Multi-mode tomosynthesis/mammography gain calibration and image correction using gain map information from selected projection angles

1. A breast tomosynthesis method comprising:

acquiring tomosynthesis projection x-ray images T(p,n) of a phantom, where the index p designates a respective one of a first multiplicity of P first projection angles of an x-ray beam relative to the phantom, p=1, 2, 3, . . . , P, the index n designates the number of projection images taken at a given one of the first projection angles, and n≧2;

generating enhanced gain maps EG(p′), where the index p′ designates a respective one of a second multiplicity of P′ second projection angles of an x-ray beam relative to a patient's breast and p′=1, 2, 3, . . . , P′, in a computer-implemented process combining parameters derived from said images T(p,n);

acquiring tomosynthesis x-ray images T′(p′) of a patient's breast at said second projection angles;

gain-correcting the tomosynthesis x-ray images T′(p′) of the patient's breast using the enhanced gain maps EG(p′) in a computer-implemented process to thereby produce gain-corrected breast images; and

further computer-processing said gain-corrected breast images and displaying breast images resulting from said further computer-processing.

2. A breast tomosynthesis method as in claim 1 in which said parameters derived from the phantom images T(p,n) comprise respective initial gain maps G(p) for said first projection angles.

3. A breast tomosynthesis method as in claim 2 in which said combining comprises combining initial gain maps G(p) for P>M≧2 first projection angles to generate an enhanced gain map EG(p′) for a given second projection angle.

4. A breast tomosynthesis method as in claim 3 in which M=2D+1 and D≧1.

5. A breast tomosynthesis method as in claim 4 in which D=1.

6. A breast tomosynthesis method as in claim 4 in which the value of D is selectable and changeable.

7. A breast tomosynthesis method as in claim 6 in which the value of D is selectable and changeable by a user of a tomosynthesis system carrying out said tomosynthesis method.

8. A breast tomosynthesis method as in claim 3 in which said combining comprises averaging of said initial gain maps G(p) for different ones of said first projection angles.

9. A breast tomosynthesis method as in claim 3 in which said combining comprises applying different weighting factors to different ones of said initial gain maps G(p) for different ones of said first projection angles.

10. A breast tomosynthesis method as in claim 9 in which said combining in order to generate an enhanced gain map EG(p′) for a given one of said second projection angles comprises applying greater weight to an initial gain map G(p) for a first projection angle that is closer to said given one of the second projection angles than to an initial gain map G(p) for a first projection angle that is further from said given one of the second projection angles.

11. A breast tomosynthesis method as in claim 3 in which the enhanced gain map EG(p′) for a given one of said second projection angle is generated by combining the initial gain maps G(p) for the M second projection angles that are nearest to the given second projection angle.

12. A breast tomosynthesis method as in claim 3 in which each of a subset of the enhanced gain maps EG(p′) is for a second projection angle that does not coincide with a first projection angle and said combining to generate each enhanced gain map EG(p′) of said subset comprises interpolation between values included in initial gain maps G(p) for M first projection angles.

13. A breast tomosynthesis method as in claim 2 in which said combining comprises combining initial gain maps G(p) for M=P first projection angles to generate each of said enhanced gain maps EG(p′).

14. A breast tomosynthesis method as in claim 13 in which said combining comprises applying different weight factors to the initial gain maps G(p) used to generate the respective enhanced gain maps EG(p′) for different ones of said second projection angles.

15. A breast tomosynthesis method as in claim 14 in which said different weighting factors are related to differences between said first projection angles and said second projection angles.

16. A breast tomosynthesis method as in claim 1 in which the generating of an enhanced gain maps EG(p′) for a given one of the second projection angles comprises combining parameters derived from phantom projection images T(p,n) acquired at a single one of said first projection angles.

17. A breast tomosynthesis method as in claim 1 in which said combining comprises combining parameters derived from phantom images T(p,n) for P>M≧2 first projection angles to generate an enhanced gain map EG(p′) for a given second projection angle.

18. A breast tomosynthesis method as in claim 17 in which M=2D+1 and D≧1.

19. A breast tomosynthesis method as in claim 18 in which D=1.

20. A breast tomosynthesis method as in claim 18 in which the value of D is selectable and changeable.

21. A breast tomosynthesis method as in claim 18 in which the value of D is selectable and changeable by a user of a tomosynthesis system carrying out said tomosynthesis method.

