Method and software for improving coronary calcium scoring consistency

• US 20030095693A1
• Filed: 04/18/2002
• Published: 05/22/2003
• Est. Priority Date: 11/20/2001
• Status: Active Grant

• Current Assignee: Merge Healthcare Solutions Incorporated (International Business Machines Corporation)
• Original Assignee: AccuImage Diagnostics Corp. (International Business Machines Corporation)
• Inventors: Kaufman, Leon, Carlson, Joseph W.
• Granted Patent: US 7,127,096 B2
• Time in Patent Office: Days
• US Class Current: 382/128
• CPC Class Codes: A61B 6/027 characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral
• CPC Class Codes: A61B 6/5288 involving retrospective matching to a physiological signal
• CPC Class Codes: A61B 6/541 involving acquisition triggered by a physiological signal
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: G06T 2207/10081 Computed x-ray tomography [CT]
• CPC Class Codes: G06T 2207/20008 Globally adaptive
• CPC Class Codes: G06T 2207/20056 Discrete and fast Fourier transform, [DFT, FFT]
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 2207/30101 Blood vessel; Artery; Vein; Vascular
• CPC Class Codes: G06T 5/10 using non-spatial domain filtering
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: G06T 5/73 Deblurring; Sharpening
• CPC Class Codes: G06V 10/30 Noise filtering
• CPC Class Codes: G16H 30/40 for processing medical images, e.g. editing
• CPC Class Codes: G16H 40/40 for the management of medical equipment or devices, e.g. scheduling maintenance or upgrades
• CPC Class Codes: G16H 40/67 for remote operation

Abstract

Methods and devices for improving the machine-to-machine and temporal (e.g., inter and intra-machine) and database consistency of coronary calcium scoring by applying a filtering algorithm that sharpens and/or smoothes the image so as to return a filtered image having a spatial resolution of a certain reference value.

Claims

1. A method of improving the consistency of coronary calcium scoring, the method comprising:

imaging a phantom with an imaging device;

measuring a spatial resolution from the image of the phantom;

comparing the measured spatial resolution of the image of the phantom against a reference spatial resolution;

choosing a filter algorithm that will alter the spatial resolution of the image of the phantom to substantially match the reference spatial resolution; and

applying the filter algorithm to images thereafter acquired with the imaging device to create a filtered image that has a spatial resolution that substantially matches the reference spatial resolution.

2. The method of claim 1 wherein the measured spatial resolution of the image of the phantom and reference spatial resolution are a full width half maximum.

3. The method of claim 1 wherein the filtered image is used to compute a coronary calcium score.

4. The method of claim 3 where the coronary calcium score is an Agatston Score.

5. The method of claim 3 where the coronary calcium score is a volume score.

6. The method of claim 3 where the coronary calcium score is an integral score.

7. The method of claim 3 wherein the calcium scores from the filtered images are input into a database for comparison with scores from other images that comprise the reference spatial resolution.

8. The method of claim 1 wherein measuring is carried out periodically.

9. The method of claim 8 wherein periodically comprises once a day.

10. The method of claim 1 wherein the phantom comprises a plurality of aluminum wires comprising different dimensions embedded in a low density matrix.

11. The method of claim 10 wherein the aluminum wires comprise a diameter that is between approximately 0.1 times the full width half maximum of the imaging device and 3.0 times the full width half maximum of the imaging device.

12. The method of claim 10 wherein measuring the spatial resolution of the phantom comprises measuring a peak signal for each wire.

13. The method of claim 1 wherein comparing is carried out with software.

14. The method of claim 1 wherein the imaging device is a CT scanner and the signal is an absorption signal.

15. The method of claim 14 wherein applying the filter algorithm comprises filtering data from detectors of the CT scanner before a reconstruction yields the image.

16. The method of claim 15 wherein applying the filter algorithm comprises multiplying a signal distribution of the images along the detectors by a set of weights that yield the reference spatial resolution.

17. The method of claim 15 where the reconstruction is a back projection.

18. The method of claim 1 wherein the filter algorithm performs at least one of smoothing and sharpening of the acquired images.

19. The method of claim 1 wherein applying the filter algorithm comprises convolving the image with one of a Gaussian filter, Fourier filter, or a cubic filter so that the spatial resolution of the images are adjusted to the reference spatial resolution.

