Method and apparatus of spectral differential phase-contrast cone-beam CT and hybrid cone-beam CT

• US 10,478,142 B2
• Filed: 04/21/2016
• Issued: 11/19/2019
• Est. Priority Date: 02/11/2013
• Status: Active Grant

• Current Assignee: University of Rochester
• Original Assignee: University of Rochester
• Inventors: Ning, Ruola, Cai, Weixing
• Primary Examiner(s): Midkiff, Anastasia
• Application Number:
  US15/134,581
• Publication Number:
  US 20160374635A1
• Time in Patent Office: 1,307 Days
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4035 the source being combined with a filter or grating
• CPC Class Codes: A61B 6/4085 Cone-beams
• CPC Class Codes: A61B 6/4241 using energy resolving detectors, e.g. photon counting
• CPC Class Codes: A61B 6/4291 the detector being combined with a grid or grating
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: A61B 6/484 involving phase contrast X-ray imaging
• CPC Class Codes: A61B 6/502 for diagnosis of breast, i.e. mammography
• CPC Class Codes: A61B 6/5235 combining images from the same or different ionising radiation imaging techniques, e.g. PET and CT
• CPC Class Codes: G01N 23/087 using polyenergetic X-rays
• CPC Class Codes: G01N 23/20091 Measuring the energy-dispersion spectrum [EDS] of diffracted radiation
• CPC Class Codes: G06T 11/005 Specific pre-processing for tomographic reconstruction, e.g. calibration, source positioning, rebinning, scatter correction, retrospective gating
• CPC Class Codes: G06T 2207/10081 Computed x-ray tomography [CT]
• CPC Class Codes: G06T 2207/20212 Image combination

Abstract

DPC (differential phase contrast) images are acquired for each photon energy channel, which are called spectral DPC images. The final DPC image can be computed by summing up these spectral DPC images or just computed using certain ‘color’ representation algorithms to enhance desired features. In addition, with quasi-monochromatic x-ray source, the required radiation dose is substantially reduced, while the image quality of DPC images remains acceptable.

Claims

1. A method of cone beam CT imaging of a human breast without penetrating the chest cavity of a patient, comprising:

acquiring projection images of the breast taken at different view angles by using a polychromatic x-ray source irradiating the breast but not the chest cavity with primary radiation, an energy-resolving detector having a plurality of energy channels, and a grating system;

said acquiring comprising acquiring, for each of the plurality of energy channels of the detector, a respective plurality of the projection images of the breast taken at different view angles;

performing three-dimensional (3D) computed tomography reconstructions of the breast for each of the plurality of energy channels to produce a respective plurality of differential phase contrast 3D reconstruction images; and

combining the plurality of differential phase 3D reconstruction images to thereby produce one or more output images of the breast;

wherein said combining of the plurality of differential phase 3D reconstruction images comprises assigning different weights to the images being combined.

2. The method of claim 1, wherein said combining of the plurality of differential phase 3D reconstruction images comprises assigning different colors to the images being combined.

3. The method of claim 2, wherein the assigning of different colors comprises applying a two-dimensional matrix of color weighting coefficients to the images being combined.

4. The method of claim 1, wherein the combining produces the output image comprising three-dimensional (3D) matrix of attenuation coefficients of breast tissue voxels.

5. The method of claim 1, wherein the combining produces an output image comprising a three-dimensional (3D) matrix of phase coefficients of breast tissue voxels.

6. The method of claim 1, including stepping a source grating, which is between the x-ray source and the breast, to vary the spacing of the source grating from the x-ray source for different portions of said acquisition.

7. The method of claim 6, wherein the stepping comprises moving the source grating linearly along an imaging x-ray beam from the source irradiating the breast.

8. The method of claim 6, wherein the stepping comprises moving, to a different position between the x-ray source and the breast for different portions of said acquisition, a source grating mounted on a respective branch of a multi-branch source grating mechanism.

9. The method of claim 8, wherein the stepping comprises rotating the multi-branch source grating mechanism about an axis along a propagation direction of the imaging x-ray beam.

10. The method of claim 1 in which the grating system comprises a phase grating and an analyzer grating that are between the breast and the detector, and said acquiring comprises acquiring the projection images while the phase and analyzer grating are misaligned to thereby produce a Moire pattern at the detector.

11. The method of claim 1, further comprising the following steps carried out before said acquiring of the projection images with the polychromatic source:

imaging the breast using a different imaging modality to determine a region of interest in the breast; and

selecting a relative position between an imaging beam from the polychromatic x-ray source and the breast determined by said region of interest and then carrying out the steps recited in claim 1.

12. The method of claim 11 in which the different imaging modality is CT imaging other than differential phase imaging.

13. The method of claim 1, wherein the combining of the 3D reconstruction images comprises producing a combined image resolving sub-micron structures in the breast.

