Radiation scanning of objects for contraband

• US 20040017888A1
• Filed: 07/24/2002
• Published: 01/29/2004
• Est. Priority Date: 07/24/2002
• Status: Active Grant

• Current Assignee: Varex Imaging Corporation
• Original Assignee: Varian Medical Systems Incorporated (Siemens AG)
• Inventors: Seppi, Edward J., Ford, John, Marc, Marcel
• Granted Patent: US 7,103,137 B2
• Time in Patent Office: Days
• US Class Current: 378/57
• CPC Class Codes: G01N 2223/423 multispectral imaging-multiple energy imaging
• CPC Class Codes: G01N 23/04 and forming images of the material
• CPC Class Codes: G01T 1/2985 In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis); using external radiation sources A61B6/02
• CPC Class Codes: G01V 5/226 using tomography

Abstract

A scanning unit for identifying contraband, such as guns, explosives and illegal drugs, within objects, such as cargo containers and luggage, moving through the unit along a first path comprises at least one source of a beam of radiation movable across a second path that is transverse to the first path and extends partially around the first path. A stationary detector transverse to the first path also extends partially around the first path, positioned to detect radiation transmitted through the object during scanning. In one example, a plurality of movable X-ray sources, each transmitting a cone beam of radiation, are supported by a semi-circular rail perpendicular to the first path. In this example, the detector, which may be a detector array comprising a plurality of two-dimensional detectors, is also semi-circular and perpendicular to the path. A fan beam may also be used. Radiographic images may be obtained and/or computed tomography (“CT”) images may be reconstructed. The images may be analyzed for contraband. Energy sensitive detectors may also be provided. The radiation sources may emit radiation of different energy distributions or each source may selectively emit radiation of different energy distributions. Data derived from a voxel of the object at the different energy distributions may be processed to determine the material content of the voxel. Images based on that data can be fused with the radiographic or CT images to facilitate identification of contraband based on size, shape and material content of regions within the object. Methods of scanning objects are also disclosed.

Claims

1. A scanning unit for examining contents of an object, the scanning unit comprising:

a first path through the scanning unit to transport an object;

at least one source of a beam of radiation, the at least one source being movable across a second path transverse to the first path, the second path being within a first region extending partially around the first path; and

a stationary detector in a second region extending partially around the first path, the detector array being positioned to detect radiation transmitted through the object during scanning.

2. The scanning unit of claim 1, wherein the object is a cargo container and the detector and the at least one source of radiation is positioned to allow the cargo container to be transported therebetween, along the first path.

3. The scanning unit of claim 2, wherein the cargo container is carried by a vehicle;

and

the detector and the at least one source of radiation is positioned to allow the cargo and the vehicle to be transported therebetween.

4. The scanning unit of claim 1, wherein the detector is located, at least in part, beneath the first path, below ground;

and

the at least one source is located above the first path.

5. The scanning unit of claim 1, wherein the at least one source is movable about a semi-circle, the semi-circle lying on an imaginary circle having a center within the cargo container when the cargo container is in a position for scanning.

6. The scanning unit of claim 5, comprising a plurality of sources of radiation, the scanning unit further comprising;

a semi-circular rail perpendicular to the first path; and

wherein the plurality of sources are supported by the rail and are movable with respect to the rail, about the semi-circle.

7. The scanning unit of claim 5, wherein the detector is a detector array comprising a semi-circular row of detectors perpendicular to the first path and lying on an imaginary circle having a center within the object when the object is in a position for scanning.

8. The scanning unit of claim 1, wherein the detector comprises a plurality of two dimensional detectors.

9. The scanning unit of claim 1, comprising at least one energy sensitive detector.

10. The scanning unit of claim 1, wherein the at least one source is a source of X-ray radiation.

11. The scanning unit of claim 1, wherein the beam is a cone beam.

12. The scanning unit of claim 1, further comprising a processor electrically coupled to the detector array, the processor being programmed to reconstruct computed tomography images based on data received from the detector array.

13. The scanning unit of claim 1, further comprising a transport system to convey the object through the scanning unit, along the first path.

14. The scanning unit of claim 1, wherein the first region and the second region are wholly separate regions.

15. The scanning unit of claim 1, wherein each of the at least one sources is a linear accelerator.

16. A scanning unit for examining the contents of an object, the scanning unit comprising:

a first path through the scanning unit to transport an object;

a plurality of sources of X-ray radiation on a first side of the path, each source to provide a cone beam of X-ray radiation and being mechanically movable across a second path transverse to the first path, the second path being within a first region extending partially around the first path; and

a detector in a second region extending partially around the first path, the detector being positioned to detect each of the radiation beams emitted by the plurality of sources after each beam passes through the object during scanning.

17. The scanning unit of claim 16, wherein the object is a cargo container and the X-ray sources and the detector are positioned to allow transport of the cargo container therebetween.

