X-ray backscatter imaging system including moving body tracking assembly

• US 6,094,472 A
• Filed: 04/14/1998
• Issued: 07/25/2000
• Est. Priority Date: 04/14/1998
• Status: Expired due to Term

• Current Assignee: Rapiscan Systems Incorporated (OSI Systems Incorporated)
• Original Assignee: Rapiscan Security Products USA Incorporated (OSI Systems Incorporated)
• Inventors: Smith, Steven W.
• Primary Examiner(s): Porta, David P.
• Assistant Examiner(s): Dunn, Drew A.
• Application Number:
  US09/060,009
• Time in Patent Office: 833 Days
• Field of Search: 378/57, 378/86, 378/87, 378/88
• US Class Current: 378/86
• CPC Class Codes: G01N 23/203 Measuring back scattering
• CPC Class Codes: G01V 5/22 Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays
• CPC Class Codes: G01V 5/222 measuring scattered radiation

Abstract

A pencil beam of X-rays is scanned over the surfaces of the body of a person being examined as the person walks through the scanning apparatus. Specifically, a tracking assembly is employed to rotate the scanning plane through a tracking angle and in a direction progressing from the entrance to the exit of the portal, through which the person passes, in order to substantially track the person or body as it moves with respect to the system from the entrance to the exit X-rays that are scattered or reflected from the subject'"'"'s body are detected by a detector assembly. The signal produced by this scattered X-ray detector in then used to modulate an image display device to produce an image of the subject and any concealed objects carried by the subject. The detector assembly is constructed in a configuration to automatically and uniformly enhance the image edges of low atomic number (low Z) concealed objects to facilitate their detection. A storage means is provided by which previously acquired images can be compared with the present image for analyzing variances in and similarities with the present image, and provides means for creating a generic representation of the body being examined while suppressing anatomical features of the subject to minimize invasion of the subject'"'"'s privacy.

Claims

1. X-ray imaging apparatus for detecting an object carried by or on a body moving relative to the apparatus, said apparatus having an entrance and an exit, said apparatus comprising:

a passageway extending at least from said entrance to said exit;

at least one X-ray source having means for producing a pencil beam of X-rays directed toward said body in said passageway, said pencil beam intersecting said body at a region of intersection corresponding to a pixel having a pixel value;

a scanning means disposed adjacent said at least one X-ray source for moving the region of intersection of said pencil beam and said body over a surface of said body;

a tracking means for causing the scanning means to substantially track said body as it moves with respect to said apparatus from said entrance to said exit;

a detector assembly for detecting an intensity of X-rays scattered from said body as a result of being scanned by said first scanning means and for generating a signal representative of the intensity of the scattered X-rays, said detector assembly comprising a plurality of detectors; and

display means for presenting characteristics of the detector signal to an operator.

2. The X-ray imaging apparatus of claim 1, wherein said passageway comprises a left side and a right side relative to said body as said body moves between said left side and said right side of said passageway from said entrance to said exit, and wherein said at least one X-ray source comprises a first X-ray source disposed within said left side and a second X-ray source disposed within said right side.

3. The X-ray imaging apparatus as in claim 2, wherein said first X-ray source and said second X-ray source are disposed offset from each other along said passageway for scanning said subject from a plurality of angles.

4. The X-ray imaging apparatus as in claim 3, wherein said first X-ray source and said second X-ray source operate sequentially for providing a plurality of scans in a succession, said plurality of scans producing a plurality of images of said body at said plurality of angles.

5. The X-ray imaging apparatus of claim 4, wherein the plurality of images comprises four images.

6. The X-ray imaging apparatus of claim 2, wherein said plurality of detectors comprises a first array of detectors corresponding to said left side of said passageway and a second array of detectors corresponding to said right side of said passageway.

7. The X-ray imaging apparatus of claim 2, wherein said passageway further comprises a ceiling, wherein at least one detector of said plurality of detectors is disposed in said ceiling.

8. The X-ray imaging apparatus of claim 6, wherein said first X-ray source is disposed within said first array of detectors and said second X-ray source is disposed within said second array of detectors.

9. The X-ray imaging apparatus of claim 8, wherein each of said first X-ray source and said second X-ray source is disposed at a height generally corresponding to a mid-torso height of the body.

10. The X-ray imaging apparatus of claim 1, wherein each detector of said plurality of detectors comprises a fluorescent screen having a persistence of less that about 10 microseconds.

11. The X-ray imaging apparatus of claim 10, wherein said fluorescent screen is made from barium lead sulfate.

12. The X-ray imaging apparatus of claim 10, wherein said fluorescent screen is made from barium strontium sulfate.

13. The X-ray imaging apparatus of claim 1, wherein said tracking means comprises means for horizontally sweeping said scanning means.

