IMAGE RECONSTRUCTION METHOD AND X-RAY CT APPARATUS

• US 20070211846A1
• Filed: 03/09/2007
• Published: 09/13/2007
• Est. Priority Date: 03/10/2006
• Status: Active Grant

• Current Assignee: GE Medical Systems Global Technology Company LLC (GE Healthcare Technologies, Inc.)
• Original Assignee: GE Medical Systems Global Technology Company LLC (GE Healthcare Technologies, Inc.)
• Inventors: Zhou, Yu, Li, Wu
• Granted Patent: US 7,656,991 B2
• Time in Patent Office: Days
• US Class Current: 378/4
• CPC Class Codes: A61B 6/027 characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral
• CPC Class Codes: A61B 6/04 Positioning of patients; Tiltable beds or the like operating tables A61G13/00; operating chairs A61G15/00
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: G06T 11/006 Inverse problem, transformation from projection-space into object-space, e.g. transform methods, back-projection, algebraic methods
• CPC Class Codes: G06T 2211/424 Iterative
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

The present invention is intended to provide an image reconstruction method based on an iterative reconstruction technique and characterized by a short image reconstruction time, a small memory capacity, and high image quality. The image reconstruction method comprises the steps of: constructing a system model that has a plurality of concentric rings each segmented into a plurality of sectors; constructing a system matrix associated with one view, by using some of all the sectors constituting the system model, the some of all sectors being located on respective projection lines concerning the one view; creating a system matrix associated with another view, by transforming the system matrix associated with the one view; reconstructing an image through iterative reconstruction by using the system matrix and projection data; and transforming the image into an image composed of rectangular pixels.

Claims

1. An image reconstruction method, comprising the steps of:

constructing a system model that has a plurality of concentric rings each segmented into a plurality of sectors;

constructing a system matrix associated with one view, by using some of all the sectors constituting the system model, the some of all sectors being located on respective projection lines concerning the one view;

creating a system matrix associated with another view, by transforming the system matrix associated with the one view;

reconstructing an image through iterative reconstruction by using the system matrix and projection data; and

transforming the image into an image composed of rectangular pixels.

2. The image reconstruction method according to claim 1, wherein each of elements constituting the system matrix is a length of a projection line falling within each sector.

3. The image reconstruction method according to claim 1, wherein each of elements constituting the system matrix is a partial area of a projection stripe falling within each sector.

4. The image reconstruction method according to claim 3, wherein the partial area is a normalized area.

5. The image reconstruction method according to claim 1, wherein the creation of a system matrix to be associated with another view is performed at every time of iteration.

6. The image reconstruction method according to claim 1, wherein an ordered subsets expectation maximization (OSEM) technique is adopted as the iterative reconstruction technique.

7. The image reconstruction method according to claim 1, wherein the transformation into an image composed of rectangular pixels is achieved through bilinear interpolation.

8. The image reconstruction method according to claim 1, wherein the projection lines express fan-beam X-rays.

9. The image reconstruction method according to claim 1, wherein the projection lines express parallel-beam X-rays.

10. An X-ray CT apparatus including data acquisition equipment that scans a subject with X-rays so as to acquire projection data, and image reconstruction equipment that reconstructs an image on the basis of the acquired projection data, wherein:

the image reconstruction equipment comprises;

a system model construction device for constructing a system model that has a plurality of concentric rings each segmented into a plurality of sectors;

a system matrix construction device for constructing a system matrix associated with one view, by using some of all the sectors constituting the system model, the some of all the sectors being located on respective projection lines concerning the one view;

a system matrix creation device for creating a system matrix associated with another view, by transforming the system matrix associated with the one view;

an image reconstruction device that reconstructs an image through iterative reconstruction by using the system matrix and projection data; and

a transformation device for transforming the image into an image composed of rectangular pixels.

11. The X-ray CT apparatus according to claim 10, wherein each of elements constituting the system matrix is a length of a projection line falling within each sector.

12. The X-ray CT apparatus according to claim 10, wherein each of elements constituting the system matrix is a partial area of a projection stripe falling within each sector.

13. The X-ray CT apparatus according to claim 12, wherein the partial area is a normalized area.

14. The X-ray CT apparatus according to claim 10, wherein the system matrix creation device creates a system matrix to be associated with another view at every time of iteration.

15. The X-ray CT apparatus according to claim 10 wherein an ordered subsets expectation maximization (OSEM) technique is adopted as the iterative reconstruction technique.

16. The X-ray CT apparatus according to claim 10, wherein the transformation device transforms an image into an image composed of rectangular pixels through bilinear interpolation.

17. The X-ray CT apparatus according to claim 10, wherein the projection lines express fan-beam X-rays.

18. The X-ray CT apparatus according to claim 10, wherein the projection lines express parallel-beam X-rays.

19. A method for reconstructing an image of an object, said method comprising:

generating a plurality of projection data;

generating a system model using the imaging data, wherein the system model includes a plurality of concentric rings;

generating a partial system matrix using the system model; and

using the projection data and the partial system matrix to iteratively reconstruct an image of the object that includes a plurality of radial sectors.

20. A method in accordance with claim 19 further comprising transforming the reconstructed image into a final image that includes a plurality of rectangular pixels.