Self-calibrated tomosynthetic, radiographic-imaging system, method, and device

• US 5,359,637 A
• Filed: 04/28/1992
• Issued: 10/25/1994
• Est. Priority Date: 04/28/1992
• Status: Expired due to Term

• Current Assignee: Wake Forest University Health Sciences
• Original Assignee: Wake Forest University
• Inventors: Webber, Richard L.
• Primary Examiner(s): Church, Craig E.
• Application Number:
  US07/875,249
• Time in Patent Office: 910 Days
• Field of Search: 378/2, 378/23, 378/162, 378/163
• US Class Current: 378/2
• CPC Class Codes: A61B 6/025 Tomosynthesis
• CPC Class Codes: A61B 6/4291 the detector being combined with a grid or grating
• CPC Class Codes: A61B 6/51 for dentistry

Abstract

A self-calibrating tomosynthetic x-ray system is provided. A calibrated device for recording radiographic images of a selected object irradiated by a source of radiation includes a first radiolucent radiographic recording medium in the form of a CCD device for recording a first projected radiographic image of the selected object. A second radiographic recording medium in the form of a CCD device is supported in fixed generally parallel position relative to the first radiographic recording medium to permit radiation from the source to pass through the first radiographic recording medium and to impinge upon the second radiographic recording medium for recording a second projected radiographic image of the selected object. A radiopaque fiducial reference in the form of a grid is supported in fixed position generally between the first and second radiographic recording mediums to permit a projected image of the radiopaque fiducial reference to be recorded on the second radiographic recording medium. Projected radiographic images of the object and the fiducial reference are then recorded at different arbitrary relative positions between the source of radiation and the object, the fiducial reference, and the recording mediums. An image of a selected object at a selected slice position through the object is synthesized from selected projected radiographic images of the object and the fiducial reference recorded by the calibrated device.

Claims

1. A system for synthesizing an image of a selected object at a selected slice position through the selected object from a plurality of projected radiographic images of the selected object comprising:

(a) at least one radiographic recording means for recording radiographic images of the selected object;

(b) at least one fiducial reference held in fixed position relative to the recording means;

(c) positioning means for holding the recording means and the fiducial reference in fixed position relative to the selected object;

(d) at least one source of radiation for irradiating the selected object to enable projected radiographic images of the object and the fiducial reference to be recorded on the recording means;

(e) position varying means for varying the relative positions between (1) the source of radiation and (2) the object, the fiducial reference and the recording means so that projected radiographic images of the object and the fiducial reference are recorded on the recording means at different arbitrary relative positions between (1) the source of radiation and (2) the object, the fiducial reference and the recording means; and

(f) an image synthesizer for synthesizing an image of the selected object at a selected slice position through the object from selected projections of the projected radiographic images of the object and the fiducial reference recorded on the recording means.

2. The system in accordance with claim 1 wherein the position varying means moves the object, the fiducial reference, and the recording means relative to the source of radiation.

3. The system in accordance with claim 2 wherein the position varying means includes a conveyer belt.

4. The system in accordance with claim 2 wherein the position varying means includes a rotatable turntable.

5. The system in accordance with claim 1 wherein the source of radiation includes a plurality of individual sources and said position varying means varies the relative positions by selectively activating said individual sources in an arbitrary manner.

6. The system in accordance with claim 1 wherein the image synthesizer includes:

(a) means for determining the location of the projected image of the fiducial reference at a plane at the recording means for each selected projection of images of the object and the fiducial reference recorded on the recording medium;

(b) means for selecting a reference location at the plane of the recording means;

(c) means for determining for each selected projection the distance and path of each projected image of the fiducial reference from the selected reference location;

(d) means for determining for each selected projection the respective location of the projected image of the fiducial reference at the selected slice position such that the position of the projected image of the fiducial reference for each selected projection will correspond to the selected reference location for a predetermined slice position through the fiducial reference; and

(e) means for shifting for each selected projection the projected image of the object and the fiducial reference recorded on the recording means to the selected slice position such that the projected image of the fiducial reference recorded on the recording means for each selected projection moves to its respective location at the selected slice position.

7. The system in accordance with claim 6 including means for spatially averaging the projected images of the object and the fiducial reference which have been shifted to the selected slice position.

8. The system in accordance with claim 6 wherein the reference location at the plane of the recording means is selected as the center of gravity of the projected images of the fiducial reference recorded on the recording means for the selected projections.