14. The X-ray imaging apparatus of claim 13, wherein said means for horizontally sweeping comprises a turntable assembly for rotating said scanning means about a vertical axis.

15. The X-ray imaging apparatus of claim 13, wherein said means for horizontal sweeping comprises a horizontal axis disposed above said passageway, wherein said scanning means pivots on said horizontal axis.

16. The X-ray imaging apparatus of claim 13, wherein said means for horizontal sweeping comprises a horizontal beam disposed above said passageway and at least one slide means connected to said horizontal beam for sliding said scanning means within a horizontal plane.

17. The X-ray imaging apparatus of claim 1, wherein said at least one X-ray source comprises a first X-ray source and a second X-ray source, said first X-ray source and said second X-ray source each having a corresponding scanning means, wherein said tracking means comprises:

a pair of offset mountings for mounting said first X-ray source and its corresponding first scanning means near said entrance and said second X-ray source and its corresponding first scanning means near said exit so that each of said first X-ray source and said second X-ray source is positioned to project said pencil beam substantially toward a longitudinal center portion of said passageway between said entrance and said exit; and

a sequential timer for sequentially activating said first X-ray source and said second X-ray source as said body moves within said passageway.

18. The X-ray imaging apparatus of claim 17, wherein said passageway includes a plurality of turns therein.

19. The X-ray imaging apparatus of claim 1, wherein said at least one X-ray source comprises four X-ray sources, one X-ray source corresponding to one of four images.

20. The X-ray imaging apparatus of claim 19, wherein said tracking means comprises a timing device for sequentially activating said four X-ray sources one at a time as the body progresses through the passageway.

21. The X-ray imaging apparatus of claim 1, wherein said scanning means comprises a chopper assembly for vertically translating said pencil beam over a length of said body.

22. The X-ray imaging apparatus as in claim 21, wherein said scanning means further comprises a means for horizontally moving said pencil beam over a width of said body.

23. The X-ray imaging apparatus of claim 1, further comprising at least one sensor for sensing movement of said body with respect to said apparatus and generating a motion signal in response thereto.

24. The X-ray imaging apparatus of claim 23, wherein said tracking means is responsive to said motion signal.

25. The X-ray imaging apparatus of claim 1, further comprising a mechanical means for moving said body through said passageway.

26. The X-ray imaging apparatus of claim 25, wherein the mechanical means for moving said body comprises a moving walkway.

27. The X-ray imaging apparatus of claim 1, wherein said at least one X-ray source comprises an X-ray tube operating at a potential of 70 KV at 10 ma.

28. The X-ray imaging apparatus of claim 1, wherein each pixel has an area on the order of 15 square millimeters.

29. In an X-ray backscatter imaging system for searching a subject for concealed objects, a method comprising the steps of:

moving the subject within a passageway, the passageway having an entrance and an exit;

initiating operation of at least one X-ray source upon entry of the subject into the passageway;

producing a pencil beam of X-rays having a low dose directed toward a scanning area at a plurality of scanning positions within the passageway;

scanning the pencil beam of X-rays over the scanning area;

tracking said pencil beam of X-rays to each of said plurality of scanning positions, wherein the tracking is substantially coordinated with forward progress of the subject through the passageway;

using a plurality of detectors, detecting X-rays that are backscattered from said pencil beam as a result of interacting with the subject when positioned at each scanning position of the plurality of scanning positions; and

displaying a digitally represented image of the detected backscattered X-rays.

30. The method of claim 29, wherein said step of scanning comprises chopping the pencil beam of X-rays using a rotating chopper.

31. The method of claim 30, wherein the step of tracking comprises rotating an X-ray source and the rotating chopper on a turntable disposed at a side of the passageway.

32. The method of claim 29, wherein the step of tracking comprises pivoting an X-ray source and the rotating chopper on a horizontal axis disposed above the passageway.

33. The method of claim 29, wherein the step of tracking is coordinated with the movement of the subject by sequentially activating a plurality of X-ray sources, each X-ray source generating a different vertically-scanned pencil beam of X-rays.

34. The method of claim 33, wherein the plurality of X-ray sources comprises two X-ray sources disposed on opposite sides of the passageway.

35. The method of claim 34, wherein the step of sequentially activating the two X-ray sources includes separately activating each X-ray source as the subject approaches a longitudinal center of the passageway and as the subject moves away from the longitudinal center of the passageway so that four scanning positions are defined.

36. The method of claim 33, wherein the plurality of X-ray sources comprises two X-ray sources disposed on opposite ends of the passageway.

37. The method of claim 36, wherein the step of sequentially activating the two X-ray sources includes separately activating a first X-ray source as the subject approaches a longitudinal center of the passageway and a second X-ray source as the subject moves away from the longitudinal center of the passageway so that at least two scanning positions are defined.