14. A breast CT system imaging a human breast with an x-ray imaging beam without penetrating the chest cavity of a patient with primary radiation, comprising:

a projection image acquisition gantry a polychromatic x-ray source configured to irradiate the breast but not the chest cavity of a patient with an imaging beam of x-rays rotating around the breast, an energy-resolving detector configured to receive the imaging beam after passage thereof through the breast, and a grating system;

said detector being configured to acquire, for each of the plurality of energy channels, a respective plurality of the projection images of the breast taken at different view angles;

a computer processor configured to apply computer algorithms to the projection images and produce a respective differential phase 3D reconstruction image of the breast for each of the plurality of energy channels; and

said computer processor being further configured to combine the plurality of differential phase 3D reconstruction images to thereby produce one or more output images of the breast; and

a computer display configured to display the one or more of the output images of the breast;

wherein said computer processor is configured to combine the plurality of differential phase 3D reconstruction images in a process that includes assigning different weights to the images being combined.

15. The system of claim 14, wherein said computer processor is configured to combine the plurality of differential phase 3D reconstruction images in a process that includes assigning different colors to the images being combined.

16. The system of claim 15, wherein the computer processor is configured to assign the different colors by applying a two-dimensional matrix of color weighting coefficients to the images being combined.

17. The system of claim 14, wherein the computer processor is configured to produce an output image that is a three-dimensional (3D) matrix of attenuation coefficients of breast tissue voxels.

18. The system of claim 14, wherein the computer processor is configured to produce an output image that is a three-dimensional (3D) matrix of phase coefficients of breast tissue voxels.

19. The system of claim 14, wherein the grating system comprises a stepping source grating that is between the x-ray source and the breast and is configured to vary the spacing between the source grating and the x-ray source for different portions of the rotation of the imaging beam of x-rays.

20. The system of claim 19, wherein the grating system comprises a motorized drive configured to move the source grating linearly along the imaging x-ray beam to vary said spacing.

21. The system of claim 19, wherein the source grating comprises a multi-branch arrangement of individual source grating configured to rotate around an axis of the imaging beam to thereby place a respective source grating at a respective different distance from the source for different portions of the rotation of the imaging beam around the breast.

22. The system of claim 14, wherein the grating system comprises a phase grating and an analyzer grating that are between the breast and the detector and are misaligned to thereby produce a Moire pattern at the detector.

23. The system of claim 14, further comprising an imaging system that is in addition to said gantry and is configured to image the breast using a different imaging modality to determine a region of interest in the breast, and wherein said gantry is configured to select a relative position between the imaging beam and the breast determined by said region of interest.

24. The system of claim 23 in which the different imaging modality is CT imaging other than differential phase imaging.

25. The system of claim 14, wherein the computer processor configured to combine the plurality of differential phase 3D reconstruction images to thereby produce one or more output images of the breast is further configured to produce an output image resolving sub-micron structures in the breast.

26. A method of cone beam CT imaging of an object, comprising:

acquiring projection images of the object taken at different view angles by using a polychromatic x-ray source irradiating the object with an imaging beam, an energy-resolving detector having a plurality of energy channels receiving the imaging beam after passage thereof through the object, and a grating system;

said acquiring comprising acquiring, for each of the plurality of energy channels of the detector, a respective plurality of the projection images of the object taken at different view angles;

performing three-dimensional (3D) computed tomography reconstructions of the object for each of the plurality of energy channels to produce a respective plurality of differential phase contrast 3D reconstruction images of the object; and

combining the plurality of differential phase 3D reconstruction images to thereby produce one or more output images of the object;

wherein said combining of the plurality of differential phase 3D reconstruction images comprises assigning different weights to the images being combined.

27. The method of claim 26, wherein said combining of the plurality of differential phase 3D reconstruction images comprises assigning different colors to the images being combined.

28. The method of claim 27, wherein the assigning of different colors comprises applying a two-dimensional matrix of color weighting coefficients to the images being combined.

29. The method of claim 26, wherein the combining produces the output image comprising three-dimensional (3D) matrix of attenuation coefficients of object voxels.

30. The method of claim 26, wherein the combining produces an output image comprising a three-dimensional (3D) matrix of phase coefficients of object voxels.

31. The method of claim 26, including stepping a source grating, which is between the x-ray source and the object, to thereby vary the spacing of the source grating from the x-ray source for different portions of said acquisition.

32. The method of claim 31, wherein the stepping comprises moving the source grating linearly along the imaging x-ray beam.

33. The method of claim 31, wherein the stepping comprises moving, to a different position between the x-ray source and the object for different portions of said acquisition, a source grating mounted on a respective branch of a multi-branch source grating mechanism.

34. The method of claim 33, wherein the stepping comprises rotating the multi-branch source grating mechanism about an axis of the imaging x-ray beam.

35. The method of claim 26 in which the grating system comprises a phase grating and an analyzer grating that are between the object and the detector, and said acquiring comprises acquiring the projection images while the phase and analyzer grating are misaligned to thereby produce a Moire pattern at the detector.

36. The method of claim 26, further comprising the following steps carried out before said acquiring of the projection images with the polychromatic source:

imaging the object using a different imaging modality to determine a region of interest in the object; and

selecting a relative position between the imaging beam from the polychromatic x-ray source and the object determined by said region of interest and then carrying out the steps recited in claim 26.

37. The method of claim 36 in which the different imaging modality is CT imaging other than differential phase imaging.

38. The method of claim 26, wherein the combining of the 3D reconstruction images comprises producing a combined image resolving sub-micron structures in the object.