Scatter rejection for composite medical imaging systems

• US 20040202360A1
• Filed: 04/11/2003
• Published: 10/14/2004
• Est. Priority Date: 04/11/2003
• Status: Active Grant

• Current Assignee: Hologic Incorporated
• Original Assignee: Hologic Incorporated
• Inventors: Besson, Guy M.
• Granted Patent: US 7,352,887 B2
• Time in Patent Office: Days
• US Class Current: 382/131
• CPC Class Codes: A61B 6/5282 due to scatter
• CPC Class Codes: G06T 2207/10116 X-ray image
• CPC Class Codes: G06T 2207/30068 Mammography; Breast
• CPC Class Codes: G06T 5/94 based on local image properties, e.g. for local contrast enhancement

Abstract

Scatter effects are reduced in a radiographic imaging device, such as a digital slot scan mammographic imaging device, by reducing detected scatter and processing detector information to compensate for scatter effects. In one embodiment, a digital mammographic imaging system (10) includes a source (24) for transmitting a narrow beam (28) and a detector assembly (32) for detecting the beam (28). The beam (28) and the detector assembly (32) are synchronously scanned across the patient'"'"'s breast (48) to obtain an image. Collimator slats (74) are provided at the leading and trailing edges of the detector to reduce detected scatter. Additionally, attenuators (76 and 92) are provided at the ends of the scanned motion and at the anterior edge of the detector array to assist in determining a spatial intensity profile. The spatial intensity profile information together with other imaging signal and patient dependent parameters are used in image processing to estimate and compensate for various scatter effects including single and multiple scatters and Compton and Rayleigh scatter.

Claims

1. A method of imaging a selected tissue region of a patient'"'"'s body, comprising the steps of:

transmitting radiation into said selected tissue region of said patient'"'"'s body during an exposure period;

detecting radiation from said selected tissue region of said patient'"'"'s body, wherein detected radiation from said selected tissue region includes a scattered portion corresponding with photonic energy scattered within said selected tissue region, and a non-scattered portion corresponding with photonic energy passing through said selected tissue region substantially free from scattering;

estimating first and second parts of said scattered portion, wherein said first part corresponds with photonic energy passing through said selected tissue region with a single scattering occurrence, and wherein said second part corresponds with photonic energy passing through said selected tissue region with multiple scattering occurrences;

obtaining radiographic image data in relation to said detected radiation from said selected tissue region; and

,

utilizing the estimated first and second parts of said scattered portion to adjust said radiographic image data.

2. A method as recited in claim 1, wherein said first part includes at least one of a Compton scatter component and a Rayleigh scatter component.

3. A method as recited in claim 2, wherein said estimating step includes:

determining said at least one of a Compton scatter component and a Rayleigh scatter component as a function of a measured dimension of said selected tissue region.

4. A method as recited in claim 3, wherein said estimating step further includes:

determining each of a Compton scatter component and a Rayleigh scatter component as a function of said measured dimension of said selected tissue region.

5. A method as recited in claim 3, wherein said estimating step further includes:

determining said second part of said scattered portion as a function of said measured dimension of said selected tissue region.

6. A method as recited in claim 3, further comprising:

locating said selected tissue region at a substantially fixed location;

measuring a thickness of said selected tissue region, wherein said thickness is employed as said measured dimension in said determining step; and

,

completing said transmitting, measuring and obtaining steps during said locating step.

7. A method as recited in claim 6, wherein said locating step includes:

compressing said selected tissue region with a known compression force; and

, wherein said estimating step further includes;

determining said at least one of a Compton scatter component and a Rayleigh scatter component as a function of said thickness of and said compression force applied to said selected tissue region.

8. A method as recited in claim 3, wherein said estimating step further includes:

determining said at least one of a Compton scatter component and a Rayleigh scatter component as a function of said measured dimension and an estimated density of at least a portion of said selected tissue region.

9. A method as recited in claim 8, wherein said estimating step further includes:

determining each of a Compton scatter component and a Rayleigh scatter component as a function of said measured dimension and said estimated density of said selected tissue region.