18. The scanning unit of claim 16, further comprising:

a semi-circular rail supported by the scanning unit perpendicular to the first path,

the semi-circular rail lying on an imaginary circle having a center within the object when the object is in position for scanning,

wherein the rail supports the plurality of sources, the sources being movable in a semi-circle about the rail; and

the detector array is semi-circular,

is perpendicular to the path, and

lies on an imaginary circle having a center within the cargo when the cargo is in position for scanning.

19. The scanning unit of claim 16, wherein the detector is a detector array comprising a plurality of rows of detector modules.

20. The scanning unit of claim 16, wherein at least one of the sources emits radiation having a first energy distribution and at least one of the sources emits radiation having a second energy distribution different than the first energy distribution.

21. The scanning unit of claim 20, further comprising a second, energy sensitive, detector,

wherein the first detector is between the second detector and the plurality of sources.

22. The scanning unit of claim 21, further comprising a processor electrically coupled to the first and second detector, the processor being programmed to:

reconstruct computed tomography images based on data received from the first detector;

reconstruct energy based images based on data received from the second detector; and

fuse the images based on data from the first detector array with the images based on the data received from the second detector.

23. The scanning unit of claim 16, wherein each of the plurality of sources are operational to selectively switch between emitting radiation having a first energy distribution and radiation having a second energy distribution different than the first energy distribution.

24. The scanning unit of claim 23, further comprising a second, energy sensitive, detector,

wherein the first detector is between the second detector and the plurality of sources.

25. The scanning unit of claim 24, further comprising a processor electrically coupled to the first detector, the processor being programmed to:

reconstruct computed tomography images based on data received from the first detector;

reconstruct energy based images based on data received from the second detector; and

fuse the images based on data from the first detector array with the images based on the data received from the second detector array.

26. The screening unit of claim 16, further comprising a processor electrically connected to the detector, the processor being programmed to reconstruct computed tomography images based on data received from the detector.

27. The scanning unit of claim 16, wherein the cone beam is an asymmetric rectangular cone beam.

28. A cargo scanning unit comprising:

a path through the scanning unit for transport of a cargo container;

a semi-circular rail supported by the unit above the path, transverse to the path, the semi-circular rail lying on a first imaginary circle having a center within the cargo when the cargo is in position for scanning;

a plurality of movable sources of X-ray radiation supported by the rail, each source to provide a cone beam of X-ray radiation; and

a semi-circular detector array having at least a portion below the path, beneath ground level, the detector array being transverse to the path and lying on a second imaginary circle having a center within the cargo when the cargo is in position for scanning;

wherein the first and second imaginary circles lie in a same plane; and

the detector array comprises a plurality of two dimensional detectors.

29. The cargo scanning unit of claim 28, wherein the detector array is stationary.

30. The cargo scanning unit of claim 28, wherein at least one of the sources emits radiation having a first energy distribution and at least one of the sources emits radiation having a second energy distribution different than the first energy distribution.

31. The cargo scanning unit of claim 28, further comprising a second, energy sensitive, detector array,

wherein the first detector array is between the second detector array and the plurality of sources.

32. The cargo scanning unit of claim 28, wherein each of the plurality of sources are operational to selectively switch between emitting radiation having a first energy distribution and radiation having a second energy distribution different than the first energy distribution.

33. The cargo scanning unit of claim 28, further comprising a second, energy sensitive, detector array,

wherein the first detector array is between the second detector array and the plurality of sources.

34. The cargo scanning unit of claim 28, wherein the X-ray sources are linear accelerators having acceleration energies greater than about 1 MeV.

35. The cargo scanning unit of claim 28, wherein the cone beam covers an angle of about 20 to about 30 degrees.

36. A method of examining contents of a cargo container, comprising:

scanning at least a portion of the cargo container with a radiation beam at a plurality of angles;

detecting radiation transmitted through the cargo container; and

processing data based on the detected radiation to form computed tomographic images of at least the portion of the cargo container.

37. The method of claim 36, further comprising:

moving the cargo container along a path in a first direction;

scanning at least a portion of the cargo container by a plurality of radiation beams, each scanning the cargo container at a different angle; and

detecting radiation transmitted through the cargo container by a stationary detector.

38. The method of claim 37, further comprising:

moving a source of the radiation beam in a second direction transverse to the first direction to scan the cargo container; and

detecting radiation transmitted through the cargo container by a stationary detector;

39. The method of claim 36, comprising scanning the cargo container with a cone beam of radiation.

40. The method of claim 36, comprising scanning the cargo container with X-ray radiation.

41. The method of claim 36, comprising scanning the cargo container with a radiation beam having a first energy distribution and scanning the cargo container with a radiation beam having a second energy distribution different from the first energy distribution.

