System and method for image reconstruction in a cone beam imaging system

• US 6,574,297 B2
• Filed: 10/30/2001
• Issued: 06/03/2003
• Est. Priority Date: 10/30/2001
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens Corporate Research Incorporated (Siemens AG)
• Inventors: Tam, Kwok
• Primary Examiner(s): BRUCE, DAVID VERNON
• Application Number:
  US10/015,716
• Publication Number:
  US 20030081715A1
• Time in Patent Office: 581 Days
• Field of Search: 378/4, 378/8, 378/15, 378/901
• US Class Current: 378/15
• CPC Class Codes: A61B 6/027 characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral
• CPC Class Codes: G06T 11/005 Specific pre-processing for tomographic reconstruction, e.g. calibration, source positioning, rebinning, scatter correction, retrospective gating
• CPC Class Codes: G06T 2211/432 Truncation
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

A system and method for accurately reconstructing an image of a ROI (region of interest) within a long object by removing components associated with data contamination. In one aspect, an image reconstruction method comprises collecting a set of image data along a spiral scan path of a ROI (region of interest) portion of an object, identifying contaminated data within the collected set of image data, the contaminated data corresponding to image data associated with an object outside the ROI, and reconstructing an image of the ROI using the set of image data less the contaminated data.

Claims

1. An image reconstruction method comprising the steps of:

collecting a set of image data along a spiral scan path of a ROI (region of interest) portion of an object;

identifying contaminated data within the collected set of image data, the contaminated data corresponding to image data associated with an object outside the ROI; and

reconstructing an image of the ROI using the set of image data less the contaminated data.

2. The method of claim 1, wherein the step of identifying comprises identifying a source position near a beginning or end portion of the spiral scan path.

3. The method of claim 1, wherein the step of identifying comprises identifying a first complete sinusoidal stage near a beginning portion of the ROI and a second complete sinusoidal stage near an ending portion of the ROI, wherein a complete sinusoidal stage comprises source positions scanning an angular range of B.

4. The method of claim 3, wherein the step of identifying the first and second complete sinusoidal stages comprises projecting the spiral path on a plane in Radon space.

5. The method of claim 3, wherein the step of identifying contaminated data comprises identifying image data associated with a source position that lies on an incomplete sinusoidal stage.

6. A scanning and data acquisition method for three dimensional (3D) computerized tomographic (CT) imaging of a region-of-interest (ROI) in an object, wherein image reconstruction processing is applied to a plurality of sets of 2D cone beam projection data, each set being acquired by irradiation of the object by energy from a cone beam source that is directed to a 2D detector at a corresponding plurality of scan path source positions, comprising the steps of:

applying a mask to each set of the projection data so that data inside the boundaries of each mask form a corresponding plurality of masked 2D data sets;

ramp filtering each masked 2D data set along a plurality of parallel lines formed therein, to generate a corresponding plurality of filtered 2D data, each filtered 2D data set corresponding to a calculation of a first estimate of Radon derivative data determined from a given set of the 2D cone beam projection data;

generating 2D correction data for each of the first estimates of Radon derivative data by processing portions of the given set of cone beam projection data that are adjacent boundaries of the mask, wherein the step of generating 2D correction data is not performed for cone beam projection data that is associated with objects outside a region of interest; and

combining each filtered 2D data set and the 2D correction data calculated therefore, in a weighted 3D backprojection manner into a 3D space, thereby reconstructing a 3D image of the ROI in the object.

7. The method of claim 6, comprising the step of identifying contaminated data within the set of cone beam projection data, the contaminated data corresponding to cone beam projection data associated with an object outside the ROI.

8. The method of claim 7, wherein the step of identifying comprises identifying a source position near a beginning or end portion of the spiral scan path.

9. The method of claim 7, wherein the step of identifying comprises identifying a first complete sinusoidal stage near a beginning portion of the ROI and a second complete sinusoidal stage near an ending portion of the ROI, wherein a complete sinusoidal stage comprises source positions scanning an angular range of B.