20. The method of claim 1 wherein applying the filter algorithm comprises:

applying an inverse Fourier Transform to the acquired image;

filtering a frequency space two-dimensional data of the acquired image; and

performing a forward Fourier Transform to obtain an image comprising the reference spatial resolution.

21. The method of claim 1 wherein applying the filter algorithm comprises:

applying an inverse Fourier Transform to a single line of the acquired image;

filtering a frequency space one-dimensional data of the acquired image; and

performing a forward Fourier Transform to obtain an image comprising the reference spatial resolution;

repeating the applying, filtering and performing steps on all lines that are parallel and perpendicular to the single line.

22. The method of claim 1 wherein applying the filter algorithm comprises filtering absorption data.

23. The method of claim 22 wherein filtering of the absorption data comprises filtering prior to reconstruction.

24. The method of claim 23 wherein reconstruction is a back projection.

25. The method of claim 1 wherein applying the filtering algorithm comprises applying a two-dimensional operator to the image.

26. The method of claim 1 wherein filtering comprises applying a one-dimensional operator to a line of the image;

repeating the applying step to all lines that are parallel to the line; and

repeating the applying step to all lines that are perpendicular to the line.

27. A method of filtering images, the method comprising:

providing an algorithm;

obtaining at least one image with an imaging device; and

applying the algorithm to the obtained image(s) to adjust a spatial resolution of the obtained image(s) to create resolution-adjusted image(s) that have a spatial resolution that substantially matches a reference spatial resolution.

28. A system for improving coronary and other vessel calcium scoring consistency, the system comprising:

an imaging unit that measures a spatial resolution of an image of a phantom; and

a computer system coupled to the imaging unit, the computer system comprising;

a memory that stores a reference spatial resolution;

means for comparing the measured spatial resolution of the image of the phantom with the reference spatial resolution stored in the memory; and

means for creating resolution-adjusted images in which the spatial resolution of the resolution-adjusted images are adjusted to match the reference spatial resolution.

29. The system of claim 28 wherein the phantom comprises a plurality of objects having known characteristics.

30. The system of claim 29 wherein the plurality of objects comprises aluminum wires having varied diameters which are between 0.1 and 3.0 times the spatial resolution of the imaging unit.

31. The system of claim 28 wherein the imaging unit is a CT scanner.

32. The system of claim 28 wherein the resolution adjusted image(s) are used to compute a coronary calcium score.

33. The system of claim 32 wherein the coronary calcium score is an Agatston Score.

34. The system of claim 32 wherein the coronary calcium score is a volume score.

35. The method of claim 32 where the coronary calcium score is an integral score.

36. A database for storing coronary calcium information, the database comprising a plurality of calcium scored from filtered images comprising a spatial resolution that has been filtered to substantially match a reference spatial resolution.

37. A phantom for calibrating a spatial resolution of a imaging device, the phantom comprising:

a housing; and

a plurality of substantially cylindrical bodies positioned in a spaced configuration within the housing.

38. The phantom of claim 37 wherein the cylindrical bodies have a diameter that is between approximately 0.1 times the full width half maximum and 3.0 times the full width half maximum of the imaging device.

39. The phantom of claim 37 wherein the full-width half maximum of the imaging devices is between 0.9 mm FWHM and 1.7 mm FWHM.

40. The phantom of claim 37 wherein the housing comprises first and second parallel surfaces, and wherein a longitudinal axis of the cylindrical bodies is substantially perpendicular to the first and second surfaces.

41. The phantom of claim 37 wherein the cylindrical bodies comprise aluminum wires.

42. The phantom of claim 37 wherein the cylindrical bodies are embedded in a fluid or solid with electron density similar to that of water in the housing.

43. The phantom of claim 37 wherein the plurality of elongate bodies comprise five aluminum or hydroxy apatite wires.

44. A method of improving the consistency of coronary calcium scoring, the method comprising:

comparing the spatial resolution of the imaging scanner against a reference spatial resolution;

choosing a filter algorithm that will alter the spatial resolution of the image of the phantom to substantially match the reference spatial resolution; and

applying the filter algorithm to images thereafter acquired with the imaging device to create a filtered image that has a spatial resolution that substantially matches the reference spatial resolution.

45. The method of claim 44 wherein the measured spatial resolution of the image of the phantom and reference spatial resolution are a full width half maximum.

