Computed tomography system for imaging of human and small animal

• US 20040213378A1
• Filed: 04/24/2003
• Published: 10/28/2004
• Est. Priority Date: 04/24/2003
• Status: Abandoned Application

• Current Assignee: University of North Carolina At Chapel Hill (University of North Carolina System)
• Original Assignee: University of North Carolina At Chapel Hill (University of North Carolina System)
• Inventors: Zhou, Otto Z., Cheng, Yuan, Zhang, Jian, Lu, Jianping, Lee, Yueh, Lin, Weili
• Application Number:
  US10/421,931
• Publication Number:
  US 20040213378A1
• Time in Patent Office: Days
• US Class Current: 378/122
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4028 resulting in acquisition of views from substantially different positions, e.g. EBCT
• CPC Class Codes: A61B 6/4085 Cone-beams
• CPC Class Codes: A61B 6/4275 using a detector unit almost surrounding the patient, e.g. more than 180°
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: A61B 6/508 for non-human patients
• CPC Class Codes: A61B 6/5235 combining images from the same or different ionising radiation imaging techniques, e.g. PET and CT
• CPC Class Codes: A61B 6/541 involving acquisition triggered by a physiological signal
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic

Abstract

Computed tomography device comprising an x-ray source and an x-ray detecting unit. The x-ray source comprises a cathode with a plurality of individually programmable electron emitting units that each emit an electron upon an application of an electric field, an anode target that emits an x-ray upon impact by the emitted electron, and a collimator. Each electron emitting unit includes an electron field emitting material. The electron field emitting material includes a nanostructured material or a plurality of nanotubes or a plurality of nanowires. Computed tomography methods are also provided.

Claims

1. A computed tomography device, comprising:

an x-ray source, the x-ray source comprising a cathode with a plurality of individually programmable electron emitting units that each emit an electron beam upon an application of an electric field, an anode target that emits an x-ray beam upon impact by the emitted electron beam, and a collimator; and

an x-ray detecting unit.

2. The device of claim 1, wherein each electron emitting unit includes an electron field emitting material.

3. The device of claim 2, wherein the electron field emitting material includes a nanostructured material.

4. The device of claim 2, wherein the electron field emitting material includes a plurality of nanotubes or a plurality of nanowires.

5. The device of claim 4, wherein the nanotubes includes at least one field emitting material selected from the group consisting of carbon, boron, nitrogen, sulfur, and tungsten.

6. The device of claim 4, wherein the nanowires included at least one field emitting material selected from the group consisting of silicon, germanium, carbon, oxygen, indium, cadmium, gallium, oxide, nitrides, silicides and boride.

7. The device of claim 2, wherein the electron field emitting material includes a plurality of single-wall carbon nanotubes, a plurality of multi-wall carbon nanotubes, a plurality of double-wall carbon nanotubes, or a mixture thereof.

8. The device of claim 1, wherein the x-ray source further comprises a gate electrode to extract the emitted electron from one or more of the plurality of individually programmable electron emitting units when the electrical field is applied between the gate electrode and the one or more individually programmable electron emitting units.

9. The device of claim 8, wherein the gate electrode is located between the cathode and the anode target, or located on the same plane as the cathode, the gate electrode electrically isolated from the cathode, or located behind the cathode to form a back-gate structure, the gate electrode.

10. The device of claim 8, wherein the electrical field is applied such that the gate electrode is at a positive potential with respect to the one or more of the plurality of individually programmable electron emitting units, and a field strength of the electrical field is from 0.1 Volt/micron to 100 Volt/micron.

11. The device of claim 10, wherein the field strength is from 0.5 Volt/micron to 20 Volt/micron.

12. The device of claim 8, wherein a frequency and a pulse width of the electrical field applied to the gate electrode are synchronized with the x-ray detecting unit for data collection such that an object is exposed to x-ray beam when the x-ray detecting unit is operative to collect data.

13. The device of claim 12, wherein the frequency and the pulse width are synchronized with a physiological signal of the object or an external signal source.

14. The device of claim 1, further comprising a monochromator placed in a path of the emitted x-ray after the collimator.