38. The method of claim 29, wherein the plurality of detectors comprises detector arrays, one detector array disposed in opposite sides of the passageway.

39. The method of claim 29, further comprising sensing a presence of the subject at an entrance of the passageway and generating an initiation signal to the imaging system.

40. An X-ray imaging system for detecting an object carried by or on a body, said system having an entrance and an exit, said system comprising:

a passageway extending from said entrance to said exit;

at least one X-ray source for producing a pencil beam of X rays directed toward said body in said passageway, said at least one X-ray source comprising a collimator mechanism for scanning said pencil beam in a parallel beam plane;

a scanning assembly for scanning said parallel beam plane over a surface of said body as said body moves in a direction of movement from said entrance to said exit;

a tracking assembly for causing said scanning assembly to substantially track said body as it moves with respect to said system from said entrance to said exit;

a detector array for detecting an intensity of X-rays scattered from said body and for generating a detector signal representative of an intensity of said scattered X-rays, said detector array comprising at least one detector; and

a processor assembly for presenting characteristics of said detector signal to an operator, and for controlling said X-ray source, said scanning assembly, said tracking assembly, and said detector array.

41. The X-ray imaging system of claim 40, wherein said passageway comprises a left side and a right side with respect to said body as said body moves through said passageway, and wherein said at least one X-ray source comprises a first X-ray source disposed within said left side and a second X-ray source disposed within said right side.

42. The X-ray imaging system as in claim 41, wherein said first X-ray source and said second X-ray source are disposed offset from each other along said passageway for scanning said subject from a plurality of angles.

43. The X-ray imaging system as in claim 42, wherein said first X-ray source and said second X-ray source operate sequentially for providing a plurality of scans in a succession, said plurality of scans producing a plurality of images of said body at said plurality of angles.

44. The X-ray imaging system of claim 43, wherein said plurality of images comprises a left front image, a left rear image, a right front image, and a right rear image of said body.

45. The X-ray imaging system of claim 41, wherein said detector array comprises a first array of detectors corresponding to said left side of said passageway and a second array of detectors corresponding to said right side of said passageway.

46. The X-ray imaging system of claim 45, wherein said passageway further comprises a ceiling.

47. The X-ray imaging system of claim 46, wherein said detector array further comprises at least one ceiling detector disposed in said ceiling.

48. The X-ray imaging system of claim 40, wherein said at least one detector comprises a fluorescent screen having a persistence of less that about 10 microseconds.

49. The X-ray imaging system of claim 48, wherein said fluorescent screen is made from barium lead sulfate.

50. The X-ray imaging system of claim 48, wherein said fluorescent screen is made from barium strontium sulfate.

51. The X-ray imaging system of claim 40, wherein said parallel beam plane is a vertical beam plane over a length of said body.

52. The X-ray imaging system as in claim 51, wherein said scanning assembly horizontally sweeps said vertical beam plane over a width of said body.

53. The X-ray imaging system of claim 52, wherein said tracking assembly comprises a turntable assembly for rotating said vertical beam plane about a vertical axis.

54. The X-ray imaging system of claim 40, wherein said at least one X-ray source comprises an overhead X-ray source disposed above said passageway.

55. The X-ray imaging system of claim 54, wherein said tracking assembly causes said scanning assembly to pivot said parallel beam plane about a horizontal axis, said parallel beam plane tracking said body along to said direction of movement.

56. The X-ray imaging system of claim 40, wherein said passageway includes a plurality of turns therein.

57. The X-ray imaging system of claim 40, wherein said at least one X-ray source comprises four X-ray sources, one X-ray source corresponding to one of four images.

58. The X-ray imaging system of claim 57, further comprising a timing device for sequentially activating said four X-ray sources one at a time as said body progresses through said passageway.

59. The X-ray imaging system of claim 40, further comprising at least one sensor for sensing movement of said body with respect to said system and for generating a motion signal in response thereto.

60. The X-ray imaging system of claim 59, wherein said processor assembly utilizes said motion signal for controlling said X-ray imaging system.

61. The X-ray imaging system of claim 40, further comprising a mechanical assembly for moving said body through said passageway.

62. The X-ray imaging system of claim 61, wherein said mechanical assembly for moving said body comprises a moving walkway.

63. The X-ray imaging system of claim 40, wherein said at least one X-ray source comprises an X-ray tube operating at a potential of 70 KV at 10 ma.

64. The X-ray imaging system of claim 40, wherein said pencil beam has a cross-sectional area corresponding to a pixel a point where said pencil beam intersects said body, said pixel having an area on the order of 15 square millimeters.