9. The system in accordance with claim 6 including means for determining the magnification of the projected image of the fiducial reference recorded on the recording means for each selected projection.

10. The system in accordance with claim 9 wherein the magnification is determined by comparing the size of the projected image of the fiducial reference recorded on the recording means relative to the actual size of the fiducial reference.

11. The system in accordance with claim 9 wherein the fiducial reference includes a frequency indicator for exhibiting a selected frequency pattern at the fiducial reference so that the projected image of the fiducial reference recorded on the recording means can exhibit a different frequency pattern relative to the frequency pattern exhibited at the fiducial reference and wherein the magnification is determined by comparing the frequency pattern exhibited by the projected image of the fiducial reference recorded on the recording means with respect to the frequency pattern exhibited at the fiducial reference.

12. The system in accordance with claim 11 wherein the frequency indicator includes a radiopaque grid.

13. The system in accordance with claim 9 including means for determining for each selected projection relative magnification of the projected image of the fiducial reference at the selected slice position on the basis of the determined magnification of the projected image of the fiducial reference recorded on the recording means.

14. The system in accordance with claim 13 including means for adjusting the magnification of the projected image of the object at the selected slice position on the basis of the determined relative magnification.

15. The system in accordance with claim 9 including means for determining for each selected projection relative displacement of the projected image of the fiducial reference at the selected slice position on the basis of the determined magnification of the projected image of the fiducial reference recorded on the recording means.

16. The system in accordance with claim 15 including means for adjusting the displacement of the projected image of the object at the selected slice position on the basis of the determined relative displacement.

17. A device for recording radiographic images of a selected object irradiated by a source of radiation comprising:

(a) a support;

(b) a first radiolucent radiographic recording medium supported relative to the support for recording a first projected radiographic image of the selected object;

(c) a second radiographic recording medium supported relative to the support in fixed position relative to the first radiographic recording medium and at a selected orientation relative to the first radiographic recording medium to permit radiation from the source of radiation to pass through the first radiographic recording medium and impinge upon the second radiographic recording medium for recording a second projected radiographic image of the selected object; and

(d) a radiopaque fiducial reference supported relative to the support at a fixed position generally between the first and second radiographic recording mediums to permit a projected radiographic image of the radiopaque fiducial reference to be recorded on the second radiographic recording medium, the radiopaque fiducial reference having a selected size and a selected position so that the projected image of the fiducial reference recorded on the second recording medium can exhibit a different size relative to the selected size of the reference and a displacement to a different position relative to the selected position of the fiducial reference.

18. The device in accordance with claim 17 wherein said indicator includes a frequency indicator for exhibiting a selected frequency pattern at the fiducial reference so that the projected image of the fiducial reference recorded on the second recording medium can exhibit a different frequency pattern relative to the selected frequency pattern at the fiducial reference and a phase shift relative to the selected frequency pattern at the fiducial reference.

19. The device in accordance with claim 18 wherein said frequency indicator includes a radiopaque grid.

20. The device in accordance with claim 19 wherein the first and second radiographic recording mediums and the radiopaque grid are positioned generally parallel with one another.

21. The device in accordance with claim 17 wherein each of the first and second radiographic recording mediums includes a CCD device.

22. An apparatus for tomosynthesis of multiple projected object images of a selected object comprising:

(a) an image detector positionable at a fixed position relative to the selected object for detecting said multiple protected object images, wherein said image detector includes a first image detecting medium for recording said multiple projected object images and a second image detecting medium supported in a fixed position at a selected angle of orientation relative to said first image detecting medium;

(b) a fiducial reference locatable at a fixed position relative to the selected object for producing multiple projected reference images on said image detector to yield composite images of said reference and object images detected upon said image detector, said second image detecting medium recording said composite images; and

(c) an image synthesizer for comparing parameters related to positions and sizes of reference images of said composite images detected upon said image detector to produce image translation data, and for reconstructing a tomographic slice from said composite images and said image translation data.

23. The apparatus of claim 22 wherein said fiducial reference is positioned between said first and second image detecting mediums.

24. The apparatus of claim 23 wherein said fiducial reference includes a reference frequency pattern indicator for providing a reference frequency pattern within said projected composite image so that said projected composite image received by said second image detecting medium exhibits a different frequency pattern and a phase shift relative to said reference frequency pattern.