22. A breast tomosynthesis method as in claim 17 in which said combining comprises averaging of said parameters derived from phantom images T(p,n) acquired at different ones of said first projection angles.

23. A breast tomosynthesis method as in claim 17 in which said combining comprises applying different weighting factors to different ones of said parameters derived from phantom images T(p,n) acquired at different ones of said first projection angles.

24. A breast tomosynthesis method as in claim 23 in which said combining in order to generate an enhanced gain map EG(p′) for a given one of said second projection angles comprises applying greater weight to the parameters derived from the phantom images T(p,n) acquired at the first projection angle that is closer to said given one of the second projection angles than to parameters derived from phantom images T(p,n) acquired at a first projection angle that is further from said given one of the second projection angles.

25. A breast tomosynthesis method as in claim 17 in which the enhanced gain map EG(p′) for a given one of said second projection angle is generated by combining parameters derived from the phantom images T(p,n) acquired at the M first projection angles that are nearest to the given second projection angle.

26. A breast tomosynthesis method as in claim 17 in which each of a subset of the enhanced gain maps EG(p′) is for a second projection angle that does not coincide with a first projection angle and said combining to generate each enhanced gain map EG(p′) of said subset comprises interpolation between values included in or derived from the phantom images T(p,n) acquired at the M first projection angles.

27. A breast tomosynthesis method as in claim 17 in which more than two phantom projection images are acquired at each of the first projection angles.

28. A breast tomosynthesis method as in claim 17 in which six phantom projection images are acquired at each of the first projection angles.

29. A breast tomosynthesis method as in claim 17 in which said combining comprises combining parameters derived from phantom projection images T(p,n) acquired at M=P first projection angles to generate each of said enhanced gain maps EG(p′).

30. A breast tomosynthesis method as in claim 29 in which said combining comprises applying different weighting factors to the parameters derived from phantom images T(p,n) acquired at different ones of said M first projection angles to generate the respective enhanced gain maps EG(p′) for different ones of said second projection angles.

31. A breast tomosynthesis method as in claim 30 in which said different weighting factors are related to differences between said first projection angles and said second projection angles.

32. A breast tomosynthesis method comprising:

acquiring tomosynthesis projection x-ray images of a phantom at each of a multiplicity of first projection angles of an x-ray beam relative to the phantom;

generating respective first gain maps for said first projection angles wherein said first gain maps are related to differences between expected and actual characteristics of pixel values in said projection x-ray images of the phantom;

acquiring tomosynthesis x-ray images of a patient's breast for each of a multiplicity of second projection angles, wherein the second projection angles differ in number or in angle values from said first projection angles;

deriving respective enhanced gain maps for said second projection angles by computer-processing parameters derived from said first gain maps;

gain-correcting said tomosynthesis x-ray images of the patient's breast using said enhanced gain maps; and

further computer-processing said gain-corrected breast images and displaying breast images resulting from said further computer-processing.

33. A breast tomosynthesis method as in claim 32 in which said deriving comprises an interpolation process.

34. A breast tomosynthesis method as in claim 32 in which said second projection angles are greater in number than said first projection angles.

35. A breast tomosynthesis method as in claim 32 in which said enhanced gain maps are greater in number than said first gain maps.

36. A breast tomosynthesis method as in claim 32 in which said deriving of an enhanced gain map for a given second projection angle comprises using parameters of at least one first gain map for a projection angle that is closest in angle value to the given second projection angle.

37. A breast tomosynthesis method as in claim 32 in which said acquiring of tomosynthesis x-ray images of the patient's breast comprises selecting the number of said second projection angles by a user of a tomosynthesis system carrying out the method.

38. A breast tomosynthesis method as in claim 32 in which said acquiring of tomosynthesis x-ray images of the patient's breast comprises selecting the angle values of said second projection angles by a user of a tomosynthesis system carrying out the method.