65. The X-ray imaging system of claim 40, wherein said processor assembly comprises a monitor screen for displaying an image representative of said body.

66. The X-ray imaging system of claim 40, wherein said detector array further comprises at least one transmission detector.

67. An apparatus for detecting an object carried by or on a body, said apparatus comprising:

a flooring having a length, said body moving across said flooring in a direction of movement;

at least one X-ray source positioned above said flooring and at a height sufficient to allow said body to pass below said at least one X-ray source, said at least one X-ray source emitting an X-ray pencil beam scanned in a horizontal plane to produce a horizontal beam plane, said horizontal beam plane directed toward said body;

a tracking assembly for rotating said horizontal beam plane through a tracking angle and in a direction corresponding to said direction of movement, wherein a starting portion of said tracking angle directs said horizontal beam plane to a front area of said body, and an ending portion of said tracking angle directs said horizontal beam plane to a back area of said body;

a detector array disposed in said flooring and positioned along said length, said detector array comprising at least one scatter detector for detecting an intensity of X-rays scattered from said body and for generating a detector signal representative of the intensity of the scattered X-rays; and

a processor assembly for controlling said apparatus, said processor comprising an interface for presenting a representation of said detector signal to an apparatus operator.

68. The apparatus as in claim 67, wherein said detector array further comprises at least one transmission detector disposed adjacent said at least one scatter detector.

69. The apparatus as in claim 68, wherein said at least one scatter detector comprises a plurality of scatter detectors, and said at least one transmission detector comprising a plurality of transmission detectors, wherein said plurality of transmission detectors is dispersed among said plurality of scatter detectors.

70. The apparatus as in claim 67, further comprising at least one sensor for sensing movement of said body along said length of said flooring and for generating a motion signal in response thereto.

71. The apparatus as in claim 70, wherein said processor assembly utilizes said motion signal for controlling said at least one X-ray source and said tracking assembly.

72. The apparatus as in claim 67, wherein said flooring further comprises a mechanical assembly for moving said body in said direction of movement.

73. The apparatus as in claim 72, wherein said mechanical assembly for moving said body comprises a moving walkway.

74. An X-ray imaging system for detecting concealed objects on a body, said body having a body front, a body back, and body sides, said system comprising:

a portal structure comprising a first side module, a second side module, and a ceiling module, said first side module and said second side module parallel and separated by a portal width, said ceiling module positioned above said first side module and said second side module to form a portal having an entrance and an exit;

a detector array for producing a detector signal from scattered X-rays, said detector array having a first side detector array concealed within said first side module and a second side detector array concealed within said second side module;

an X-ray source for emitting a pencil beam of X-rays scanned across a scanning plane, said X-ray source concealed within said ceiling module, said scanning plane directed toward said exit and at a downward angle;

a tracking assembly for rotating said scanning plane through a tracking angle and in a direction progressing from said entrance to said exit to substantially track said body as it moves with respect to said system from said entrance to said exit; and

a display means for presenting characteristics of said detector signal;

wherein said body moves through said scanning plane as said body moves from said entrance to said exit, said pencil beam of X-rays of said scanning plane striking said body front and producing said scattered X-rays.

75. The X-ray imaging system as in claim 74, wherein said downward angle is a 45 degree angle.

76. The X-ray imaging system as in claim 74, further comprising a second X-ray source for emitting a second pencil beam of X-rays scanned across a second scanning plane, said second X-ray source located in said ceiling and directed toward said entrance at a second downward angle, wherein said scanning plane strikes said body back as said body moves from said entrance to said exit.

77. The X-ray imaging system as in claim 76, wherein said second downward angle is a 45 degree angle.

78. The X-ray imaging system as in claim 76, wherein said X-ray source and said second X-ray source alternately emit said first scanning plane and said second scanning plane.

79. The X-ray imaging system as in claim 74, further comprising a first transmission detector located in said first side module, and a second transmission detector located in said second side module, said first and second transmission detectors for detecting transmitted X-rays, and for producing a transmission detector signal for detecting said concealed objects on said body sides.

80. The X-ray imaging system as in claim 79, wherein said first and second transmission detectors are positioned at said downward angle.

81. The X-ray imaging system as in claim 76, further comprising a plurality of transmission detectors for detecting transmitted X-rays, and for producing a transmission detector signal for detecting said concealed objects on said body sides.

82. The X-ray imaging system as in claim 81, wherein a first and second transmission detector of said plurality of transmission detectors is located in said first side module and said second side module respectively, and wherein said first and second transmission detectors are positioned at said downward angle.

83. The X-ray imaging system as in claim 82, wherein a third and fourth transmission detector of said plurality of transmission detectors is located in said first side module and said second side module respectively, and wherein said third and fourth transmission detectors are positioned at said second downward angle.