10. A method as recited in claim 8, further comprising:

selecting said estimated density from a plurality of estimated densities that correspond with a plurality of predetermined tissue types.

11. A method as recited in claim 8, wherein said estimating step further includes:

determining said at least one of a Compton scatter component and a Rayleigh scatter component as a function of said measured dimension, said estimated density and an estimated intensity value of said transmitted radiation incident upon said selected tissue region.

12. A method as recited in claim 11, further comprising:

setting a power level for said radiation transmission; and

,

establishing said estimated intensity value as a function of said power level.

13. A method as recited in claim 12, further comprising:

locating said selected tissue region at a substantially fixed location;

measuring an intensity value of said transmitted radiation;

completing said transmitting, obtaining and measuring steps during said locating step; and

,

adjusting said estimated intensity value utilizing said measured intensity value, wherein an adjusted intensity value is obtained for use in said estimating step.

14. A method as recited in claim 1, wherein said estimating step includes:

determining at least one of a Compton scatter component and a Rayleigh scatter component as a function of an intensity value of said transmitted radiation incident upon said selected tissue region.

15. A method as recited in claim 14, wherein said intensity value is an estimated intensity value, and further comprising:

setting a power level for said radiation transmissions; and

,

establishing said estimated intensity value as a function of said power level.

16. A method as recited in claim 15, further comprising:

locating said selected tissue region at a substantially fixed location;

measuring an intensity of said detected radiation;

completing said transmitting, obtaining and measuring steps during said locating step; and

,

adjusting said estimated intensity value utilizing said measured intensity, wherein an adjusted intensity value is used in said determining step.

17. A method as recited in claim 16, wherein said substantially fixed location corresponds to a predetermined imaging frame of reference, wherein said predetermined imaging frame of reference comprises a plurality of areas, and wherein said obtaining, estimating and utilizing steps are completed in separate, corresponding relation to each of said plurality of areas.

18. A method as recited in claim 17, wherein said plurality of areas define a matrix having at least a first dimension, and wherein said establishing and measuring steps are completed in separate, corresponding relation to each of said plurality of areas as a function of location in said at least first dimension.

19. A method as recited in claim 17, wherein said matrix has a second dimension, and wherein said establishing and measuring steps are completed in separate corresponding relation to each of said plurality of areas as a function of location in each of said first and second dimensions.

20. A method as recited in claim 19, wherein said measuring step includes:

detecting a plurality of intensities of said transmitted radiation utilizing first and second arrays of pixel elements extending in said first and second dimensions, respectively, and located outside of said predetermined imaging frame of reference.

21. A method as recited in claim 17, wherein said plurality of areas define a matrix having first and second dimensions, and wherein said obtaining step includes:

detecting said transmitted radiation passing through said selected tissue region utilizing an active array of pixel elements extending entirely across said predetermined imaging frame of reference in said second dimension and partially across said predetermined imaging frame of reference in said first dimension.

22. A method as recited in claim 21, wherein said detecting step includes:

moving said active array of pixel elements across said predetermined imaging frame of reference.

23. A method as recited in claim 22, wherein said transmitting step includes:

scanning a radiation beam across said predetermined frame of reference synchronous with said movement of the array.

24. A method as recited in claim 22, further comprising:

optically blocking some of said second part of said scattered portion from reaching said array of pixel elements.

25. A method as recited in claim 1, wherein said utilizing step includes:

subtracting said first and second parts from said radiographic image data to adjust the image data; and

,

displaying the adjusted radiographic image data.

26. A method as recited in claim 1, further comprising obtaining a first value related to a first tissue composition corresponding to a first portion of said selected tissue region and a second value related to a second tissue composition corresponding to a second portion of said selected tissue region and using said first and second values to estimate one of said first and second parts of said scattered portion.

