Stationary computed tomography system with compact x ray source assembly

• US 7,068,749 B2
• Filed: 05/19/2003
• Issued: 06/27/2006
• Est. Priority Date: 05/19/2003
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Kollegal, Manohar Gopalaswamy, Bewlay, Bernard Patrick, Wilson, Colin Richard, Benz, Mark Gilbert
• Primary Examiner(s): Glick, Edward J.
• Assistant Examiner(s): Suchecki, Krystyna
• Application Number:
  US10/440,695
• Publication Number:
  US 20040234023A1
• Time in Patent Office: 1,135 Days
• Field of Search: 378/9, 378/10, 378/138, 378/141, 378/123
• US Class Current: 378/10
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/035 Mechanical aspects of CT
• CPC Class Codes: A61B 6/4028 resulting in acquisition of views from substantially different positions, e.g. EBCT
• CPC Class Codes: A61B 6/4275 using a detector unit almost surrounding the patient, e.g. more than 180°
• CPC Class Codes: A61B 6/4488 Means for cooling A61B6/045 takes precedence
• CPC Class Codes: H01J 35/13 Active cooling, e.g. fluid flow, heat pipes
• CPC Class Codes: H01J 35/147 Spot size control

Abstract

A stationary CT system comprising at least one annular x ray source assembly comprising a plurality of respective x ray sources spaced along the annular x ray source assembly. Each of the x ray sources comprises a respective stationary x ray target, an electron beam focusing chamber; an x ray channel; an electron beam source disposed in a spaced apart relationship with respect to the respective stationary x ray target; a vacuum chamber disposed in between the electron beam focusing chamber and an insulating chamber where the insulating chamber houses the electron beam source; a radiation window at a pre-defined angular displacement from the respective stationary x ray target and the x ray channel; and a target substrate attached to the respective stationary x ray target.

Claims

1. A stationary CT system comprising:

at least one annular x ray source assembly comprising a plurality of respective x ray sources spaced along said annular x ray source assembly,

wherein each of said respective x ray sources comprises a respective stationary x ray target;

an electron beam focusing chamber;

an x ray channel; and

an electron beam source disposed in a spaced apart relationship with respect to said respective stationary x ray target, and wherein said electron beam focusing chamber comprises a top section and a bottom section disposed in a spaced relationship to one another so as to have a selected cross-sectional profile so as to focus a plurality of electrons emitted from said electron beam source to impinge on said respective stationary x ray target to produce x rays that pass into said x ray channel, the top section further being configured to receive back-scattered electrons generated by the electron beam impact at the respective stationary x ray target and predominantly redirect the back-scattered electrons away from said electron beam source,

wherein said top section of said electron beam focusing chamber comprises a plurality of grooves located opposite said respective stationary x ray target to trap a plurality of back-scattered electrons and prevent said plurality of back-scattered electrons from hitting said respective stationary x ray target.

2. The system of claim 1, further comprising a plurality of detectors located along the annular length and spaced at an offset away from the annular x-ray source assembly to ensure optimal x-ray photon flux detection.

3. The system of claim 1, wherein each of said x ray sources further comprises a vacuum chamber disposed in between said electron beam focusing chamber and an insulating chamber, wherein said insulating chamber houses said electron beam source.

4. The system of claim 3, wherein said insulator chamber comprises an insulator medium.

5. The system of claim 4, wherein said insulator medium comprises at least one of a high temperature ceramic and a plastic.

6. The system of claim 3, wherein said electron beam source is adapted to be maintained at a negative potential with respect to said vacuum chamber and said electron beam focusing chamber.

7. The system of claim 1, wherein each of said x ray sources further comprises a radiation window at a pro-defined angular displacement from said respective stationary x ray target and said x ray channel.

8. The system of claim 7, wherein said radiation window is used as an exit path for a plurality of x rays produced by said respective stationary x ray target.

9. The system of claim 7, wherein radiation window comprises a material, wherein said material comprises at least one of aluminum and beryllium.

10. The system of claim 7, wherein said radiation window and said electron beam focusing chamber are coupled by a brazed contact.

11. The system of claim 7, wherein said radiation window and said electron beam focusing chamber are coupled by a mechanical contact.

12. The system of claim 7, wherein said radiation window is electrically isolated from said respective stationary x ray target.

13. The system of claim 12, wherein said radiation window is at a negative bias with respect to said respective stationary x ray target.

14. The system of claim 1, wherein said respective stationary x ray target comprises at least one of a metal and a metal alloy having an atomic number of at least about 40.

