CT image reconstruction through employment of function that describes interpreted movement of source around particular point of object

• US 7,376,213 B1
• Filed: 02/23/2006
• Issued: 05/20/2008
• Est. Priority Date: 02/23/2006
• Status: Expired due to Fees

• Current Assignee: General Electric Company, University of Iowa Research Foundation
• Original Assignee: General Electric Company, University of Iowa Research Foundation
• Inventors: Hsieh, Jiang, Wang, Ge, Wei, Yuchuan
• Primary Examiner(s): Thomas; Courtney
• Assistant Examiner(s): Taningco; Alexander H
• Application Number:
  US11/276,301
• Time in Patent Office: 817 Days
• Field of Search: 378/4, 378/8, 378/38, 378/39, 378/901
• 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 6/032 Transmission computed tomography [CT]
• CPC Class Codes: G01T 1/2985 In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis); using external radiation sources A61B6/02
• 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 2211/412 Dynamic

Abstract

A CT system in an example comprises an x-ray source, a detector, a data acquisition system (DAS), and a computer. The x-ray source emits a beam of x-rays toward an object to be imaged. The detector receives x-rays emitted by the x-ray source. The DAS is operably connected to the detector. The computer is operably connected to the DAS. The computer is programmed to reconstruct a CT image of the object to comprise a plurality of CT images, of a respective plurality of points of the object, through employment of a function that describes how many times a trajectory curve, of an interpretation of relative movement between the x-ray source and the object as that of the x-ray source, goes around each of the plurality of points of the object.

Claims

1. A CT system, comprising:

an x-ray source that emits a beam of x-rays toward an object to be imaged;

a detector that receives x-rays emitted by the x-ray source;

a data acquisition system (DAS) operably connected to the detector; and

a computer operably connected to the DAS and programmed to;

reconstruct a CT image of the object to comprise a plurality of CT images, of a respective plurality of points of the object, through employment of a function that describes how many times a trajectory curve, of an interpretation of relative movement between the x-ray source and the object as that of the x-ray source, goes around each of the plurality of points of the object.

2. The CT system of claim 1, wherein the computer operably connected to the DAS is programmed to:

prepare the interpretation of the relative movement between the x-ray source and the object as that of the x-ray source as the trajectory curve;

prepare the trajectory curve as interpreted movement of the x-ray source relative to a coordinate system fixed with respect to the object; and

reconstruct the CT image of the object through employment of the function, wherein the function comprises a turn function that describes how many times the trajectory curve loops around a particular point, of the plurality points of the object, in a predefined direction.

3. The CT system of claim 1, wherein the computer operably connected to the DAS is programmed to:

prepare the interpretation of the relative movement between the x-ray source and the object as that of the x-ray source as the trajectory curve;

prepare the trajectory curve as interpreted movement of the x-ray source relative to a coordinate system fixed with respect to the object; and

reconstruct the CT image of the object through employment of the function, wherein the function looks outward from a particular point, of the plurality points of the object, and counts in the trajectory curve;

a number of turns in a predefined direction about the particular point of the object; and

a number of turns opposite to the predefined direction about the particular point of the object.

4. The CT system of claim 1, wherein the computer operably connected to the DAS is programmed to:

prepare the interpretation of the relative movement between the x-ray source and the object as that of the x-ray source as the trajectory curve;

prepare the trajectory curve as interpreted movement of the x-ray source relative to a coordinate system fixed with respect to the object; and

reconstruct the CT image of the object through employment of the function, wherein the function yields a net number of times that the trajectory curve of the x-ray source goes around a particular point, of the plurality points of the object, in a predefined direction.

5. The CT system of claim 4, wherein the computer operably connected to the DAS is programmed to reconstruct the CT image of the object through employment of the function, wherein the function treats:

a component value of the trajectory curve in the predefined direction; and

a component value of the trajectory curve opposite to the predefined direction;

to comprise a tendency to cancel each other out.

6. The CT system of claim 1, wherein the computer operably connected to the DAS is programmed to:

prepare the interpretation of the relative movement between the x-ray source and the object as that of the x-ray source as the trajectory curve;

prepare the trajectory curve as interpreted movement of the x-ray source relative to a coordinate system fixed with respect to the object; and

reconstruct the CT image of the object through employment of the function, wherein the function identifies a point of the object that is to be omitted from the plurality of CT images of the respective plurality of points of the object because of a condition of the point of the object as tested by the function.

7. The CT system of claim 1, wherein the computer operably connected to the DAS is programmed to:

prepare the interpretation of the relative movement between the x-ray source and the object as that of the x-ray source as the trajectory curve;

prepare the trajectory curve as interpreted movement of the x-ray source relative to a coordinate system fixed with respect to the object; and

reconstruct the CT image of the object through employment of the function, wherein the function provides respective distinct values for the plurality of points of the object in a reconstruction plane that comprises the coordinate system fixed with respect to the object.