27. An apparatus for use in imaging a selected tissue region of a patient'"'"'s body, comprising:

a source for transmitting radiation into said selected region of said patient'"'"'s body;

a detector for detecting radiation from said selected region of said patient'"'"'s body, wherein detected radiation from said selected tissue region includes a scattered portion corresponding with photonic energy scattered within said selected tissue region, and a non-scattered portion corresponding with photonic energy passing through said selected tissue region substantially free from scattering; and

a processor operative for;

estimating first and second parts of said scattered portion, wherein said first part corresponds with photonic energy passing through said selected tissue region with a single scattering occurrence, and wherein said second part corresponds with photonic energy passing through said selected tissue region with multiple scattering occurrences;

obtaining radiographic image data in relation to said detected radiation from said selected tissue region; and

,

utilizing the estimated first and second parts of said scattered portion to adjust said radiographic image data.

28. An application as set forth in claim 27, wherein said source is operative for transmitting said radiation in a form of a beam having a first beam dimension that is less than a corresponding dimension of said selected region of said patient'"'"'s body.

29. An application as set forth in claim 28, wherein said source is operative for scanning said beam across said area of interest.

30. An application as set forth in claim 27, wherein said detector includes and active detector area having a first detector dimension less than a corresponding dimension of said patient'"'"'s body.

31. An application as set forth in claim 27, wherein said processor is operative for receiving scatter related parameter information for a specific imaging procedure and using said parameter information to estimate one of said first and second parts.

32. An application as set forth in claim 31, wherein said processor is operative for using said parameter information to estimate both of said first and second parts.

33. An application as set forth in claim 31, wherein said parameter information relates to an intensity of radiation transmitted by said source.

34. An application as set forth in claim 31, wherein said parameter information relates to a density of at least a portion of said selected tissue region of said patient'"'"'s body.

35. An application as set forth in claim 27, wherein said processor is operative for receiving measurement information, obtained with said patient disposed in an imaging position relative to said source and said detector, and using said measurement information to estimate one of said first and second parts.

36. An application as set forth in claim 35, wherein said processor is operative for using said measurement information to estimate both of said first and second parts.

37. An application as set forth in claim 35, wherein said measurement information relates to a dimension of said selected tissue region of said patient'"'"'s body.

38. An application as set forth in claim 35, wherein said measurement information relates to a compression force exerted on said selected tissue region of said patient'"'"'s body.

39. An application as set forth in claim 35, wherein said measurement information relates to an intensity of radiation incident on a detector area outside of a predetermined imaging frame of reference corresponding to said selected tissue region.

40. An application as set forth in claim 34, wherein said measurement information relates to intensities of radiation incident on multiple detector areas outside of a tissue imaging portion of said detector.

41. An application as set forth in claim 35, wherein said measurement information relates to a profile, relative to a first axis of said detector, of radiation intensities incident on said detector.

42. An application as set forth in claim 41, wherein said measurement information relates to a profile, relative to a second axis different than said first axis, of radiation intensities incident on said detector.

43. An application as set forth in claim 35, wherein said measurement information relates to a spacing between said selected tissue region and said detector.

44. An application as set forth in claim 35, further comprising a user interface for entering said measurement information.

45. An application as set forth in claim 35, further comprising a measurement device for use in automatically obtaining said measurement information.

46. An application as set forth in claim 45, wherein said measurement device provides information regarding a dimension of said selected region of said patient'"'"'s body.

47. An application as set forth in claim 45, wherein said measurement device provides information regarding a compression force applied to said selected region of said patient'"'"'s body.

48. An application as set forth in claim 45, wherein said measurement device comprises a portion of said detector.

49. An application as set forth in claim 27, further comprising an attenuator having known radiation attenuation characteristics for attenuating, on a spatially dependent basis, radiation directed to said detector wherein said attenuator is positioned relative to said detector outside of a predetermined frame of reference corresponding to said selected tissue region.

50. An application as set forth in claim 27, wherein said processor is operative for determining a spacing between said selected tissue region and said detector so as to reduce one of said first and second parts of said scatter portion.

51. An application as set forth in claim 50, further comprising a positioning mechanism for use in establishing said spacing between said selected tissue region and said detector.

52. An application as set forth in claim 51, wherein said positioning mechanism is operative for establishing said spacing free from movement of said selected tissue region.

53. An application as set forth in claim 27, further comprising a measurement device for measuring scattered radiation during said transmitting step.

54. An application as set forth in claim 53, wherein said source transmits a beam of radiation and said measurement device comprises a portion of said detector outside of an area of a predetermined frame of reference corresponding to said selected tissue region.

