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

• US 5,668,844 A
• Filed: 10/20/1994
• Issued: 09/16/1997
• 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:
  US08/326,332
• Time in Patent Office: 1,062 Days
• Field of Search: 378/2, 378/23, 378/162, 378/163, 378/164
• 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 device for recording radiographic images of a selected object irradiated by a source of radiation comprising:

(a) a support;

(b) a first 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 and at a selected orientation relative to the first radiographic recording medium for recording a projected radiographic image; and

(d) a radiopaque fiducial reference supported relative to the support at a fixed position relative to 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 wherein the fiducial reference includes a frequency indicator for exhibiting a selected frequency pattern at the fiducial reference.

2. The device in accordance with claim 1 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 impinge upon the second radiographic recording medium.

3. The device in accordance with claim 2 wherein the first radiographic recording medium is positioned generally parallel to the second radiographic recording medium.

4. The device in accordance with claim 3 wherein the radiopaque fiducial reference is positioned intermediate the first and second radiographic recording mediums.

5. The device in accordance with claim 1 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 impinge upon the second radiographic recording medium and wherein the radiopaque 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 radiopaque fiducial reference and a second projected image of the selected object.

6. The device in accordance with claim 5 wherein each of the first and second radiographic recording mediums includes a CCD device.

7. The device in accordance with claim 5 wherein said radiopaque fiducial reference includes a radiopaque grid.

8. The device in accordance with claim 7 wherein the first and second recording mediums and the radiopaque grid are oriented generally parallel with one another.

9. The device in accordance with claim 8 wherein each of the first and second radiographic recording mediums includes a CCD device.

10. The device in accordance with claim 1 wherein said frequency indicator exhibits a selected frequency pattern at thhe fiducial reference so that the projected image of the fiducial reference can exhibit a different frequency pattern relative to the frequency pattern exhibited at the fiducial reference.

11. The device in accordance with claim 10 wherein said frequency indicator includes a radiopaque grid.

12. The device in accordance with claim 1 wherein said frequency indicator exhibits 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.

13. The device in accordance with claim 12 wherein said frequency indicator includes a radiopaque grid.

14. The device in accordance with claim 1 wherein the radiopaque 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.

15. The device in accordance with claim 1 wherein the radiopaque 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.

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

(a) an image detector positioned at a fixed position relative to the selected object for detecting said multiple object images;

(b) a fiducial reference positioned at a fixed position relative to the selected object for producing multiple reference images on said image detector to yield composite images of said reference and object images detected upon said image detector; and

(c) an image synthesizer for analyzing 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.

17. The apparatus of claim 16 wherein said fiducial reference includes a metallic bead.

18. The apparatus of claim 16 wherein said image detector includes a CCD device.

19. The apparatus of claim 16 wherein said image detector includes first image detecting medium for recording said multiple 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 for recording said composite images.

20. The apparatus of claim 19 wherein said fiducial reference is positioned between said first and second image detecting mediums.

21. The apparatus of claim 20 wherein said fiducial reference includes a reference frequency pattern for providing a reference frequency pattern image within said composite image so that said reference frequency pattern image recorded by said second image detecting medium can exhibit a different frequency pattern and a phase shift relative to said reference frequency pattern.

22. The apparatus of claim 21 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.

23. The apparatus of claim 21 wherein said reference frequency pattern includes a grid.

24. A system for tomosynthesis of multiple projected object images of a selected object comprising:

(a) an image detector for detecting multiple projected object images at different relative positions to the selected object;

(b) a fiducial reference located at a fixed reference position relative to the selected object for producing multiple projected reference images upon said image detector; and

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

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

(a) providing at least one recording means for recording 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 imaging source for producing images of the object and the fiducial reference to be recorded on the recording means;

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

(f) recording images of the object and the fiducial reference on the recording means at different arbitrary relative positions between (1) the imaging source 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 images of the object and the fiducial reference recorded on the recording means.

26. The method in accordance with claim 25 wherein the step of varying the relative positions between (1) the imaging source 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 imaging source.

27. The method in accordance with claim 26 wherein the step of moving the object, the fiducial reference and the recording means relative to the imaging source includes:

(a) maintaining the imaging source 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 imaging source.

28. The method in accordance with claim 26 wherein the step of varying the relative positions between (1) the imaging source and (2) the object, the fiducial reference, and the recording means includes varying the relative positions in an arbitrary manner.

29. The method in accordance with claim 25 wherein the imaging source includes a source of x-ray radiation.

30. The method in accordance with claim 25 wherein the step of varying the relative positions between (1) the imaging source and (2) the object, the fiducial reference, and the recording means includes moving the imaging source relative to the object, the fiducial reference, and the recording means.

31. The method in accordance with claim 25 wherein the step of varying the relative positions between (1) the imaging source an (2) the object, the fiducial refrence, and the recording means includes varying the relative positions in an arbitrary manner.

32. The method in accordance with claim 25 wherein the step of synthesizing an image of the selected object at a selected slice position through the object includes:

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

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

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

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

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

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

33. The method in accordance with claim 32 including spatially averaging the images of the object and the fiducial reference which have been shifted to the selected slice position.

34. The method in accordance with claim 33 including filtering the spatially averaged images.

35. The method in accordance with claim 32 wherein the reference location at the plane of the recording device is selected as the center of gravity of the images of the fiducial reference recorded on the recording means for the selected recordings.

36. The method in accordance with claim 32 including determining for each selected recording relative displacement of the image of the fiducial reference at the selected slice position.

