be received within the aperture of the cover, and to position the target between the first recessed area of the pedestal subassembly and the second recessed area of the cover, the pin further configured to prevent the target from being pinched by one of the first recessed area and the second recessed area.

2. The target pedestal assembly of claim 1 wherein the pin is configured to rotationally couple the target to the pedestal subassembly and the cover.

3. The target pedestal assembly of claim 1 wherein the pin includes a length configured to maintain a minimum gap between the target and the second recessed area of the cover and between the target and the first recessed area of the pedestal subassembly.

4. The target pedestal assembly of claim 1 wherein the pin comprises tungsten carbide.

5. The target pedestal assembly of claim 1 wherein the pedestal subassembly includes a first channel adjacent to the first recessed area, the first channel including a first flow diverter at a first end of the channel and a second flow diverter at a second end of the channel.

6. The target pedestal assembly of claim 5 wherein the cover includes a second channel complementary to the first channel, the second channel including a first flow diverter at a first end of the channel and a second flow diverter at a second end of the channel.

7. The target pedestal assembly of claim 6 wherein a portion of the target is positioned between the first channel and the second channel, at least a portion of the target being protected with a material sufficient to reduce chemical reactivity between the target and a cooling medium or its decomposition products flowing in the channel.

8. The target pedestal assembly of claim 7 wherein the cooling medium flowing within the first channel and the second channel propels rotation of the target.

9. The target pedestal assembly of claim 8 wherein flow of the cooling medium within the first channel and the second channel is substantially co-planar with the target.

10. The target pedestal assembly of claim 9 wherein the target rotates at a speed of about greater than about 2000 RPM.

11. The target pedestal assembly of claim 7 wherein the cooling medium is water.

12. The target pedestal assembly of claim 7 wherein the target protection is a coating material.

13. The target pedestal assembly of claim 12 wherein the coating material comprises chromium nitride.

14. The target pedestal assembly of claim 12 wherein the coating material is atomically bonded to the target through a physical vapor deposition process.

15. The target pedestal assembly of claim 12 wherein the coating material is applied to the entire target.

16. The target pedestal assembly of claim 12 wherein the radiation delivery device delivers a beam of radiation to the target along a beam path, and wherein the coating material is applied to a portion of the target outside of the beam path.

17. The target pedestal assembly of claim 7 wherein the target protection is a casing material comprising a material suitable for handling high amounts of radiation and low chemical reactivity to cooling medium or its decomposition product.

18. The target pedestal assembly of claim 17 wherein the casing material is bonded to the target.

19. The target pedestal assembly of claim 7 wherein the target protection is a protective surface applied to a portion of the target.

20. The target pedestal assembly of claim 19 wherein the protective surface is at a location where the target receives an electron beam.

21. A target pedestal assembly for a radiation delivery device, the target pedestal assembly comprising:

a housing coupled to a linear accelerator of the radiation delivery device, the housing defining a cavity and a channel adjacent to the cavity, the channel including a first flow diverter at a first end of the channel and a second flow diverter at a second end of the channel;

a target positioned within the cavity and rotationally coupled to the housing, a portion of the target positioned within the channel, the target including a serrated edge arranged around a perimeter of the target; and

a cooling medium positioned within the cavity and the channel, the target being protected with a material sufficient to reduce chemical reactivity between the target and the cooling medium.

22. The target pedestal assembly of claim 21 further comprising a pin configured to rotationally couple the target to the housing.

23. The target pedestal assembly of claim 22 wherein the pin includes a length configured to maintain a minimum gap between the target and the housing.

24. The target pedestal assembly of claim 22 wherein the pin comprises tungsten carbide.

25. The target pedestal assembly of claim 21 wherein the cooling medium flowing within the channel propels rotation of the target.

26. The target pedestal assembly of claim 25 wherein flow of the cooling medium within the channel is substantially co-planar with the target.

27. The target pedestal assembly of claim 26 wherein the target rotates at a speed greater than about 2,000 RPM.

28. The target pedestal assembly of claim 21 wherein the target protection is a coating material.

29. The target pedestal assembly of claim 28 wherein the coating material comprises chromium nitride.

30. The target pedestal assembly of claim 28 wherein the coating material is atomically bonded to the target through a physical vapor deposition process.

31. The target pedestal assembly of claim 21 wherein the target protection is a casing material comprising a material suitable for handling high amounts of radiation and low chemical reactivity to the cooling medium or its decomposition product.

32. The target pedestal assembly of claim 31 wherein the casing material is brazed to the target.

33. The target pedestal assembly of claim 21 wherein the target protection is a protective surface applied to a portion of the target.

34. The target pedestal assembly of claim 33 wherein the protective surface is at a location where the target receives an electron beam.

35. The target pedestal assembly of claim 34 wherein the cooling medium is water.

36. A target pedestal assembly for a radiation delivery device, the target pedestal assembly comprising:

a housing including a cavity and a cooling medium flowing within the cavity; and

a target comprising tungsten and positioned within the cavity, the target submerged in the cooling medium, the target being protected with a material sufficient to reduce chemical reactivity between the target and the cooling medium, and

wherein the cooling medium flowing within the cavity propels rotation of the target.

37. The target pedestal assembly of claim 36 further comprising a pin configured to rotationally couple the target to the housing.

38. The target pedestal assembly of claim 37 wherein the pin includes a length configured to maintain a minimum gap between the target and the housing.

39. The target pedestal assembly of claim 37 wherein the pin comprises tungsten carbide.

40. The target pedestal assembly of claim 36 wherein flow of the cooling medium within the cavity is substantially co-planar with the target.

41. The target pedestal assembly of claim 40 wherein the target rotates at a speed greater than about 2,000 RPM.

42. The target pedestal assembly of claim 36 wherein the target protection is a coating material.

43. The target pedestal assembly of claim 42 wherein the coating material comprises chromium nitride.

44. The target pedestal assembly of claim 42 wherein the coating material is atomically bonded to the target through a physical vapor deposition process.

45. The target pedestal assembly of claim 36 wherein the target protection is a casing material comprising a material suitable for handling high amounts of radiation and low chemical reactivity to the cooling medium or its decomposition product.

46. The target pedestal assembly of claim 45 wherein the casing material is brazed to the target.

47. The target pedestal assembly of claim 36 wherein the target protection is a protective surface applied to a portion of the target.

48. The target pedestal assembly of claim 47 wherein the protective surface is at a location where the target receives an electron beam.

49. The target pedestal assembly of claim 48 wherein the cooling medium is water.

50. A target pedestal assembly for a radiation delivery device, the target pedestal assembly comprising:

a housing including a cavity and a cooling medium flowing within the cavity; and

a target comprising tungsten and positioned within the cavity, the target submerged in the cooling medium, the target being protected with a material sufficient to reduce chemical reactivity between the target and the cooling medium; and

a pin configured to rotationally couple the target to the housing.

51. The target pedestal assembly of claim 50 wherein the pin includes a length configured to maintain a minimum gap between the target and the housing.

52. The target pedestal assembly of claim 50 wherein the pin comprises tungsten carbide.