55. A method of imaging a selected tissue region of a patient'"'"'s body, comprising the steps of:

transmitting radiation into said selected tissue region of said patient'"'"'s body during an exposure period;

detecting radiation from said selected tissue region of said patient'"'"'s body, wherein detected radiation from said selected tissue region includes a scattered portion corresponding with photonic energy scattered within said selected tissue region, and a non-scattered portion corresponding with photonic energy passing through said selected tissue region substantially free from scattering;

positioning a patient in a desired position for a radiographic procedure;

with said patient positioned in said desired position, operating a parameter measurement device to measure a procedure specific value of a scatter related parameter and provide an output indicative thereof;

obtaining radiographic image data in relation to said detected radiation from said selected tissue region; and

operating a processor to receive said output and use said image-specific value of said scatter related parameter to adjust said radiographic image data.

56. A method as set forth in claim 55, wherein said step of operating a processor comprises estimating first and second parts of said scatter portion, wherein said first part corresponds with photonic energy passing through said selected tissue region with a single scattering occurrence, and wherein said second part corresponds with photonic energy passing through said selected tissue region with multiple scattering occurrences.

57. A method as set forth in claim 56, wherein said first part includes at least one of a Compton scatter component and a Rayleigh scatter component.

58. A method as set forth in claim 55, wherein said step of operating said processor comprises determining at least one of a Compton scatter component and a Rayleigh scatter component as a function of a measured dimension of said selected tissue region.

59. A method as set forth in claim 55, wherein said step of operating said processor comprises determining at least one of a Compton scatter component and a Rayleigh scatter component as a function of an estimated density of at least a portion of said selected tissue region.

60. A method as set forth in claim 55, wherein said step of operating said processor comprises determining one of a Compton scatter component and a Rayleigh scatter component as a function of a transmitted intensity of radiation incident on said selected tissue region.

61. A method as set forth in claim 55, wherein said. step of operating said processor comprises determining one of a Compton scatter component and a Rayleigh scatter component based on a measured intensity of said detected radiation.

62. A method as set forth in claim 55, wherein said step of operating said processor comprises determining one of a Compton scatter component and a Rayleigh scatter component as a function of a spacing between a detector surface and said selected tissue region.

63. A method as set forth in claim 55, wherein said step of obtaining radiographic image data comprises operating a detector to detect said detected radiation and provide a detector output indicative thereof, wherein said detector output reflects imaging information for different portions of interest obtained at corresponding different times of said exposure period.

64. An apparatus for use in imaging a selected tissue region of a patient'"'"'s body, comprising:

a source for transmitting radiation into said selected region of said patient'"'"'s body;

a detector for detecting radiation from said selected region of said patient'"'"'s body and providing first imaging information based thereon;

a patient support for supporting the patient such that said selected region is maintained in a desired imaging position for a radiographic procedure;

a sensor for measuring a procedure specific value of a scatter related parameter with said patient positioned in said desired imaging position and providing a sensor output indicative thereof; and

a processor for receiving said first imaging information and. said sensor output, and providing second imaging information based thereon.

65. An apparatus as set forth in claim 64, wherein said source is operative for transmitting said radiation in a form of a beam having a first beam dimension that is less than a corresponding dimension of said selected region of said patient'"'"'s body.

66. An apparatus as set forth in claim 64, wherein said detector includes an active detective area having a first detector dimension less than a corresponding dimension of said patient'"'"'s body.

67. An apparatus as set forth in claim 64, wherein said selected region of said patient'"'"'s body comprises at least a portion of a patient'"'"'s breast and said patient support comprises a support for supporting said patient'"'"'s breast.

68. An apparatus as set forth in claim 67, wherein said support plate is separated from said detector by a selected air gap distance.

69. An apparatus as set forth in claim 64, wherein said sensor is operative for providing information regarding a dimension of said selected region of said patient'"'"'s body.

70. An apparatus as set forth in claim 64, wherein said sensor is operative for providing information regarding a tissue density of said selected region of said patient'"'"'s body.