25. The apparatus of claim 24 wherein said parameters related to positions and sizes of the reference images of said composite images detected upon said image detector include said different frequency pattern and said phase shift relative to said reference frequency pattern.

26. The apparatus of claim 24 wherein said reference frequency pattern indicator includes a grid.

27. A method for synthesizing an image of a selected object at a selected slice position through the selected object from a plurality of projected radiographic images of the selected object comprising:

(a) providing at least one radiographic recording means for recording radiographic images of the selected object;

(b) providing at least one fiducial reference in fixed position relative to the recording means;

(c) maintaining the selected object in fixed position relative to the recording means and the fiducial reference;

(d) providing at least one source of radiation for irradiating the selected object to enable projected radiographic images of the object and the fiducial reference to be recorded on the recording means;

(e) varying the relative positions between (1) the source of radiation and (2) the object, the fiducial reference and the recording means;

(f) recording projected radiographic images of the object and the fiducial reference on the recording means at different arbitrary relative positions between (1) the source of radiation and (2) the object, the fiducial reference and the recording means; and

(g) synthesizing an image of the selected object at a selected slice position through the object from selected recorded radiographic images of the object and the fiducial reference recorded on the recording means.

28. The method in accordance with claim 27 wherein the step of varying the relative positions between (1) the source of radiation and (2) the object, the fiducial reference, and the recording means includes moving the object, the fiducial reference, and the recording means relative to the source of radiation.

29. The method in accordance with claim 28 wherein the step of moving the object, the fiducial reference and the recording means relative to the source of radiation includes:

(a) maintaining the source of radiation in a fixed position; and

(b) placing the object, the fiducial reference and the recording means on a conveyer for moving the object, the fiducial reference and the recording means relative to the source of radiation.

30. The method in accordance with claim 29 wherein the conveyer includes a conveyer belt.

31. The method in accordance with claim 29 wherein the conveyer includes a rotatable turntable.

32. The method in accordance with claim 27 wherein the step of varying the relative positions between (1) the source of radiation and (2) the object, the fiducial reference, and the recording means includes moving the source of radiation relative to the object, the fiducial reference, and the recording means.

33. The method in accordance with claim 27 wherein the step of varying the relative positions between (1) the source of radiation and (2) the object, the fiducial reference, and the recording means includes varying the relative positions in an arbitrary manner.

48. The method in accordance with claim 27 wherein the radiographic recording means includes a CCD device.

49. The method in accordance with claim 27 wherein the step of synthesizing an image of the selected object at a selected slice position through the object includes:

(a) selecting the respective projections of images of the object and the fiducial reference recorded on the recording means for synthesizing the image at the selected slice;

(b) determining the location of the projected image of the fiducial reference at a plane at the recording means for each selected projection;

(c) selecting a reference location at the plane of the recording means;

(d) determining for each selected projection the distance and path of each projected image of the fiducial reference from the selected reference location;

(e) determining for each selected projection the respective location of the projected image of the fiducial reference at the selected slice position such that the position of the projected image of the fiducial reference for each selected projection will correspond to the selected reference location for a predetermined slice position through the fiducial reference; and

(f) shifting for each selected projection the projected image of the object and the fiducial reference recorded on the recording means to the selected slice position such that the projected image of the fiducial reference recorded on the recording means for each selected projection moves to its respective location at the selected slice position.

50. The method in accordance with claim 49 including spatially averaging the projected images of the object and the fiducial reference which have been shifted to the selected slice position.

51. The method in accordance with claim 50 including filtering the spatially averaged images.

52. The method in accordance with claim 49 wherein the reference location at the plane of the recording device is selected as the center of gravity of the projected images of the fiducial reference recorded on the recording means for the selected projections.

53. The method in accordance with claim 49 including determining the magnification of the projected image of the fiducial reference recorded on the recording means for each selected projection.

54. The method in accordance with claim 53 wherein the magnification is determined by comparing the size of the projected image of the fiducial reference recorded on the recording means relative to the actual size of the fiducial reference.

55. The method in accordance with claim 53 wherein the fiducial reference includes a frequency indicator for exhibiting a selected frequency pattern at the fiducial reference so that the projected image of the fiducial reference recorded on the recording means can exhibit a different frequency pattern relative to the frequency pattern exhibited at the fiducial reference and wherein the magnification is determined by comparing the frequency pattern exhibited by the projected image of the fiducial reference recorded on the recording means with respect to the frequency pattern exhibited at the fiducial reference.