15. The device of claim 14, wherein the monochromator includes a crystal that selects an x-ray photon with a certain energy.

16. The device of claim 1, wherein the x-ray detecting unit includes a x-ray scintillation material and a digital imaging acquisition device.

17. The device of claim 16, wherein the digital imaging acquisition device includes a charge-coupled-device.

18. The device of claim 1, further comprising a control system for data collection and reconstruction.

19. The device of claim 1, further comprising a vacuum container housing the cathode and the anode target.

20. The device of claim 1, wherein at least one of the plurality of individually programmable electron emitting units has an emission threshold of less than 3 Volt/micron for a current density of greater than 0.01 mA/cm² and emits 0.1-100 mA total current.

21. The device of claim 20, wherein the current density is greater than 0.1 mA/cm².

22. The device of claim 1, wherein the emission current is less than or equal to 100 μ

A per nanotube at an electrical field of less than 100 V/μ

m.

23. The device of claim 1, wherein the plurality of individually programmable electron emitting units are arranged linearly on an axis in a plane and each individually programmable electron emitting unit is focused at one of a plurality of focal spots on the anode target.

24. The device of claim 23, wherein the collimator generates a fan beam, a cone beam, or a pencil beam geometry of x-ray radiation

25. The device of claim 23, wherein the plurality of focal spots are arranged linearly on the x-ray detecting unit.

26. The device of claim 23, further comprising an object stage between the anode target and the x-ray detecting unit.

27. The device of claim 26, wherein the object stage is non-stationary with respect to the x-ray source.

28. The device of claim 23, wherein the x-ray source is a transmission x-ray source.

29. The device of claim 22, wherein the x-ray source is a reflection x-ray source.

30. The device of claim 1, wherein the plurality of individually programmable electron emitting units are arranged linearly in an arch and each individually programmable electron emitting unit is focused at one of a plurality of focal spots on the anode target.

31. The device of claim 30, wherein the collimator generates a fan beam, a cone beam, or a pencil beam geometry of x-ray radiation.

32. The device of claim 30, wherein the arch is positioned such that each focal spot is equidistant from a center of rotation of an object stage and each focal spot focuses on a central rotation axis of the object stage.

33. The device of claim 30, wherein the plurality of focal spots are arranged linearly on the x-ray detecting unit.

34. The device of claim 30, further comprising an object stage between the anode target and the x-ray detecting unit.

35. The device of claim 34, wherein the object stage is non-stationary with respect to the x-ray source.

36. The device of claim 30, wherein the x-ray source is a transmission x-ray source.

37. The device of claim 30, wherein the x-ray source is a reflection x-ray source.

38. The device of claim 1, wherein the plurality of individually programmable electron emitting units are arranged over an area of a plane and each individually programmable electron emitting unit is focused at one of a plurality of focal spots on the anode target.

39. The device of claim 38, wherein the collimator generates a fan beam, a cone beam, or a pencil beam geometry of x-ray radiation.

40. The device of claim 38, further comprising an object stage between the anode target and the x-ray detecting unit.

41. The device of claim 40, wherein the object stage is non-stationary with respect to the x-ray source.

42. The device of claim 38, wherein the x-ray source is a transmission x-ray source.

43. The device of claim 38, wherein the x-ray source is a reflection x-ray source.

44. The device of claim 1, wherein the device is portable

45. The device of claim 1, wherein the device is a micro-computed tomography system.

46. A method to operate a computed tomography device, the computed tomography device including an x-ray source, the x-ray source comprising a cathode with a plurality of individually programmable electron emitting units that each emit an electron beam upon an application of an electric field, an anode target that emits an x-ray beam upon impact by the emitted electron beam, a collimator, and an x-ray detecting unit, the method comprising:

applying the electric field to at least a first of the plurality of individually programmable electron emitting units to cause the emission of an electron beam;

focusing the emitted electron beam at one of a plurality of focal points on the anode target;

impacting the anode target with the emitted electron beam to form an emitted x-ray radiation beam;

collimating the emitted x-ray radiation beam;

passing the collimated x-ray radiation beam through an object;

detecting the x-ray radiation beam with the x-ray detecting unit; and

recording the detected x-ray radiation beam as an x-ray radiation image.

