X-ray computed tomography apparatus, reconstruction processing apparatus, and image processing apparatus

1. An X-ray computed tomography apparatus comprising:

a scanning unit which includes an X-ray tube and an X-ray detector for scanning a subject to be examined with cone beam X-rays;

a reconstruction unit which generates first image data on the basis of output data from the scanning unit;

an extraction unit which extracts a cone beam artifact component contained in the first image data, on the basis of a typical shape and typical direction of the cone beam artifact; and

a subtraction unit which generates second image data with a reduced cone beam artifact by subtracting the cone beam artifact component from the first image data.

2. The apparatus according to claim 1 , wherein the reconstruction unit generates the first image data by performing Feldkamp reconstruction of the output data.

3. The apparatus according to claim 1 , wherein the extraction unit extracts the cone beam artifact component by performing filtering for at least one of the output data and the first image data.

4. The apparatus according to claim 1 , wherein the extraction unit generates third image data comprising an edge component in a body axis direction of the subject as the cone beam artifact component on the basis of at least one of the output data and the first image data.

5. The apparatus according to claim 4 , wherein the extraction unit performs low-pass filtering for the output data in the body axis direction, generates fourth image data on the basis of output data having undergone low-pass filtering in the body axis direction, and generates the third image data by subtracting the generated fourth image data from the first image data.

6. The apparatus according to claim 4 , wherein the extraction unit generates the third image data by performing high-pass filtering for the first image data in the body axis direction.

7. The apparatus according to claim 1 , wherein the extraction unit extracts the cone beam artifact component by suppressing an edge component in a plane substantially perpendicular to the body axis direction which is contained in third image data comprising the edge component in the body axis direction of the subject.

8. The apparatus according to claim 1 , wherein the extraction unit extracts the cone beam artifact component by performing low-pass filtering in a plane substantially perpendicular to the body axis direction of the subject for third image data comprising an edge component in the body axis direction of the subject.

9. The apparatus according to claim 1 , wherein the extraction unit extracts the cone beam artifact component by removing a living body component contained in third image data comprising an edge component in the body axis direction of the subject.

10. The apparatus according to claim 1 , wherein the extraction unit extracts the cone beam artifact component by performing threshold processing for third image data comprising an edge component in the body axis direction of the subject on the basis of a pixel value which the cone beam artifact component has.

11. The apparatus according to claim 1 , wherein the extraction unit performs low-pass filtering for the output data in the body axis direction of the subject, generates fourth image data on the basis of the output data having undergone low-pass filtering in the body axis direction, generates the third image data by subtracting the generated fourth image data from the first image data, and extracts the cone beam artifact component by performing low-pass filtering in a plane substantially perpendicular to the body axis direction for the generated third image data.

12. The apparatus according to claim 1 , wherein the extraction unit generates fourth image data by performing high-pass filtering for the first image data in the body axis direction of the subject, generates the third image data by subtracting the generated fourth image data from the first image data, and extracts the cone beam artifact component by performing low-pass filtering in a plane substantially perpendicular to the body axis direction for the generated third image data.

13. The apparatus according to claim 1 , further comprising a weighting processing unit which performs weighting with a distribution of weights changing in accordance with positions in the body axis direction for the cone beam artifact component.

14. The apparatus according to claim 13 , wherein the weighting processing unit performs the weighting with the distribution of weights gradually increasing from a center to edges in the body axis direction.

15. The apparatus according to claim 1 , wherein the X-ray detector includes not less than 64 X-ray detection element rows arrayed along the body axis direction of the subject.

16. A reconstruction processing apparatus comprising:

a storage unit which stores projection data acquired by scanning a subject to be examined with cone beam X-rays;

a reconstruction unit which generates first image data on the basis of the projection data;

an extraction unit which extracts a cone beam artifact component contained in the generated first image data on the basis of a typical shape and a typical direction of the cone beam artifact; and

a subtraction unit which generates second image data with a reduced cone beam artifact component by subtracting the extracted cone beam artifact from the first image data.

17. An image processing apparatus comprising:

a storage unit which stores first image data generated on the basis of projection data acquired by scanning a subject to be examined with cone beam X-rays;

an extraction unit which extracts a cone beam artifact component contained in the first image data on the basis of a typical shape and typical direction of the cone beam artifact; and

a subtraction unit which generates second image data with a reduced cone beam artifact component by subtracting the extracted cone beam artifact component from the first image data.