56. The method in accordance with claim 55 wherein the frequency indicator includes a radiopaque grid.

57. The method in accordance with claim 53 including determining for each selected projection relative magnification of the projected image of the fiducial reference at the selected slice position based on the determined magnification of the projected image of the fiducial reference recorded on the recording means.

58. The method in accordance with claim 57 including for each selected projection adjusting the magnification of the projected image of the object at the selected slice position on the basis of the determined relative magnification.

59. The method in accordance with claim 53 including determining for each selected projection relative displacement of the projected image of the fiducial reference at the selected slice position on the basis of the determined magnification of the projected image of the fiducial reference recorded on the recording means.

60. The method in accordance with claim 59 including for each selected projection adjusting the displacement of the projected image of the object at the selected slice position on the basis of the determined relative displacement.

34. A method for synthesizing an image of a selected object at a selected slice position through the selected object from a plurality of projected radiographic images of the selected object comprising:

(a) providing at least one radiographic recording means for recording radiographic images of the selected object, the radiographic recording means including;

(i) a first radiographic recording medium for recording a projected radiographic image of the selected object; and

(ii) a second radiographic recording medium held in fixed position relative to the first radiographic recording medium and at a selected orientation relative to the first radiographic recording medium for recording a projected radiographic image;

(b) providing at least one fiducial reference in fixed position relative to the recording means, including providing said fiducial reference in fixed position relative to the first and second radiographic recording mediums to permit a projected image of the fiducial reference to be recorded on the second radiographic recording medium;

(c) maintaining the selected object in fixed position relative to the recording means and the fiducial reference;

(d) providing at least one source of radiation for irradiating the selected object to enable projected radiographic images of the object and the fiducial reference to be recorded on the recording means;

(e). varying the relative positions between (1) the source of radiation and (2) the object, the fiducial reference and the recording means;

(f) recording projected radiographic images of the object and the fiducial reference on the recording means at different arbitrary relative positions between (1) the source of radiation and (2) the object, the fiducial reference and the recording means; and

(g) synthesizing an image of the selected object at a selected slice position through the object from selected projected radiographic images of the object and the fiducial reference recorded on the recording means.

35. The method in accordance with claim 34 wherein the first radiographic recording medium is radiolucent and is positioned relative to the second radiographic recording medium to permit radiation from the source of radiation to pass through the first radiographic recording medium and to impinge upon the second radiographic recording medium.

36. The method in accordance with claim 35 wherein the first radiographic recording medium is positioned generally parallel to the second radiographic recording medium.

37. The method in accordance with claim 35 wherein the fiducial reference is positioned intermediate the first and second radiographic recording mediums.

38. The method in accordance with claim 34 wherein the first radiographic recording medium is radiolucent and is positioned relative to the second radiographic recording medium to permit radiation from the source of radiation to pass through the first radiographic recording medium and to impinge upon the second radiographic recording medium, and wherein the fiducial reference is positioned intermediate the first and second radiographic recording mediums to enable the first radiographic recording medium to record a first projected image of the selected object and to enable the second radiographic recording medium to record the projected image of the fiducial reference and a second projected image of the selected object.

39. The method in accordance with claim 38 wherein each of the first and second radiographic recording mediums includes a CCD device.

40. The method in accordance with claim 38 wherein the fiducial reference includes a radiopaque grid.

41. The method in accordance with claim 40 wherein the first and second recording mediums and the radiopaque grid are oriented generally parallel with one another.

42. The method in accordance with claim 34 wherein said fiducial reference includes a frequency indicator for exhibiting a selected frequency pattern at the fiducial reference so that the projected image of the fiducial reference can exhibit a different frequency pattern relative to the frequency pattern at the fiducial reference.

43. The method in accordance with claim 42 wherein said frequency indicator includes a radiopaque grid.

44. The method in accordance with claim 34 wherein said fiducial reference includes a frequency indicator for exhibiting a selected frequency pattern at the fiducial reference so that the projected image of the fiducial reference can exhibit a frequency pattern having a phase shift relative to the selected frequency pattern at the fiducial reference.