42. The method of claim 41, comprising:

detecting radiation with a first, spatial detector;

detecting radiation with a second, energy sensitive, detector; and

processing data based on the detected radiation from the first and second detectors to form respective computed tomographic images of the cargo container.

43. The method of claim 42, comprising:

fusing corresponding computed tomographic images from the radiation detected from the first and second detectors.

44. The method of claim 36, further comprising:

first;

scanning the entire cargo container with a beam of radiation,

producing radiographs of the cargo container, and

identifying suspicious regions of the cargo container based on the radiographs,

and then;

scanning the suspicious regions of the cargo container with a radiation beam at the plurality of angles,

detecting radiation transmitted through the cargo container, and

processing data based on the detected radiation to form computed tomographic images of the suspicious regions of the cargo container.

45. The method of claim 44, comprising scanning the entire cargo container with a pencil beam of radiation.

46. The method of claim 36, comprising scanning a cargo container having a width of at least about 1.5 meters.

47. A method of examining contents of an object, comprising:

moving the object along a first path;

moving at least one source of a radiation beam along a second path transverse to the first path to scan the object, the second path being within a first region extending partially around the first path; and

detecting radiation transmitted through the object by a stationary detector array, the detector array lying within a second region extending partially around the first path.

48. The method of claim 47, comprising reconstructing images based on the detected radiation.

49. The method of claim 48, comprising reconstructing computed tomography images based on the detected radiation.

50. The method of claim 47, comprising:

irradiating the object with a first radiation beam having a first energy distribution; and

irradiating the object with a second radiation beam having a second energy distribution different from the first energy distribution.

51. The method of claim 50, comprising:

detecting radiation transmitted through the object with a first, spatial detector array; and

detecting radiation transmitted through the object a second, energy sensitive, detector.

52. The method of claim 51, comprising:

reconstructing computed tomography images from the radiation detected by the first detector;

reconstructing images from the radiation detected by the second detector; and

fusing corresponding images from the radiation detected from the first and second detectors.

53. The method of claim 51, comprising:

detecting radiation from the first radiation beam transmitted through the object;

detecting radiation from the second radiation beam transmitted through the object;

computing a first value based on the detected radiation from the first radiation beam, for a plurality of voxels of the object;

computing a second value based on the detected radiation from the second radiation beam, for the plurality of voxels of the object;

processing the first and second values for the plurality of voxels; and

determining a material content of the plurality of voxels based on the processing.

55. The method of claim 47, further comprising:

identifying suspicious regions of the object;

then

irradiating the suspicious regions at a plurality of angles with a radiation beam from the at least one moving source;

detecting radiation caused by the interaction of the suspicious regions with the radiation beam; and

reconstructing computed tomography images of the suspicious regions from the detected radiation.

56. The method of claim 47, comprising moving a cargo container along the first path.

57. The method of claim 56, comprising supporting the cargo container on a truck.

58. The method of claim 47, further comprising generating a cone beam to scan the object.

54. The method of 53, comprising;

processing the first and second values by computing a ratio of the first and second values for the plurality of voxels; and

determining the material content of the plurality of voxels based on the ratio.

59. A method of examining contents of an object, comprising:

moving the object in a first direction;

irradiating the object with a plurality of cone beams of X-ray radiation, each cone beam being emitted from a respective one of a plurality of sources of X-ray radiation, the X-ray sources being arranged in a semi-circle lying on a first imaginary circle with a center within the cargo, the semi-circle being transverse to the first direction;

mechanically moving the plurality of X-ray sources about the semi-circle to irradiate the cargo with each cone beam at a plurality of angles, wherein the semi-circle lies on the first imaginary circle;

detecting radiation transmitted through the object by a semi-circular, stationary detector array comprising modules of two dimensional detectors, wherein the semi-circle lies on a second imaginary circle with a center within the object, the second imaginary circle lying in a same plane as the first imaginary circle; and

analyzing the detected radiation.

60. The method of claim 59, comprising reconstructing images based on the detected radiation.

61. The method of claim 60, comprising reconstructing computed tomography images based on the detected radiation.

62. The method of claim 59, comprising:

irradiating the object with a first radiation beam having a first energy distribution; and

irradiating the cargo with a second radiation beam having a second energy distribution different from the first energy distribution.

63. A scanning unit for examining a target, the scanning unit comprising:

a first path through the scanning unit to move the target;

a plurality of sources of beams of radiation, the plurality of sources being movable across a second path transverse to the first path;

a detector positioned to detect radiation transmitted through a target during scanning.

64. The scanning unit of claim 63, wherein the second path is within a first region extending partially around the first path.

65. The scanning unit of claim 63, wherein the detector is in a second region extending partially around the first path.

66. The scanning unit of claim 63, wherein the detector is stationary.

67. The scanning unit of claim 63, wherein the plurality of sources are sources of X-ray radiation.