System and method of image artifact reduction in fast kVp switching CT

• US 8,363,917 B2
• Filed: 10/14/2009
• Issued: 01/29/2013
• Est. Priority Date: 10/14/2009
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Fan, Jiahua, Chandra, Naveen, Johnson, Andrew, Hsieh, Jiang, Dong, Fang, Kulpins, Mary Sue, Crandall, Peter
• Primary Examiner(s): Taningco, Alexander H
• Application Number:
  US12/578,886
• Publication Number:
  US 20110085719A1
• Time in Patent Office: 1,203 Days
• Field of Search: 378/5, 378/57, 378/98.9, 382/131
• US Class Current: 382/131
• CPC Class Codes: G06T 11/008 Specific post-processing after tomographic reconstruction, e.g. voxelisation, metal artifact correction
• CPC Class Codes: G06T 2211/408 Dual energy

Abstract

A CT system includes a generator configured to energize an x-ray source to a first kilovoltage (kVp) and to a second kVp, and a computer that is programmed to acquire a first view dataset with the x-ray source energized to the first kVp and a second view dataset with the x-ray source energized to the second kVp, generate a base correction image using the first view dataset and the second view dataset, and reconstruct a pair of base material images from the first view dataset and from the second view dataset. The computer is also programmed to estimate artifact correlation in the pair of base material images using the base correction image, generate a pair of final base material images and a final monochromatic image, and correct one of the pair of final base material images and the final monochromatic image at a keV value using the estimated artifact correlation.

Claims

1. A CT system comprising:

a rotatable gantry having an opening for receiving an object to be scanned;

an x-ray source coupled to the gantry and configured to project x-rays through the opening;

a generator configured to energize the x-ray source to a first kilovoltage (kVp) and to a second kVp to generate the x-rays;

a detector having pixels therein, the detector attached to the gantry and positioned to receive the x-rays; and

a computer programmed to;

acquire a first view dataset with the x-ray source energized to the first kVp and a second view dataset with the x-ray source energized to the second kVp;

generate a base correction image using the first view dataset and the second view dataset;

reconstruct a pair of base material images from the first view dataset and from the second view dataset;

estimate artifact correlation in the pair of base material images using the base correction image;

generate a pair of final base material images and a final monochromatic image; and

correct one of the pair of final base material images and the final monochromatic image at a keV value using the estimated artifact correlation.

2. The CT system of claim 1 wherein the computer is programmed to generate the final monochromatic image at the keV value after correcting the pair of final base material images.

3. The CT system of claim 2 wherein the final monochromatic image is in an energy range between 40 keV and 140 keV.

4. The CT system of claim 1 wherein the computer, in being programmed to generate the base correction image, is programmed to generate a monochromatic raw image from the first view dataset and from the second view dataset.

5. The CT system of claim 4 wherein the computer is programmed to generate the monochromatic raw image within a range of monochromatic energy between 65 keV and 75 keV.

6. The CT system of claim 4 wherein the computer is programmed to:

separate soft tissue and high attenuation materials;

forward project one or more separated high attenuation materials;

generate corrections of the one or more forward projected high attenuation materials; and

generate a filtered back-projection using the correction of the one or more forward projected high attenuation materials.

7. The CT system of claim 6 wherein the computer, in being programmed to generate the correction, is programmed to generate a polynomial correction.

8. A method of acquiring CT imaging data, the method comprising:

reconstructing at least two base material images using high and low peak kilovoltage (kVp) CT imaging datasets;

generating a monochromatic raw image from the high and low kVp CT imaging datasets;

applying one or more parallel beam forward projections to the monochromatic raw image;

applying a correction to each of the one or more parallel beam forward projections;

summing the corrected one or more parallel beam forward projections to generate a sum of projections;

applying a filtered back-projection to the sum of projections using a prescribed field-of-view, to generate a base corrected image; and

estimating artifact correlation based on the base corrected image.

9. The method of claim 8 wherein generating the monochromatic raw image comprises generating the monochromatic raw image at an energy between a range of approximately 65 keV and 75 keV.

10. The method of claim 8 wherein estimating artifact correlation comprises estimating artifact correlation in the at least two base material images based on the base corrected image.

11. The method of claim 8 comprising generating a final monochromatic image using the at least two base material images.

12. The method of claim 11 wherein estimating artifact correlation comprises estimating artifact correlation to the final monochromatic image based on the base corrected image.

13. The method of claim 11 wherein the final monochromatic image is an image of an energy between 40 keV and 140 keV.

14. The method of claim 8 comprising:

separating one or more high-attenuation materials from the monochromatic raw image; and

forward projecting the one or more high-attenuation materials to generate the one or more parallel beam forward projections.

15. The method of claim 8 wherein applying the correction comprises applying a polynomial correction.

16. A computer readable storage medium having stored thereon a computer program comprising instructions, which, when executed by a computer, cause the computer to:

acquire high and low peak kilovoltage (kVp) CT imaging datasets;

reconstruct a first base material image and a second base material image from the high and low kVp CT imaging datasets;

generate a raw monochromatic image from the high and low kVp CT imaging datasets;

process the raw monochromatic image to separate a first material at a first given threshold;

forward project the first separated material;

apply projection space processing and a filtered back-projection to the projection of the first separated material to generate a base corrected image; and

correct one of a final monochromatic image and the first and second base material images using the base corrected image.

17. The computer readable storage medium of claim 16 wherein the computer is caused to generate the raw monochromatic image by being caused to:

generate a monochromatic projection from the high and low kVp CT imaging datasets; and

back project a full scan field-of-view of the generated monochromatic projection.

18. The computer readable storage medium of claim 16 wherein the first given threshold corresponds to one of bone and metal.

19. The computer readable storage medium of claim 18 wherein the threshold that corresponds to bone is approximately 200-1000 Hounsfield Units (HU) and wherein the threshold that corresponds to metal is approximately 1000-2000 HU.

20. The computer readable storage medium of claim 16 wherein the computer is caused to:

process the raw monochromatic image to separate a second material at a second given threshold;

forward project the second separated material; and

apply a filtered back-projection to the projection of the second separated material to generate the base corrected image.

21. The computer readable storage medium of claim 16 wherein the computer is caused to:

process the raw monochromatic image to separate a second material at a second given threshold;

forward project the second separated material;

sum the forward projection of the first separated material and of the second separated material; and

apply projection space processing and a filtered back-projection to the sum of the first separated material and of the second separated base material to generate the base corrected image.

22. A method of acquiring CT imaging data, the method comprising:

reconstructing at least two base material images using high and low peak kilovoltage (kVp) CT imaging datasets;

generating a base material raw image from the high and low kVp CT imaging datasets;

applying one or more parallel beam forward projections to the base material raw image;

applying a correction to each of the one or more parallel beam forward projections;

summing the corrected one or more parallel beam forward projections to generate a sum of projections;

applying a filtered back-projection to the sum of projections using a prescribed field-of-view, to generate a base corrected image; and

estimating artifact correlation based on the base corrected image.

23. The method of claim 22 wherein estimating artifact correlation comprises estimating artifact correlation in the at least two base material images based on the base corrected image.

24. The method of claim 22 comprising generating a final monochromatic image using the at least two base material images.

25. The method of claim 22 comprising:

separating one or more high-attenuation materials from the base material raw image; and

forward projecting the one or more high-attenuation materials to generate the one or more parallel beam forward projections.

26. The method of claim 22 wherein applying the correction comprises applying a polynomial correction.