39. A method of operating a multi-mode tomosynthesis/mammography system comprising:

operating the system in a mammography mode and acquiring a mammographic image of a phantom using x-ray parameters for mammography and generating a mammography gain map from said mammographic image;

operating the system in a tomosynthesis mode and acquiring tomosynthesis projection x-ray images of the same or different phantom, where at least one phantom projection image is acquired for each of a multiplicity of different first projection angles relative to the phantom;

generating initial tomosynthesis gain maps for said first projection angles using said tomosynthesis projection images of the phantom;

forming at least one enhanced tomosynthesis gain map by combining at least some of the initial tomosynthesis gain maps;

selectively operating the system in one of the mammography mode to acquire x-ray mammogram images of a patient's breast and the tomosynthesis mode to acquire tomosynthesis x-ray images of a patient's breast at a multiplicity of second projection angles;

automatically selecting the mammography gain map and gain-correcting the mammogram images therewith when acquiring breast images in the mammography mode and selecting the at least one enhanced tomosynthesis gain map and gain-correcting therewith the tomosynthesis breast images when operating in the tomosynthesis mode; and

selectively displaying the resulting gain-corrected mammogram images and/or tomosynthesis images.

40. A method of operating a multi-mode tomosynthesis/mammography system as in claim 39 in which said gain-correcting of the tomosynthesis breast images comprises using the same enhanced gain map for a plurality of said tomosynthesis breast images.

41. A method of operating a multi-mode tomosynthesis/mammography system as in claim 40 in which said gain-correcting of the tomosynthesis breast images comprises using the same enhanced gain map for each of said tomosynthesis breast images.

42. A method of operating a multi-mode tomosynthesis/mammography system as in claim 39 in which said gain-correcting of the tomosynthesis breast images comprises using different enhanced gain maps for different ones of said tomosynthesis breast images.

43. A method of operating a multi-mode tomosynthesis/mammography system as in claim 39 in which said operating the system in said tomosynthesis mode comprises user selection of the number and/or angle values of said second projection angles for acquisition of said tomosynthesis projection images of the breast.

44. A breast tomosynthesis system comprising:

an image acquisition unit comprising an x-ray source and an x-ray image receptor, said unit acquiring projection x-ray images of an object at selected projection angles;

an initial gain map generator configured to receive x-ray projection images taken with said image acquisition unit of a phantom at a multiplicity of first projection angles, said initial gain map generator being further configured to process the projection images of the phantom received thereby and generate therefrom an initial gain map for each of said first projection angles;

an enhanced gain map generator configured to receive said initial gain maps, said enhanced map generator being further configured to process the initial gain maps received thereby and generate therefrom at least one enhanced gain map; and

an image generator configured to receive said enhanced gain maps and tomosynthesis x-ray images of a patient's breast taken with said image acquisition unit at a multiplicity of second projection angles, said image generator being further configured to gain-correct said breast images with said at least one enhanced gain map.

45. A breast tomosynthesis system as in claim 44 in which said enhanced map generator is configured to generate a single enhanced gain map and said image generator is configured to correct at least a subset of several of said breast images with said single enhanced gain map.

46. A breast tomosynthesis system as in claim 44 in which said enhanced map generator is configured to generate a multiplicity of different enhanced gain maps and said image generator is configured to correct each of at least a subset of several of said breast images with a different one of said enhanced gain maps.

47. A breast tomosynthesis system as in claim 44 in which said enhanced map generator is configured to generate a respective enhanced gain map for each of said second projection angles and said image generator is configured to correct each of said breast images with a respective one of said enhanced gain maps.

48. A breast tomosynthesis system as in claim 44 in which said first projection angles and said second projection angles differ from each other, and said enhanced map generator is configured to account for said difference between the first and second projection angles in generating said at least one enhanced gain map.

49. A breast tomosynthesis system as in claim 44 in which said first projection angles and said second projection angles differ from each other, and said enhanced map generator is configured to generate respective enhanced gain maps for said second projection angles by interpolation from parameters of said initial gain maps.

50. A breast tomosynthesis system as in claim 49 in which said first projection angles and said second projection angles differ from each other, and said enhanced map generator is configured to generate respective preliminary enhanced gain maps for said first projection angles and process said preliminary enhanced gain maps to generate therefrom respective final enhanced maps to the second projection angles, and said image generator is configured to gain-correct said breast images with said final enhanced gain maps.