Computed tomography system for imaging of human and small animal

• US 20060008047A1
• Filed: 08/20/2004
• Published: 01/12/2006
• Est. Priority Date: 10/06/2000
• Status: Active Grant

• 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
• Granted Patent: US 7,082,182 B2
• Time in Patent Office: Days
• US Class Current: 378/10
• 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 6/508 for non-human patients
• 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
• CPC Class Codes: G01N 2223/316 collimators
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 2223/612 biological material
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]
• CPC Class Codes: H01J 2201/30469 Carbon nanotubes (CNTs)
• CPC Class Codes: H01J 2235/068 Multi-cathode assembly
• CPC Class Codes: H01J 35/065 Field emission, photo emission or secondary emission cathodes

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, and nitrogen.

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, oxide, and nitrides.

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 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.

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 the electrical field applied to the gate electrode is controlled by a feedback mechanism from the x-ray detecting unit.

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.

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 geometry of x-ray radiation.

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 geometry of x-ray radiation.

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

13-17. -17. (canceled)

22. (canceled)

25-37. -37. (canceled)

40-43. -43. (canceled)

45. (canceled)

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

processing the detected x-ray radiation image into a tomographic image.

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.

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 geometry of x-ray radiation.

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

47. (canceled)

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. (canceled)

51. (canceled)

52. 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,

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.

57. (canceled)

58. (canceled)

61. (canceled)

62. (canceled)

63. 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,

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. 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,

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. 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,

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.

71. (canceled)

72. (canceled)

73. A computed tomography device for small animal imaging, comprising:

a field emission x-ray source, wherein the x-ray source can generate a plurality of x-ray beams from a plurality of focal spots which are arranged in a two-dimensional matrix on a surface of an x-ray anode,

an area multi-pixel digital x-ray detector, and

an object stage placed between the x-ray source and the detector.

74. The device of claim 73, wherein the x-ray source comprises:

a cathode with a plurality of individually programmable electron emitting units that each emit an electron beam upon an application of an electric field, wherein the emitting units are positioned in a two-dimensional matrix on the cathode;

an electron focusing device; and

an anode target that emits an x-ray beam from a focal spot upon impact by an emitted electron beam.

75. 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, 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;

passing the x-ray radiation beam through an object;

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

rotating the detector and x-ray source pair 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.

76. The method of claim 75, wherein the obtained two-dimension images are combined using an image reconstruction algorithm to form a three-dimension image of the object.