10. The method of claim 9, wherein the step of identifying the first and second complete sinusoidal stages comprises projecting the spiral path on a plane in Radon space.

11. The method of claim 9, wherein the step of identifying contaminated data comprises identifying image data associated with a source position that lies on an incomplete sinusoidal stage.

12. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for performing three dimensional (3D) computerized tomographic (CT) image reconstruction of a region-of-interest (ROI) in an object, wherein image reconstruction processing is applied to a plurality of sets of 2D cone beam projection data, each set being acquired by irradiation of the object by energy from a cone beam source that is directed to a 2D detector at a corresponding plurality of scan path source positions, the method steps comprising:

applying a mask to each set of the projection data so that data inside the boundaries of each mask form a corresponding plurality of masked 2D data sets;

ramp filtering each masked 2D data set along a plurality of parallel lines formed therein, to generate a corresponding plurality of filtered 2D data, each filtered 2D data set corresponding to a calculation of a first estimate of Radon derivative data determined from a given set of the 2D cone beam projection data;

generating 2D correction data for each of the first estimates of Radon derivative data by processing portions of the given set of cone beam projection data that are adjacent boundaries of the mask, wherein the step of generating 2D correction data is not performed for cone beam projection data that is associated with objects outside a region of interest; and

combining each filtered 2D data set and the 2D correction data calculated therefore, in a weighted 3D backprojection manner into a 3D space, thereby reconstructing a 3D image of the ROI in the object.

13. The program storage device of claim 12, comprising instructions for performing the step of identifying contaminated data within the set of cone beam projection data, the contaminated data corresponding to cone beam projection data associated with an object outside the ROI.

14. The program storage device of claim 13, wherein the instructions for performing the step of identifying comprise instructions for identifying a source position near a beginning or end portion of the spiral scan path.

15. The program storage device of claim 13, wherein the instructions for performing the step of identifying comprise instructions for identifying a first complete sinusoidal stage near a beginning portion of the ROI and a second complete sinusoidal stage near an ending portion of the ROI, wherein a complete sinusoidal stage comprises source positions scanning an angular range of B.

16. The program storage device of claim 15, wherein the instructions for performing the step of identifying the first and second complete sinusoidal stages comprise instructions for projecting the spiral path on a plane in Radon space.

17. The program storage device of claim 15, wherein the instructions for performing the step of identifying contaminated data comprise instructions for identifying image data associated with a source position that lies on an incomplete sinusoidal stage.

18. An apparatus for three dimensional (3D) computerized tomographic (CT) imaging of a region-of-interest (ROI) in an object, comprising:

a cone beam source for applying radiation energy to at least the ROI of the object;

a 2D area detector for detecting radiation energy;

means for defining a source scanning trajectory as a scan path traversed by the source;

a manipulator for causing the cone beam source, fixed relative to an area detector with both source and detector movably positioned relative to the object, to scan about the ROI in the object at a plurality of source positions in a direction along the scan path to cause said area detector to acquire a set of 2D cone beam projection data at each of said source positions;

a masking means for applying a mask to each set of the 2D cone beam projection data to generate masked data sets;

a ramp filtering means for ramp filtering each masked 2D data set along a plurality of parallel lines formed therein, to generate a corresponding plurality of filtered 2D data, each filtered 2D data set corresponding to a calculation of a first estimate of Radon derivative data determined from a given set of the 2D cone beam projection data;

processing means for developing 2D correction data for each of the first estimates of Radon derivative data by processing portions of the given set of 2D cone beam projection data that are adjacent boundaries of the mask, wherein 2D correction data is not generated for cone beam projection data that is associated with objects outside a region of interest; and

3D backprojection means for combining each filtered 2D data set and the 2D correction data calculated therefore, in a weighted 3D backprojection manner into a 3D space, thereby reconstructing a 3D image of the ROI in the object.