46. The method of claim 44 wherein the filtered image is used to compute a coronary calcium score.

47. The method of claim 46 where the coronary calcium score is an Agatston Score.

48. The method of claim 46 where the coronary calcium score is a volume score.

49. The method of claim 46 where the coronary calcium score is an integral score.

50. The method of claim 46 wherein the calcium scores from the filtered images are input into a database for comparison with scores from other images that comprise the reference spatial resolution.

51. The method of claim 44 wherein measuring is carried out periodically.

52. The method of claim 51 wherein periodically comprises once a day.

53. The method of claim 44 wherein the phantom comprises a plurality of aluminum wires comprising different dimensions embedded in a low density matrix.

54. The method of claim 53 wherein the aluminum wires comprise a diameter that is between approximately 0.1 times the full width half maximum of the imaging device and 3.0 times the full width half maximum of the imaging device.

55. The method of claim 53 wherein measuring the spatial resolution of the phantom comprises measuring a peak absorption signal for each wire.

56. The method of claim 44 wherein comparing is carried out with software.

57. The method of claim 44 wherein the imaging device is a CT scanner.

58. The method of claim 57 wherein applying the filter algorithm comprises filtering data from detectors of the CT scanner before a reconstruction yields the image.

59. The method of claim 58 wherein applying the filter algorithm comprises multiplying a signal distribution of the images along the detectors by a set of weights that yield the reference spatial resolution.

60. The method of claim 58 where the reconstruction is a back projection.

61. The method of claim 44 wherein the filter algorithm performs at least one of smoothing and sharpening of the acquired images.

62. The method of claim 44 wherein applying the filter algorithm comprises convolving the image with one of a Gaussian filter, Fourier filter, or a cubic filter so that the spatial resolution of the images are adjusted to the reference spatial resolution.

63. The method of claim 44 wherein applying the filter algorithm comprises:

applying an inverse Fourier Transform to the acquired image;

filtering a frequency space two-dimensional data of the acquired image; and

performing a forward Fourier Transform to obtain an image comprising the reference spatial resolution.

64. The method of claim 44 wherein applying the filter algorithm comprises:

applying an inverse Fourier Transform to a single line of the acquired image;

filtering a frequency space one-dimensional data of the acquired image; and

performing a forward Fourier Transform to obtain an image comprising the reference spatial resolution;

repeating the applying, filtering and performing steps on all lines that are parallel and perpendicular to the single line.

65. The method of claim 44 wherein applying the filter algorithm comprises filtering absorption data.

66. The method of claim 65 wherein filtering of the absorption data comprises filtering prior to reconstruction.

67. The method of claim 66 wherein reconstruction is a back projection.

68. The method of claim 44 wherein applying the filtering algorithm comprises applying a two-dimensional operator to the image.

69. The method of claim 44 wherein filtering comprises applying a one-dimensional operator to a line of the image;

repeating the applying step to all lines that are parallel to the line; and

repeating the applying step to all lines that are perpendicular to the line.

70. A method of improving a comparison of calcium scores, the method comprising:

providing an algorithm;

obtaining at least one image with an imaging device;

applying the algorithm to the obtained image(s) to adjust a spatial resolution of the obtained image(s) to create resolution-adjusted image(s) that have a spatial resolution that substantially matches a reference spatial resolution; and

scoring the corrected image.

71. The method of claim 70 wherein providing comprises periodically measuring the spatial resolution of the imaging device and adjusting the algorithm based on the measuring of the spatial resolution of the imaging device.

72. The method of claim 71 wherein periodically monitoring occurs once a day.

73. The method of claim 71 wherein periodically monitoring comprises:

imaging a phantom;

comparing the spatial resolution of the imaged phantom to a reference spatial resolution; and

generating the algorithm that adjusts the spatial resolution of the imaged phantom to substantially match the reference spatial resolution.

74. The method of claim 73 wherein the phantom comprises a plurality of wires that have a diameter that is between approximately 0.1 times as large as a full width half maximum of the imaging device and 3.0 times as large as the full width half maximum of the imaging device.

75. The method of claim 70 wherein applying the algorithm comprises at least one of smoothing and sharpening the obtained image.

76. The method of claim 70 wherein the resolution corrected image is used to compute a coronary calcium score.

77. The method of claim 76 wherein the coronary calcium score is an Agatston Score.

78. The method of claim 76 wherein the coronary calcium score is a volume score.

79. The method of claim 76 where the coronary calcium score is an integral score.