47. The method of claim 46, further comprising repeating the steps of applying, focusing, impacting, collimating, passing, detecting, and recording to produce multiple x-ray radiation images without rotating the object positioned on the object stage.

48. The method of claim 47, wherein the electric field is applied to at least a second individually programmable electron emitting unit during the repeated step of applying.

49. The method of claim 47, wherein the emitted electron beam is focused on a second of the plurality of focal points on the anode target when the step of focusing is repeated.

50. The method of claim 47, wherein the step of collimating produces a fan-beam geometry of x-ray radiation and the recorded x-ray radiation is a magnified stereo-projection image of the object.

51. The method of claim 47, wherein the step of collimating produces a pencil beam geometry of x-ray radiation and the x-ray radiation image is a parallel projection image of the object.

52. The method of claim 46, wherein the object is on an object stage and the method further comprises:

rotating the object on the object stage through a set of angles; and

repeating, after each rotation of the object, the steps of applying, focusing, impacting, collimating, passing, detecting, and recording to obtain a series of x-ray radiation images.

53. The method of claim 52, comprising reconstructing a three-dimensional volume of the object positioned on the object stage from the series of x-ray radiation images.

54. The method of claim 53, wherein the x-ray radiation images are reconstructed using an image reconstructing algorithm to form the three-dimensional volume of the object.

55. The method of claim 46, wherein the x-ray source further includes a gate electrode located between the cathode and the anode target and the electrical field is applied such that the gate electrode is at a positive potential with respect to the individually programmable electron emitting unit and a field strength of the electrical field is from 0.1 Volt/micron to 100 volt/micron.

56. The method of claim 55, wherein the field strength is from 0.5 Volt/micron to 20 Volt/micron.

57. The method of claim 55, wherein the electrical field is established between the gate electrode and the individually programmable electron emitting unit simultaneously

58. The method of claim 46, wherein the emitted electron beam is accelerated to a given energy by the electrical field established between the cathode and the anode target.

59. The method of claim 46, wherein the electron beam emitted from each electron emitting unit is focused at a different one of the plurality of focal spots within a line on the anode target.

60. The method of claim 59, wherein the collimator generates a fan beam, a cone beam, or a pencil beam geometry of x-ray radiation.

61. The method of claim 60, wherein the fan beam geometry of x-ray radiation from each focal point passes through a slice of the object on the object stage and is detected by one or more pixels of the x-ray detecting unit to form a slice image.

62. The method of claim 61, wherein a plurality of slice images of the object are formed simultaneously and combined digitally to form a two-dimensional image of the object.

63. The method of claim 46, further comprising rotating the object from a first position to a second position by an angle between 0.1 and 10 degree in a discrete step and obtaining one two-dimensional image at the first position and the second position.

64. The method of claim 63, wherein the obtained two-dimension images are combined using an image reconstruction algorithm to form a three-dimension image of the object.

65. The method of claim 46, wherein an electrical field is established between the gate electrode and at least two of the plurality of individually programmable electron emitting units sequentially, one individually programmable electron emitting unit at a given time, from a first location on the cathode to a second location on the cathode, the sequential establishment of the electrical field having an on-off frequency between any two sequential individually programmable electron emitting units of from 0.01 to 10⁶ Hz

66. The method of claim 65, wherein a dwell time on each unit is from 1 μ

sec to 1 minute.

67. The method of claim 65, wherein a plurality of views of the object are collected.

68. The method of claim 46, wherein an electrical field is established between the gate electrode and at least two of the plurality of individually programmable electron emitting units sequentially, one individually programmable electron emitting unit at a given time, from a first location on the cathode to a second location on the cathode at a sweep rate of 0.01 to 10⁶ Hz.

69. The method of claim 68, wherein a plurality of views of the object are collected.

70. The method of claim 46, wherein the step of collimating produces a fan beam geometry, a cone beam geometry, or a pencil beam geometry.

71. The method of claim 46, wherein the step of collimating produces a fan beam geometry that illuminates an entire object.

72. The method of claim 46, wherein the step of collimating produces a pencil beam geometry that illuminates a portion of an object.