37. The method in accordance with claim 36 including for each selected recording adjusting the displacement of the image of the object at the selected slice position on the basis of the determined relative displacement.

38. The method in accordance with claim 32 including determining for each selected recordings the magnification of the image of the fiducial reference recorded on the recording means.

39. The method in accordance with claim 38 wherein the magnification is determined by comparing the size of the image of the fiducial reference recorded on the recording means relative to the actual size of the fiducial reference.

40. The method in accordance With claim 38 wherein the fiducial reference includes a frequency indicator for exhibiting a selected frequency pattern at the fiducial reference so that the 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 image of the fiducial reference recorded on the recording means with respect to the frequency pattern exhibited at the fiducial reference.

41. The method in accordance with claim 40 wherein the frequency indicator includes a grid.

42. The method in accordance with claim 38 including determining for each selected recording relative magnification of the image of the fiducial reference at the selected slice position based on the determined magnification of the image of the fiducial reference recorded on the recording means.

43. The method in accordance with claim 42 including for each selected recording adjusting the magnification of the image of the object at the selected slice position on the basis of the determined relative magnification.

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

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

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

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

(d) at least one imaging source for producing 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 imaging source and (2) the object, the fiducial reference and the recording means so that images of the object and the fiducial reference are recorded on the recording means at different arbitrary relative positions between (1) the imaging source 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 recordings of the images of the object and the fiducial reference recorded on the recording means.

45. The system in accordance with claim 44 wherein the position varying means moves the object, the fiducial reference, and the recording means relative to the imaging source.

46. The system in accordance with claim 45 wherein the position varying means includes a conveyer belt.

47. The system in accordance with claim 44 wherein the imaging source includes a source of radiation.

48. The system in accordance with claim 44 wherein the position varying means varies the relative positions in an arbitrary manner.

49. The system.in accordance with claim 44 wherein the image synthesizer includes:

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

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

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

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

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

50. The system in accordance with claim 49 including means for spatially averaging the images of the object which have been shifted to the selected slice position.

51. The system in accordance with claim 49 wherein the reference location at the plane of the recording means is selected as the center of gravity of the images of the fiducial reference recorded on the recording means for the selected recordings.

52. The system in accordance with claim 49 including means for determining the magnification of the image of the fiducial reference recorded on the recording means for each selected recording.

53. The system in accordance with claim 52 wherein the magnification is determined by comparing the size of the image of the fiducial reference recorded on the recording means relative to the actual size of the fiducial reference.

54. The system in accordance with claim 52 wherein the fiducial reference includes a frequency indicator for exhibiting a selected frequency pattern at the fiducial reference so that the image of the fiducial reference recorded on the recording means can exhibit 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 image of the fiducial reference recorded on the recording means with respect to the frequency pattern exhibited at the fiducial reference.

55. The system in accordance with claim 54 wherein the frequency indicator includes a grid.

56. The system in accordance with claim 52 including means for determining for each selected recording relative magnification of the image of the fiducial reference at the selected slice position on the basis of the determined magnification of the image of the fiducial reference recorded on the recording means.

57. The system in accordance with claim 56 including means for adjusting the magnification of the image of the object at the selected slice position on the basis of the determined relative magnification.

58. The system in accordance with claim 49 including means for determining for each selected recording relative displacement of the image of the fiducial reference at the selected slice position.

59. The system in accordance with claim 58 including means for adjusting the displacement of the image of the object at the selected slice position on the basis of the determined relative displacement.

60. A system for synthesizing a tomographic image of a selected object at a selected slice position through the selected object, the system comprising:

(a) a fiducial reference held in a fixed-position relative to the selected object;

(b) an image projector for projecting object images of the selected object and reference images of said fiducial reference;

(c) an image detector located at a fixed position relative to the selected object for detecting said object images and said reference images projected by the image projector; and

(d) an image synthesizer for comparing parameters related to positions and sizes of reference images detected upon said image detector to parameters of the fiducial reference to produce image translation data, and for reconstructing the tomographic image from said object images and said image translation data.

61. The system of claim 60 wherein said parameters related to positions and sizes of the reference images detected upon said image detector include a frequency pattern and a phase shift of said detected reference images.

62. The system of claim 60 wherein said image projector comprises a source of radiation.

63. The system of claim 60 wherein said image detector is located for detecting composite images of said object images and said reference images projected by the image projector and wherein said image synthesizer compares parameters related to positions and sizes of the reference images within the composite images to parameters of the fiducial reference to produce the image translation data and wherein the image synthesizer reconstructs the tomographic image from said composite images and said image translation data.

64. A method of tomosynthesis of projected images of a selected object comprising the steps of:

(a) positioning a fiducial reference at a fixed position relative to the selected object;

(b) projecting object images of the selected object and reference images of the fiducial reference;

(c) detecting said projected object images and said projected reference images at a fixed location relative to the selected object to produce image data;

(d) comparing parameters related to positions and sizes of the detected reference images to parameters of the fiducial reference to produce image translation data; and

(e) reconstructing a tomographic slice of the selected object from said image translation data and said image data.

65. The method of claim 64 wherein the step of projecting object images and reference images includes projecting composite images of the object images and the reference images and wherein the step of detecting said projected object images and said projected reference images includes detecting said composite images to produce composite image data and wherein the step of reconstructing a tomographic slice includes reconstructing a tomographic slice from said image translation data and said composite image data.