System and method for image reconstruction by using multi-sheet surface rebinning

• US 8,204,173 B2
• Filed: 07/13/2010
• Issued: 06/19/2012
• Est. Priority Date: 04/25/2003
• Status: Active Grant

• Current Assignee: Rapiscan Systems Incorporated (OSI Systems Incorporated)
• Original Assignee: Rapiscan Systems Incorporated (OSI Systems Incorporated)
• Inventors: Betcke, Marta, Lionheart, William Robert Breckon, Morton, Edward James
• Primary Examiner(s): Taningco, Alexander H
• Application Number:
  US12/835,682
• Publication Number:
  US 20110091007A1
• Time in Patent Office: 707 Days
• Field of Search: 378/4, 378/9, 378/10, 378/19
• US Class Current: 378/9
• 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 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4014 arranged in multiple source-detector units
• CPC Class Codes: A61B 6/5205 involving processing of raw data to produce diagnostic data
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]
• CPC Class Codes: G06T 11/005 Specific pre-processing for tomographic reconstruction, e.g. calibration, source positioning, rebinning, scatter correction, retrospective gating

Abstract

The present application is directed toward the generation of three dimensional images in a tomography system having X-ray sources offset from detectors, in particular in a system where the sources are located on a plane, while detectors are located on multiple parallel planes, parallel to the plane of sources and all the planes of detectors lie on one side of the plane of sources. A controller operates to rebin detected X-rays onto a non-flat surface, perform two dimensional reconstruction on the surface, and generate the three dimensional image from reconstructed images on the plurality of surfaces.

Claims

1. A tomography system comprising a plurality of X-ray sources;

a plurality of detectors; and

a controller adapted to process X-rays detected by said plurality of detectors and generate a three dimensional image wherein said controller comprises a plurality of programmatic instructions that, when executed, a) rebin each of said detected X-rays onto a non-flat surface, b) perform a two dimensional reconstruction of said rebinned data on a non-flat surface, and c) generate said three dimensional image from the said reconstructed images on the plurality of said surfaces, wherein said rebinning process further comprises using data from said plurality of detectors to approximate a combination of measured data from at least two intersecting lines and using the combination to solve two or more simultaneous equations to determine values of each point in the three dimensional image such that each point lies in at least one of two surfaces, wherein each of said two surfaces is associated with at least one of the at least two intersecting lines.

2. The controller of claim 1 wherein said controller filters said rebinned data to maximize resolution of said three dimensional image.

3. The controller of claim 1 wherein said rebinning of each of said detected X-ray onto a non-flat surface is achieved by collecting data from X-rays close to a surface with more than one sheet and wherein reconstruction on each said surface is subsequently achieved by applying at least one of a two-dimensional weighted inverse Radon transform or an adapted two- dimensional reconstruction, to combined data from all sheets.

4. The controller of claim 3 wherein the more than two simultaneously solvable equations relate to a plurality of reconstructed superimposed images, one on each of a plurality of multi-sheet surfaces, and a plurality of z-positions of sheets of each multi-sheet surface intersecting each point in a region being imaged.

5. The controller of claim 3 wherein said controller uses said simultaneous equations incorporating the direction point spread functions in an axial direction to improve approximation with detected X-rays which were at least partially not on a rebinning surface.

6. The controller of claim 3 wherein said controller is adapted to perform backprojection without filtering on multi-sheet surfaces;

axial deconvolution; and

subsequently filtering on each transaxial slice of a volume being imaged.

7. The controller of claim 1 wherein said simultaneously solvable equations is solved using at least one of a least squares sense, a minimization of a sum of absolute values of residuals, a minimization of any weighted norm of residuals, a minimization of any weighted norm of residuals wherein said weights are derived from a model of data errors, structured Total Least Norms, Iteratively Reweighted Least Squares and Iteratively Reweighted Norm approaches, or optimization methods including primal-dual methods, gradient methods, gradient projection methods, nonlinear reconstruction methods, with any type of regularization, penalty or constraints.

8. The controller of claim 1 wherein the controller initiates the generation of said three dimensional image after a threshold amount of detected X-ray data are obtained prior to obtaining data for the entire object.

9. The controller of claim 1 wherein the plurality of X-ray sources are stationary.

10. The controller of claim 1, wherein said controller is adapted to correct sinogram data on a rebinning surface using at least one of an optical flow technique or any Partial Differential Equation technique.

11. The system of claim 1 wherein said combination is at least one of a function, an integral or a sum.

12. A method of generating a three dimensional image in a tomography system comprising a plurality of X-ray sources and a plurality of detectors further comprising the steps of:

a) rebinning each of said detected X-rays onto a non-flat surface, b) performing a two dimensional reconstruction of the said rebinned data on a non-flat surface, and c) generating said three dimensional image from the said reconstructed images on the plurality of said surfaces, wherein said rebinning process further comprises using data from said plurality of detectors to approximate a combination of measured data from at least two intersecting lines and using the combination to solve two or more simultaneous equations to determine values of each point in the three dimensional image such that each point lies in at least one of two surfaces, wherein each of said two surfaces is associated with at least one of the at least two intersecting lines.

13. The method of claim 12 further comprising the step of filtering said rebinned data to maximize resolution of said three dimensional image.

14. The method of claim 12 wherein the step of rebinning of each of said detected X-ray onto a non-flat surface is achieved by collecting data from X-rays close to a surface with more than one sheet and wherein the reconstruction on each said surface is subsequently achieved by applying at least one of a two-dimensional weighted inverse Radon transform or an adapted two- dimensional reconstruction, to combined data from all sheets.

15. The method of claim 14 wherein the simultaneously solvable equations relate to a plurality of reconstructed superimposed images, one on each of a plurality of multi-sheet surfaces, and a plurality of z-positions of sheets of each multi-sheet surface intersecting each point in a region being imaged.

16. The method of claim 15 wherein said simultaneously solvable equations is solved using at least one of a least squares, a minimization of a sum of absolute values of residuals, a minimization of any weighted norm of residuals, a minimization of any weighted norm of residuals where said weights are derived from a model of data errors, structured Total Least Norms, Iteratively Reweighted Least Squares and Iteratively Reweighted Norm approaches, optimization methods including primal-dual methods, gradient methods, gradient projection methods, nonlinear reconstruction methods, with any type of regularization, penalty or constraints.

17. The method of claim 15, which uses said simultaneous equations incorporate the direction point spread functions in an axial direction to improve approximation with detected X-rays which were at least partially not on a rebinning surface.

18. The method of claim 14, wherein said method includes the steps of performing backprojection without filtering on multi-sheet surfaces;

axial deconvolution; and

subsequently filtering on each transaxial slice of a volume being imaged.

19. The method of claim 12 wherein the method of generating said three dimensional image is initiated after a threshold amount of detected X-ray data are obtained well before the data for the entire object has been acquired.

20. The method of claim 12 further comprising the step of correcting sinogram data on a rebinning surface using at least one of an optical flow technique or any Partial Differential Equation technique.