71. An apparatus as set forth in claim 64, wherein said sensor is operative for providing information regarding an intensity of radiation incident on said detector.

72. A method for use in imaging a selected tissue region of a patient'"'"'s body, comprising the steps of:

transmitting a photonic energy relative to said area of interest of said patient'"'"'s body during an exposure period of a radiographic procedure;

first operating a detector to detect portions of said photonic energy that have interacted with said area of interest of said patient'"'"'s body and provide a detector output indicative thereof, wherein said detector output reflects imaging information for different portions of said area of interest obtained at corresponding different times of said exposure period;

establishing scatter compensation information for said radiographic procedure; and

second operating a processor to process said detector output, using said scatter compensation information to provide reduced scatter composite imaging information of said area of interest of said patient'"'"'s body.

73. A method as set forth in claim 72, wherein said energy portions include a scattered portion and said step of operating comprises estimating first and second parts of said scattered portion, wherein said first part corresponds with photonic energy passing through said area of interest with a single scattering occurrence, and wherein said second part corresponds with photonic energy passing through said area of interest with multiple scattering occurrences.

74. A method as set forth in claim 73, wherein said first part includes at least one of a Compton scatter component and a Rayleigh scatter-component.

75. A method as set forth in claim 72, wherein said step of second operating comprises determining at least one of a Compton scatter component and a Rayleigh scatter component as a function of a measured dimension of said area of interest.

76. A method as set forth in claim 72, wherein said step of second operating comprises determining at least one of a Compton scatter component and a Rayleigh scatter component as a function of an estimated density of at least a portion of said area of interest.

77. A method as set forth in claim 72, wherein said step of second operating comprises determining one of a Compton scatter component and a Rayleigh scatter component as a function of a transmitted intensity of radiation incident on said area of interest.

78. A method as set forth in claim 72, wherein said step of second operating comprises determining one of a Compton scatter component and a Rayleigh scatter component based on a measured intensity of said detected radiation.

79. A method as set forth in claim 72, wherein said step of second operating comprises determining one of a Compton scatter component and a Rayleigh scatter component as a function of a spacing between a detector surface and said area of interest.

80. An apparatus for use in imaging a selected tissue region of a patient'"'"'s body, comprising:

an imaging source for transmitting photonic energy relative to said area of interest of said patient'"'"'s body during an exposure period of a radiographic procedure;

a detector for detecting portions of said photonic that have interacted with said area of interest of said patient'"'"'s body and providing a detector output indicative thereof, wherein said detector output includes imaging information for different portions of said area of interest obtained at corresponding different times of said exposure period; and

a processor for accessing scatter compensation information for said radiographic procedure and processing said detector output using said scatter compensation information to provide reduced scatter composite imaging information of said area of interest of said patient'"'"'s body.

81. An apparatus as set forth in claim 80, wherein said portions include a scattered portion and said processor is operative for estimating first and second parts of said scatter portion, wherein said first part corresponds with photonic energy passing through said selected tissue region with a single scattering occurrence, and wherein said second part corresponds with photonic energy passing through said selected tissue region with multiple scattering occurrences.

82. An apparatus as set forth in claim 81, wherein said first part includes at least one of a Compton scatter component and a Rayleigh scatter component.

83. An apparatus as set forth in claim 80, wherein said processor is operative for determining at least one of a Compton scatter component and a Rayleigh scatter component as a function of a measured dimension of said area of interest.

84. An apparatus as set forth in claim 80, wherein said processor is operative for determining at least one of a Compton scatter component and a Rayleigh scatter component as a function of an estimated density of at least a portion of said area of interest.

85. An apparatus as set forth in claim 80, wherein said processor is operative for determining one of a Compton scatter component and a Rayleigh scatter component as a function of a transmitted intensity of radiation incident on said area of interest.

86. An apparatus as set forth in claim 80, wherein said processor is operative for determining one of a Compton scatter component and a Rayleigh scatter component based on a measured intensity of said detected radiation.

87. An apparatus as set forth in claim 80, wherein said processor is operative for determining one of a Compton scatter component and a Rayleigh scatter component as a function of a spacing between a detector surface and said area of interest.