8. The CT system of claim 1, wherein the computer operably connected to the DAS is programmed to:

prepare the interpretation of the relative movement between the x-ray source and the object as that of the x-ray source as the trajectory curve;

prepare the trajectory curve as interpreted movement of the x-ray source relative to a coordinate system fixed with respect to the object; and

reconstruct the CT image of the object through employment of the function, wherein the function provides a correspondence between values returned by the function and the plurality of points on the object in a reconstruction plane that comprises the coordinate system fixed with respect to the object.

9. The CT system of claim 1, wherein the object comprises one or more parts of a large object, wherein the computer operably connected to the DAS is programmed to:

move a radioactive source along a complicated trajectory in a spare space of a large object for probing the one or more parts of the large object;

employ one or more virtual paths to close an open source locus to create a virtual locus as the trajectory curve; and

obtain projection data at the virtual locus from measured data via interpolation.

10. A method, comprising the steps of:

interpreting relative movement between a high frequency electromagnetic energy projection source and a target object as interpreted movement of the high frequency electromagnetic energy projection source relative to a coordinate system fixed with respect to the target object for an interpretation of CT image data of the target object; and

reconstructing a CT image of the target object through employment of a function that describes how many times the interpreted movement of the high frequency electromagnetic energy projection source goes around a particular point of the target object.

11. The method of claim 10, wherein the step of interpreting the relative movement between the high frequency electromagnetic energy projection source and the target object as the interpreted movement of the high frequency electromagnetic energy projection source relative to the coordinate system fixed with respect to the target object for the interpretation of the CT image data of the target object comprises the step of:

interpreting actual movement of the target object as at least part of the interpreted movement of the high frequency electromagnetic energy projection source relative to the coordinate system fixed with respect to the target object for the interpretation of the CT image data of the target object.

12. The method of claim 10, wherein the step of interpreting the relative movement between the high frequency electromagnetic energy projection source and the target object as the interpreted movement of the high frequency electromagnetic energy projection source relative to the coordinate system fixed with respect to the target object for the interpretation of the CT image data of the target object comprises the step of:

interpreting actual movement of the high frequency electromagnetic energy projection source as at least part of the interpreted movement of the high frequency electromagnetic energy projection source relative to the coordinate system fixed with respect to the target object for the interpretation of the CT image data of the target object.

13. The method of claim 10, wherein the step of interpreting the relative movement between the high frequency electromagnetic energy projection source and the target object as the interpreted movement of the high frequency electromagnetic energy projection source relative to the coordinate system fixed with respect to the target object for the interpretation of the CT image data of the target object comprises the step of:

interpreting complex movement of the target object as at least part of the interpreted movement of the high frequency electromagnetic energy projection source relative to the coordinate system fixed with respect to the target object for the interpretation of the CT image data of the target object.

14. The method of claim 10, wherein the step of interpreting the relative movement between the high frequency electromagnetic energy projection source and the target object as the interpreted movement of the high frequency electromagnetic energy projection source relative to the coordinate system fixed with respect to the target object for the interpretation of the CT image data of the target object comprises the step of:

interpreting complex movement of the high frequency electromagnetic energy projection source as at least part of the interpreted movement of the high frequency electromagnetic energy projection source relative to the coordinate system fixed with respect to the target object for the interpretation of the CT image data of the target object.

15. The method of claim 10, wherein the step of reconstructing the CT image of the target object through employment of the function that describes how many times the interpreted movement of the high frequency electromagnetic energy projection source goes around the particular point of the target object comprises the step of:

employing the interpreted movement of the high frequency electromagnetic energy projection source as non-circular movement of the high frequency electromagnetic energy projection source relative to an origin of the coordinate system fixed with respect to the target object.

16. The method of claim 10, wherein the step of reconstructing the CT image of the target object through employment of the function that describes how many times the interpreted movement of the high frequency electromagnetic energy projection source goes around the particular point of the target object comprises the step of:

employing the interpreted movement of the high frequency electromagnetic energy projection source as a source trajectory with changes in radius and direction of the high frequency electromagnetic energy projection source relative to an origin of the coordinate system fixed with respect to the target object.

17. The method of claim 10, wherein the step of reconstructing the CT image of the target object through employment of the function that describes how many times the interpreted movement of the high frequency electromagnetic energy projection source goes around the particular point of the target object comprises the steps of:

employing the interpreted movement of the high frequency electromagnetic energy projection source as a source trajectory that in some places loops around and in some places goes back and forth in the coordinate system fixed with respect to the target object;

allowing the source trajectory to not necessarily be differentiable; and

operating without an assumption the function should be zero outside a field of view of the target object.

18. A method for CT imaging with a complicated scanning trajectory, the method comprising the steps of:

filtering projection data by Ram-Lak filter or a variant of the Ram-Lak filter, wherein the projection data correspond to the complicated scanning trajectory;

multiplying the projection data by increments relative to a view angle and focus distance; and

backprojecting the projection data to form an image through employment of a turn number function.

19. The method of claim 18, further comprising the step of:

handling the complicated scanning trajectory with small local loops and/or zigzags.

20. The method of claim 18, wherein the step of filtering projection data by the Ram-Lak filter or the variant of the Ram-Lak filter comprises the step of:

interpreting a known real motion of an object as the complicated scanning trajectory in a coordinate system oriented with respect to the object.