Methods and apparatus for scanning an object in a computed tomography system

• US 5,864,598 A
• Filed: 04/21/1997
• Issued: 01/26/1999
• Est. Priority Date: 04/21/1997
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Hsieh, Jiang, Fox, Stanley H.
• Primary Examiner(s): Porta, David P.
• Assistant Examiner(s): Bruce, David Vernon
• Application Number:
  US08/837,545
• Time in Patent Office: 645 Days
• Field of Search: 378/4, 378/15, 378/19, 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: H04N 23/30 for generating image signals from X-rays
• CPC Class Codes: H04N 5/32 Transforming X-rays cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

The present invention, in one form, is a system for generating a high resolution image of an object from projection data acquired during a computed tomography scan. The system includes a gantry having an x-ray source which rotates around the object. The x-ray source emits an x-ray beam which is collimated with a collimator having a collimator aperture to define an x-ray beam width, or slice thickness. The projection data is reconstructed to generate image data for adjacent image slices. A deconvolution algorithm is applied to the image data to generate a deconvolved image having a finer, i.e., smaller, resolution than the collimator aperture.

Claims

1. A method for generating image data of an object scanned by a computed tomography system, the computed tomography system including a gantry having an x-ray source which rotates around the object, said method comprising the steps of:

obtaining projection data for at least two adjacent image slices;

processing the obtained projection data to generate image data; and

deconvolving the image data in a z-direction.

2. A method in accordance with claim 1 wherein obtaining projection data comprises the step of scanning the object with a helical scan.

3. A method in accordance with claim 2 wherein scanning the object comprises the step of performing a helical scan with a 0.5β

;

α

helical pitch, where α

is a collimator aperture size and β

is a slice thickness.

4. A method in accordance with claim 1 wherein deconvolving the image data comprises using a kernel whose size is at least 2.

5. A method in accordance with claim 1 wherein obtaining projection data comprises the step of scanning the object with an axial scan.

6. A method in accordance with claim 5 wherein the projection data obtained for one of the image slices at least partially overlaps the projection data obtained for another of the image slices.

7. A method in accordance with claim 1 wherein deconvolving the image data comprises the step of modifying a reconstruction kernel to improve x-y resolution.

8. A system for generating image data of an object, said system comprising a gantry having an x-ray source which rotates around the object, said system configured to:

obtain projection data for at least two image slices;

process the obtained projection data to generate image data; and

deconvolve the image data in a z-direction.

9. A system in accordance with claim 8 further comprising a kernel whose size is at least 2.

10. A system in accordance with claim 8 wherein to obtain projection data, said system is configured to scan the object with an axial scan.

11. A system in accordance with claim 8 wherein to obtain projection data, said system is configured to scan the object with a helical scan.

12. A system in accordance with claim 11 wherein said system is further configured to perform a helical scan with a 0.5β

;

α

helical pitch, where α

is a collimator aperture size and β

is a slice thickness.

13. A method for generating data of an object scanned by a computed tomography system, the computed tomography system including a gantry having an x-ray source which rotates around the object, said method comprising the steps of:

obtaining projection data for at least two adjacent slices;

deconvolving the projection data in a projection space, and processing the deconvolved projection data to generate image data to produce an image having a slice thickness less than the slice thickness of the projection data adjacent slices.

14. A method in accordance with claim 13 wherein obtaining projection data comprises the step of scanning the object with a helical scan.

15. A method in accordance with claim 13 wherein scanning the object comprises the step of performing a helical scan with a 0.5β

;

α

helical pitch, where α

is a collimator aperture size and β

is a slice thickness.

16. A method in accordance with claim 13 wherein deconvolving the projection data comprises using a kernel whose size is at least 2.

17. A method in accordance with claim 13 wherein obtaining projection data comprises the step of scanning the object with an axial scan.

18. A system for generating image data of an object, said system comprising a gantry having an x-ray source which rotates around the object, said system configured to:

obtain projection data for at least two adjacent slices;

deconvolve the projection data in a projection space; and

process the deconvolved projection data to generate image data to produce an image having a slice thickness less than the slice thickness of the projection data adjacent slices.

19. A system in accordance with claim 18 wherein to obtain projection data, said system is configured to perform an axial scan of the object.

20. A system in accordance with claim 18 wherein to obtain projection data, said system is configured to scan the object with a helical scan.