Method for image reconstruction, software for image reconstruction, a recording medium therefor, and a radiographic apparatus

• US 6,665,369 B2
• Filed: 06/27/2002
• Issued: 12/16/2003
• Est. Priority Date: 07/13/2001
• Status: Expired due to Fees

• Current Assignee: Shimadzu Corporation
• Original Assignee: Shimadzu Corporation
• Inventors: Ukita, Masaaki
• Primary Examiner(s): BRUCE, DAVID VERNON
• Application Number:
  US10/180,485
• Publication Number:
  US 20030016791A1
• Time in Patent Office: 537 Days
• Field of Search: 378/4, 378/8, 378/19, 378/901
• US Class Current: 378/4
• 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: Y10S 378/901 Computer tomography program or processor

Abstract

An X-ray tube (X-ray focus) and an X-ray detector opposed to each other across an object synchronously scan the object to acquire radiographic data in each scan position. The radiographic data or data resulting from a filtering process of the radiographic data is projected back to a two-dimensional or three-dimensional reconstruction area virtually set to a region of interest of the object. Reconstruction software is used for causing a computer to perform reconstruction computations for each unit area (block) formed by dividing the reconstruction area. The reconstruction computations are performed successively for one unit area (block) after another in a way optimal to cache size. Data in cache memory are reused at an increased rate, and access to data in memory is reduced to shorten a time consumed by the reconstruction computations.

Claims

1. Reconstructing software for performing back projection computations to project radiographic data of an object acquired in each scan position back to a reconstruction area, said software comprising the step of:

causing the back projection computations to be performed, for each unit area formed by dividing said reconstruction area, for projecting said radiographic data acquired in each scan position, or data resulting from filtering of said radiographic data, back to a two-dimensional or three-dimensional reconstruction area virtually set to a region of interest of said object, said radiographic data being acquired by causing a radiation source and a detector arranged opposite each other across said object to scan said object synchronously, or to scan said object synchronously with rotation of said object, said radiation source irradiating said object with electromagnetic waves capable of penetrating said object, said detector detecting electromagnetic waves transmitted through said object.

2. Reconstruction software as defined in claim 1, wherein each said unit area has a square, rectangular, triangular, lozenge-shaped, trapezoidal or other polygonal shape where the reconstruction area is two-dimensional, and a cubic, rectangular parallelepiped, trigonal pyramid, circular cone or other solid shape where the reconstruction area is three-dimensional.

3. Reconstructing software as defined in claim 1, wherein each said unit area is varied in orientation to be long in a direction of back projection.

4. Reconstruction software as defined in claim 1, wherein the back projection computations are performed for each unit area successively in respect of radiographic data corresponding to a plurality of positions among all scan positions.

5. Reconstruction software as defined in claim 1, wherein said unit areas have different sizes between central parts and peripheral parts of said reconstruction area.

6. Reconstructing software as defined in claim 1, wherein the data are successively projected back first to one unit area and then to an adjacent unit area.

7. Reconstructing software as defined in claim 1, wherein the data are projected back to a plurality of back projection points in said unit area, first to one back projection point and then to an adjacent back projection point.

8. Reconstruction software as defined in claim 1, wherein said radiographic data after a filtering process are projected, without interpolation, back to said unit areas.

9. Reconstructing software as defined in claim 1, wherein said reconstruction area is an enlarged reconstruction area divided to have a pixel density higher than a detector pixel density at the center of revolution.

10. Reconstruction software as defined in claim 2, wherein said unit areas have different sizes between central parts and peripheral parts of said reconstruction area.

11. Reconstruction software as defined in claim 2, wherein the data are successively projected back first to one unit area and then to an adjacent unit area.

12. Reconstruction software as defined in claim 2, wherein the data are projected back to a plurality of back projection points in said unit area, first to one back projection point and then to an adjacent back projection point.

13. Reconstruction software as defined in claim 3, wherein said unit areas have different sizes between central parts and peripheral parts of said reconstruction area.

14. Reconstructiong software as defined in claim 3, wherein the data are successively projected back first to one unit area and then to an adjacent unit area.

15. Reconstruction software as defined in claim 3, wherein the data are projected back to a plurality of back projection points in said unit area, first to one back projection point and then to an adjacent back projection point.

16. Reconstruction software as defined in claim 4, wherein said unit areas have different sizes between central parts and peripheral parts of said reconstruction area.

17. Reconstruction software as defined in claim 4, wherein the data are successively projected back first to one unit area and then to an adjacent unit area.

18. Reconstructing method for performing back projection computations to project radiographic data of an object acquired in each scan position back to a reconstruction area, said method comprising the step of:

causing the back projection computations to be performed, for each unit area formed by dividing said reconstruction area, for projecting said radiographic data acquired in each scan position, or data resulting from filtering of said radiographic data, back to a two-dimensional or three-dimensional reconstruction area virtually set to a region of interest of said object, said radiographic data being acquired by causing a radiation source and a detector arranged opposite each other across said object to scan said object synchronously, or to scan said object synchronously with rotation of said object, said radiation source irradiating said object with electromagnetic waves capable of penetrating said object, said detector detecting electromagnetic waves transmitted through said object.

19. A radiographic apparatus for generating two-dimensional or three-dimensional reconstruction images of a region of interest by using reconstruction software to perform back projection computations, wherein:

said reconstruction software comprises the step of causing the back projection computations to be performed, for each unit area formed by dividing said reconstruction area, for projecting said radiographic data acquired in each scan position, or data resulting from filtering of said radiographic data, back to a two-dimensional or three-dimensional reconstruction area virtually set to a region of interest of said object, said radiographic data being acquired by causing a radiation source and a detector arranged opposite each other across said object to scan said object synchronously, or to scan said object synchronously with rotation of said object, said radiation source irradiating said object with electromagnetic waves capable of penetrating said object, said detector detecting electromagnetic waves transmitted through said object.

20. A storage medium recording section reconstructing software and readable by a computer, wherein:

said reconstruction software comprises the step of causing the back projection computations to be performed, for each unit area formed by dividing said reconstruction area, for projecting said radiographic data acquired in each scan position, or data resulting from filtering of said radiographic data, back to a two-dimensional or three-dimensional reconstruction area virtually set to a region of interest of said object, said radiographic data being acquired by causing a radiation source and a detector arranged opposite each other across said object to scan said object synchronously, or to scan said object synchronously with rotation of said object, said radiation source irradiating said object with electromagnetic waves capable of penetrating said object, said detector detecting electromagnetic waves transmitted through said object.