15. The system of claim 14, wherein said metal and said metal alloy comprise at least one selected from a group of Tungsten, Molybdenum, Rhenium, Rhodium and Zirconium.

16. The system of claim 1, wherein each of said x ray sources further comprises a target substrate attached to said respective stationary x ray target.

17. The system of claim 16, wherein said target substrate forms a bottom section of said electron beam focusing chamber and wherein said target substrate comprises a high thermal conductivity material selected from a group of copper, aluminum, graphite, graphite foams and metal foams of aluminum and copper.

18. The system of claim 16, wherein said target substrate comprises high thermal conductivity material having thermal conductivity greater than about 75 W/m/K.

19. The system of claim 16, wherein said respective stationary x ray target and said target substrate are at zero potential, and wherein said electron beam source is at negative potential.

20. The system of claim 16, wherein said respective stationary x ray target and said target substrate are at positive bias and said electron beam source is at negative bias.

21. The system of claim 18. wherein said respective stationary x ray target and said target substrate are at positive bias and said electron beam source is grounded.

22. The system of claim 16, wherein said target substrate comprises a plurality of cooling channels.

23. The system of claim 22, wherein said cooling channels are disposed such that a coolant can pass therethrough so to dissipate heat generated at said respective stationary x ray target.

24. The system of claim 22, wherein said cooling channels comprise heat storage materials to dissipate heat generated at said respective stationary x ray target.

25. The system of claim 24, wherein said heat storage materials comprise phase change materials, and wherein said phase change material comprise paraffin.

26. The system of claim 24, wherein said heat storage materials comprise at least one of sodium, potassium, tin, lead, indium, antimony, bismuth, sodium-potassium alloy, tin-lead alloy and indium-antimony alloy.

27. The system of claim 1, wherein said top section end said bottom section comprise a high thermal conductivity material selected from a group of copper, aluminum, graphite, graphite foams and metal foams of aluminum and copper, said top section and said bottom section defining a portion of an interior wall of said electro beam focusing chamber, the shape of said wall defining a portion of said selected cross sectional profile.

28. The system of claim 27, wherein said top section of said electron beam focusing chamber comprises a notch located opposite said respective stationary x ray target to trap a plurality of back-scattered electrons and to prevent said plurality of back-scattered electrons from hitting said respective stationary x ray target.

29. The system of claim 27, wherein said top section of said electron beam focusing chamber comprises a plurality of cooling channels.

30. The system of claim 29, wherein said cooling channels are configured to allow a coolant to be passed through said cooling channels and wherein said coolant comprises a liquid.

31. The system of claim 29, wherein said cooling channels comprise heat storage materials.

32. The system of claim 31, wherein said heat storage materials comprise phase change materials, wherein said phase change material comprise paraffin.

33. The system of claim 31, wherein said heat storage materials comprise at least one of sodium, potassium, tin, lead, indium, bismuth, sodium-potassium alloy, tin-lead alloy and indium-antimony alloy.

34. The system of claim 1, wherein the structure surrounding said electron beam focusing chamber comprises of high thermal conductivity material and wherein said high thermal conductivity material comprises at least one of copper, aluminum, graphite foams and metal foams of aluminum and copper.

35. The system of claim 1, wherein said electron beam source comprises a filament, wherein said filament is at least one of coiled filament and flat filament.

36. The system of claim 1, wherein said electron beam source comprises a field emitter array.

37. A stationary CT system comprising:

a plurality of x ray source assemblies, wherein each of said plurality of x ray source assemblies comprises a plurality of respective x ray sources spaced along each of respective annular x ray source assemblies,

wherein each of said plurality of respective x ray sources comprises, a respective stationary x ray target;

an electron beam focusing chamber;

an x ray channel; and

an electron beam source disposed in a spaced apart relationship with respect to said respective stationary x ray target, and wherein said electron beam focusing chamber comprises a top section and a bottom section disposed in a spaced relationship to one another so as to have a selected cross-sectional profile so as to focus a plurality of electrons emitted from said electron beam source to impinge on said respective stationary x ray target to produce x rays that pass into said x ray channel, the top section further being configured to receive back-scattered electrons generated by the electron beam impact at the respective stationary x ray target and predominantly redirect the back-scattered electrons away from said electron beam source,

wherein said too section comprises a plurality of grooves to trap a plurality of back-scattered electrons and prevent said plurality of back-scattered electrons from hitting said respective stationary x ray target.

