Projection data correction and computed tomography value computation

1. A method for correcting projection data generated from a computed tomography (CT) examination of an object, comprising:

acquiring the projection data of the object;

generating a CT image of the object based upon the projection data;

segmenting the CT image to identify a set of sub-objects within the object, wherein the set of sub-objects comprises a first sub-object and a second sub-object;

determining a first z-effective value for the first sub-object and a second z-effective value for the second sub-object; and

performing a beam hardening correction upon the projection data using at least one of the first z-effective value or the second z-effective value to obtain corrected projection data.

2. The method of claim 1 , comprising:

generating an updated CT image of the object based upon the corrected projection data.

3. The method of claim 2 , the generating a CT image comprising generating the CT image utilizing a first reconstruction algorithm and the generating an updated CT image comprising generating the updated CT image utilizing a second reconstruction algorithm different than the first reconstruction algorithm.

4. The method of claim 1 , comprising:

assigning a background CT value to one or more voxels of the CT image that do not represent at least one object within the set of sub-objects.

5. The method of claim 2 , comprising:

comparing the CT image with the updated CT image; and

generating a blended CT image of the CT image and the updated CT image based upon results of the comparing the CT image with the updated CT image.

6. The method of claim 2 , comprising:

segmenting the updated CT image to identify a second set of sub-objects, wherein the second set of sub-objects comprise a third sub-object and a fourth sub-object;

determining an initial CT value for the third sub-object and an initial CT value for the fourth sub-object;

applying the initial CT value for the third sub-object to voxels of the updated CT image representative of the third sub-object and the initial CT value for the fourth sub-object to voxels of the updated CT image representative of the fourth sub-object to generate a synthetic CT image;

forward modeling the synthetic CT image to generate synthetic CT projection data;

comparing the synthetic CT projection data to the corrected projection data; and

updating at least one of the initial CT value for the third sub-object or the initial CT value for the fourth sub-object based upon results of the comparing.

7. The method of claim 1 , the beam hardening correction comprising:

identifying a ray intersecting the first sub-object and the second sub-object;

generating a beam hardening correction parameter based upon at least one of the first z-effective value or the second z-effective value; and

correcting a projection value, within the projection data, for the ray based upon the beam hardening correction parameter.

8. The method of claim 7 , the generating a beam hardening correction parameter comprising:

determining a first weight for the first z-effective value based upon at least one of a density of the first sub-object or a pass length of the ray through the first sub-object;

determining a second weight for the second z-effective value based upon at least one of a density of the first sub-object or a pass length of the ray through the first sub-object;

applying the first weight to the first z-effective value to obtain a weighted first z-effective value; and

applying the second weight to the second z-effective value to obtain a weighted second z-effective value, wherein the beam hardening correction parameter is computed based upon at least one of the weighted first z-effective value or the weighted second z-effective value.

9. The method of claim 1 , the determining a first z-effective value for the first sub-object and a second z-effective value for the second sub-object comprising:

determining an initial z-effective value for the first sub-object and an initial z-effective value for the second sub-object;

applying the initial z-effective value for the first sub-object to voxels of the CT image representative of the first sub-object and the initial z-effective value for the second sub-object to voxels of the CT image representative of the second sub-object to generate a z-effective image;

forward modeling the z-effective image to generate synthetic multi-energy projection data;

comparing the synthetic multi-energy projection data to the projection data; and

updating at least one of the initial z-effective value for the first sub-object and the initial z-effective value for the second sub-object based upon results of the comparing.

10. The method of claim 1 , the performing beam hardening correction comprising:

utilizing a polynomial function to obtain the corrected projection data.

11. A system for correcting projection data generated from a computed tomography (CT) examination of an object, comprising:

an image generator configured to:

generate a CT image of the object based upon projection data of the object;

segment the CT image to identify a set of sub-objects within the object, where the set of sub-objects comprises a first sub-object and a second sub-object;

determine a first z-effective value for the first sub-object and a second z-effective value for the second sub-object; and

perform a beam hardening correction upon the projection data using at least one of the first z-effective value or the second z-effective value to obtain corrected projection data.

12. A method for correcting projection data generated from a computed tomography (CT) examination of an object, comprising:

segmenting a CT image to identify a first sub-object within an object under examination;

determining a first z-effective value for the first sub-object; and

performing a beam hardening correction upon projection data from which the CT image was generated to obtain corrected projection data, comprising:

calculating a first weight as a function of a pass length, through the first sub-object, of a ray;

applying the first weight to the first z-effective value to obtain a weighted first z-effective value;

computing a beam hardening correction parameter based upon the weighted first z-effective value; and

correcting a projection value corresponding to the ray based upon the beam hardening correction parameter.

13. The method of claim 12 , wherein:

the segmenting comprises segmenting the CT image to identify a second sub-object intersected by the ray,

the determining comprises determining a second z-effective value for the second sub-object,

the calculating comprises calculating a second weight as a function of a pass length, through the second sub-object, of the ray,

the applying comprises applying the second weight to the second z-effective value to obtain a weighted second z-effective value, and

the computing comprises computing the beam hardening correction parameter based upon the weighted second z-effective value.

14. The method of claim 12 , comprising:

generating an updated CT image of the object based upon the corrected projection data.

15. The method of claim 14 , comprising:

blending one or more voxels of the CT image with one or more voxels of the updated CT image.

16. The method of claim 12 , comprising:

reconstructing the CT image from the projection data.

17. The method of claim 12 , wherein the performing comprises:

utilizing a polynomial function to obtain the corrected projection data.

18. The method of claim 12 , wherein the determining comprises:

generating a z-effective image from the projection data; and

segmenting the z-effective image to identify the first sub-object.

19. The method of claim 18 , wherein:

the segmenting a CT image comprises segmenting the CT image to identify a first set of sub-objects,

the segmenting the z-effective image comprises segmenting the CT image to identify a second set of sub-objects, and

the determining comprises correlating the first set of sub-objects with the second set of sub-objects.

20. The method of claim 12 , comprising:

using the projection data to generate the CT image and a z-effective image; and

determining the first z-effective value from the z-effective image.