45. The method in accordance with claim 44 wherein said frequency indicator includes a radiopaque grid.

46. The method in accordance with claim 34 wherein the fiducial reference includes a displacement indicator at the fiducial reference for indicating a selected position of the fiducial reference so that the projected image of the fiducial reference can exhibit a displacement to a different position relative to the selected position of the displacement indicator of the fiducial reference.

47. The method in accordance with claim 34 wherein the fiducial reference includes a displacement indicator at the fiducial reference for indicating a selected size on the fiducial reference so that the projected image of the fiducial reference can exhibit a different size relative to the selected size of the displacement indicator of the fiducial reference.

61. A device for recording radiographic images of a selected object irradiated by a source of radiation comprising:

(a) a support;

(b) a first radiolucent radiographic recording medium supported on the support for recording a projected radiographic image of the selected object;

(c) a second radiographic recording medium supported relative to the support in fixed position relative to the first radiographic recording medium to permit radiation from the source of radiation to pass through the first radiographic recording medium and impinge upon the second radiographic recording medium; and

(d) a radiopaque fiducial reference supported relative to the support at a fixed position intermediate the first and second radiographic recording mediums to permit a projected radiographic image of the radiopaque fiducial reference to be recorded on the second radiographic recording medium.

62. A system for synthesizing an image of a selected object at a selected slice position through the selected object from a plurality of projected radiographic images of the selected object comprising:

(a) at least one radiographic recording means for recording radiographic images of the selected object, wherein the radiographic recording means includes;

(i) a first radiographic recording medium for recording a projected radiographic image of the selected object; and

(ii) a second radiographic recording medium held in fixed position relative to the first radiographic recording medium and at a selected orientation relative to the first radiographic recording medium for recording a projected radiographic image;

(b) at least one fiducial reference held in fixed position relative to the recording means, wherein said fiducial reference is held in fixed position relative to the first and second radiographic recording mediums to permit a projected image of the fiducial reference to be recorded on the second radiographic recording medium;

(c) positioning means for holding the recording means and the fiducial reference in fixed position relative to the selected object;

(d) at least one source of radiation for irradiating the selected object to enable projected radiographic images of the object and the fiducial reference to be recorded on the recording means;

(e) position varying means for varying the relative positions between (1) the source of radiation and (2) the object, the fiducial reference and the recording means so that projected radiographic images of the object and the fiducial reference are recorded on the recording means at different arbitrary relative positions between (1) the source of radiation and the object, the fiducial reference and the recording means; and

(f) an image synthesizer for synthesizing an image of the selected object at a selected slice position through the object from selected projections of the projected radiographic images of the object and the fiducial reference recorded on the recording means.

63. The system in accordance with claim 62 wherein the fiducial reference includes a displacement indicator at the fiducial reference for indicating a selected size of the fiducial reference so that the projected image of the fiducial reference can exhibit a different size relative to the selected size of the displacement indicator of the fiducial reference.

64. The system in accordance with claim 62 wherein said fiducial reference includes a frequency indicator for exhibiting a selected frequency pattern at the fiducial reference so that the projected image of the fiducial reference can exhibit a frequency pattern having a phase shift relative to the selected frequency pattern at the fiducial reference.

65. The system in accordance with claim 62 wherein the fiducial reference includes a displacement indicator at the fiducial reference for indicating a selected position of the fiducial reference so that the projected image of the fiducial reference can exhibit a displacement to a different position relative to the selected position of the displacement indicator of the fiducial reference.

66. The system in accordance with claim 62 wherein said radiopaque fiducial reference includes a frequency indicator for exhibiting a selected frequency pattern at the fiducial reference so that the projected image of the fiducial reference can exhibit a different frequency pattern relative to the frequency pattern at the fiducial reference.

67. The system in accordance with claim 62 wherein the first radiographic recording medium is radiolucent and is positioned relative to the second radiographic recording medium to permit radiation from the source of radiation to pass through the first radiographic recording medium and to impinge upon the second radiographic recording medium, and wherein the fiducial reference is positioned intermediate the first and second radiographic recording mediums to enable the first radiographic recording medium to record a first projected image of the selected object and to enable the second radiographic recording medium to record the projected image of the fiducial reference and a second projected image of the selected object.

68. The system in accordance with claim 67 wherein each of the first and second radiographic recording mediums includes a CCD device.

69. The system in accordance with claim 67 wherein the fiducial reference includes a radiopaque grid and wherein the first and second recording mediums and the radiopaque grid are oriented generally parallel with one another.