38. The system of claim 37, wherein each of said plurality of respective x ray sources further comprises a vacuum chamber disposed in between said electron beam focusing chamber and an insulating chamber, wherein said insulating chamber houses said electron beam source.

39. The system of claim 37, wherein each of said plurality of respective x ray sources further comprises a radiation window at a pre-defined angular displacement from said respective stationary x ray target and said x ray channel, and wherein said radiation window is used as an exit path for a plurality of x rays produced by said respective stationary x ray target.

40. The system of claim 39, wherein said radiation window and said electron beam focusing chamber are coupled by a brazed contact.

41. The system of claim 39, wherein said radiation window and said electron beam focusing chamber are coupled by a mechanical contact.

42. The system of claim 37, wherein each of said plurality of respective x ray sources further comprises a target substrate attached to said respective stationary x ray target.

43. The system of claim 42, wherein said target substrate forms a bottom section of said electron beam focusing chamber.

44. The system of claim 42, wherein said target substrate comprises a plurality of cooling channels.

45. The system of claim 44, wherein a coolant is passed through said cooling channels to dissipate heat generated at said respective stationary x ray target and wherein said coolant comprises a liquid.

46. The system of claim 44, wherein said cooling channels comprise heat storage materials to dissipate heat generated at said respective stationary x ray target.

47. The system of claim 37, wherein said top section and said bottom section defining a portion of an interior wall of said electron beam focusing chamber, the shape of said wall defining a portion of said selected cross sectional profile.

48. The system of claim 47, wherein said top section said comprises a notch to trap a plurality of back-scattered electrons and to prevent said plurality of back-scattered electrons from hitting said respective stationary x ray target.

49. The system of claim 47, wherein said top section comprises a plurality of cooling channels.

50. The system of claim 49, wherein said cooling channels are configured to allow a coolant to be passed through said cooling channels and wherein said coolant comprises a liquid.

51. The system of claim 49, wherein said cooling channels comprise heat storage materials.

52. The system of claim 51, wherein said heat storage materials comprise phase change materials.

53. A stationary CT system comprising;

at least one annular x ray source assembly comprising a plurality of respective x ray sources spaced along said annular x ray source assembly, wherein each of said x ray sources comprises,

at respective stationary x ray target;

an electron beam focusing chamber;

an x ray channel;

an electron beam source disposed in a spaced apart relationship with respect to said respective stationary x ray target, and wherein said electron beam focusing chamber has a selected cross-sectional profile so as to focus a plurality of electrons emitted from said electron beam source to impinge on said respective stationary x ray target to produce x rays that pass into said x ray channel;

a vacuum chamber disposed in between said electron beam focusing chamber and an insulating chamber, wherein said insulating chamber houses said electron beam source;

a radiation window at a pre-defined angular displacement from said respective stationary x ray target and said x ray channel; and

a target substrate attached to said respective stationary x ray target, wherein said target substrate forms a bottom section of said electron beam focusing chamber,

wherein said selected cross-sectional profile of said electron beam focusing chamber comprises a top section and a bottom section disposed in a spaced relationship to one another, wherein said top section and said bottom section comprise a high thermal conductivity material selected from a group of copper, aluminum, graphite, graphite foams and metal foams of aluminum and copper, wherein the top section further being configured to receive back-scattered electrons generated by the electron beam impact at the respective stationary x ray target and predominantly redirect the back-scattered electrons away from said electron beam source,

wherein said top section comprises a plurality of grooves to trap a plurality of back-scattered electrons and prevent said plurality of back-scattered electrons from hitting said respective stationary x ray target.

54. The system of claim 53, wherein said target substrate comprises a plurality of cooling channels.

55. The system of claim 54, wherein said cooling channels are configured to allow a coolant to be passed through said cooling channels to dissipate heat generated at said respective stationary x ray target and wherein said coolant comprises a liquid.

56. The system of claim 54, wherein said cooling channels comprise heat storage materials to dissipate heat generated at said respective stationary x ray target.

57. The system of claim 53, wherein said top section comprises a notch to trap a plurality of back-scattered electrons and to prevent said plurality of back-scattered electrons from hitting said respective stationary x ray target.

58. The system of claim 53, wherein said top section comprises a plurality of cooling channels.

59. The system of claim 58, wherein said cooling channels are configured to allow a coolant to be passed through said cooling channels and wherein said coolant comprises a liquid.

60. The system of claim 58, wherein said cooling channels comprise heat storage materials.

61. The system of claim 60, wherein said heat storage materials comprise phase change materials.