Nutating slice CT image reconstruction apparatus and method

• US 5,802,134 A
• Filed: 04/09/1997
• Issued: 09/01/1998
• Est. Priority Date: 04/09/1997
• Status: Expired due to Term

• Current Assignee: Analogic Corporation
• Original Assignee: Analogic Corporation
• Inventors: Larson, Gregory L., Crawford, Carl R., Ruth, Christopher C.
• Primary Examiner(s): Porta, David P.
• Assistant Examiner(s): Bruce, David Vernon
• Application Number:
  US08/831,558
• Time in Patent Office: 510 Days
• Field of Search: 378/4, 378/15, 378/901, 250/363.02, 250/363.04, 250/363.1, 250/370.08, 250/370.09, 250/370.1
• 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: Y10S 378/901 Computer tomography program or processor

Abstract

A nutating slice CT image reconstruction apparatus and method generates a set of projection data using helical cone-beam scanning. The three-dimensional projection data is used to reconstruct a series of planar image slices. The slices are selected such that they define a tilt angle and a rotation angle with respect to the longitudinal axes of the object being scanned. Successive slices have equal tilt angles but changing rotation angles such that normal axes of successive slices define a nutation and precession about the longitudinal axis of the object. Projection data for the tilted slices are formed of selected one-dimensional fan-beam data. As such, the projection data can be applied to conventional two-dimensional reconstruction approaches to generate an image.

Claims

1. A method of reconstructing image data for a region having a longitudinal axis, said method comprising:

scanning the region with an array of detectors to generate scan data representative of the region;

defining a plurality of image data slices corresponding to a plurality of positions along the longitudinal axis of the region, successive image data slices being non-parallel with each other; and

using the scan data, generating image data for the plurality of image data slices.

2. The method of claim 1, wherein the region is scanned with a computed tomography (CT) device to generate the scan data.

3. The method of claim 1, wherein the region is scanned with a radiation source which directs radiation through the region onto the array of detectors.

4. The method of claim 3, wherein the radiation source is a cone-beam source.

5. The method of claim 1, wherein successive image data slices are nutated with respect to each other.

6. The method of claim 1, wherein the array of detectors is a two-dimensional array.

7. The method of claim 1, wherein the step of generating image data comprises applying a two-dimensional back projection computation to the scan data.

8. The method of claim 1, wherein the step of generating image data comprises applying a two-dimensional reconstruction computation to the scan data.

9. The method of claim 1, wherein the scan data is generated using a helical scan.

10. The method of claim 1, wherein the scan data is generated using a helical cone-beam scan.

11. The method of claim 10, wherein the step of generating image data comprises applying a two-dimensional back projection computation to the scan data.

12. The method of claim 10, wherein the step of generating image data comprises applying a two-dimensional reconstruction computation to the scan data.

13. The method of claim 1, further comprising rebinning the scan data to parallel-ray scan data.

14. The method of claim 1, further comprising providing overscan correction to the scan data.

15. A method of reconstructing image data for a computed tomography (CT) image of a region, said region having a longitudinal axis and a transverse axis orthogonal to the longitudinal axis, said method comprising:

scanning the region with a radiation source and an array of detectors to generate scan data representative of the region;

at each of a plurality of positions along the longitudinal axis of the region, defining image data slice, said image data slice defining a slice plane having a normal axis forming a tilt angle with the longitudinal axis of the region and a rotation angle with the transverse axis of the region such that the normal axes of successive image data slices have the same tilt angle and different rotation angles; and

using the scan data, generating image data for the plurality of image slices.

16. The method of claim 15, wherein the radiation source is a cone-beam source.

17. The method of claim 15, wherein the array of detectors is a two-dimensional array.

18. The method of claim 15, wherein the step of generating image data comprises applying a two-dimensional back projection computation to the scan data.

19. The method of claim 15, wherein the step of generating image data comprises applying a two-dimensional reconstruction computation to the scan data.

20. The method of claim 15, wherein the scan data is generated using a helical scan.

21. The method of claim 15, wherein the scan data is generated using a helical cone-beam scan.

22. The method of claim 21, wherein the step of computing image data comprises applying a two-dimensional back projection computation to the scan data.

23. The method of claim 21, wherein the step of generating image data comprises applying a two-dimensional reconstruction computation to the scan data.

24. The method of claim 15, further comprising rebinning the scan data to parallel-ray scan data.

25. The method of claim 15, further comprising providing overscan correction to the scan data.

26. The method of claim 15, further comprising, before scanning the region, performing a calibration scan with a tilted opaque disk to determine the tilt angle.

27. The method of claim 26, further comprising computing an area of a projection of the opaque disk on the array of detectors to minimize error in the reconstructed image data.

28. In a computed tomography (CT) system, a method of generating a reconstructed slice of image data comprising:

scanning a region with a radiation source and an array of detectors to generate a plurality of scan data, the region including an axis;

identifying a slice angle between the axis and a slice plane defined by the reconstructed slice such that error in the reconstructed slice image data is minimized; and

using the scan data, computing the image data for the reconstructed slice at the slice angle.

29. The method of claim 28, wherein the radiation source is a cone-beam source.

30. The method of claim 28, wherein the array of detectors is a two-dimensional array.

31. The method of claim 28, wherein the image data is computed from the scan data using a two-dimensional reconstruction computation.

32. The method of claim 28, wherein the scan data is generated using a helical scan.

33. The method of claim 28, wherein the scan data is generated using a helical cone-beam scan.

34. The method of claim 28, wherein identifying the slice angle comprises, before scanning the region, performing a calibration scan with a tilted opaque disk.

35. The method of claim 28, further comprising computing an area of a projection of the opaque disk on the array of detectors to minimize error in the reconstructed image data.

36. A system for generating image data for a region having a longitudinal axis, said system comprising:

an array of detectors for scanning the region to generate scan data representative of the region;

processing means for defining a plurality of image data slices at a plurality of positions along the longitudinal axis of the region such that successive image data slices are non-parallel with each other; and

generating means for computing image data for the plurality of image slices.

37. The system of claim 36, wherein the system is a computed tomography (CT) system.

38. The system of claim 36, further comprising a radiation source for directing radiation through the region and onto the array of detectors to scan the region.

39. The system of claim 38, wherein the radiation source is a cone-beam source.

40. The system of claim 36, wherein the array of detectors is a two-dimensional array.

41. The system of claim 36, wherein the generating means comprises two-dimensional back projection means for generating the image data.

42. The system of claim 36, wherein the generating means comprises two-dimensional reconstruction means for generating the image data.

43. The system of claim 36, further comprising two-dimensional back projection hardware for generating the image data.

44. The system of claim 36, wherein the array of detectors is adapted to perform a helical scan of the region.

45. The system of claim 36, wherein the array of detectors is adapted to perform a helical cone-beam scan of the region.

46. The system of claim 36, further comprising means for rebinning the scan data to parallel-ray scan data.

47. The system of claim 36, further comprising means for providing overscan correction to the scan data.

48. The system of claim 36, further comprising means for performing a calibration scan with a titled opaque disk before scanning the region.

49. The system of claim 48, further comprising means for computing an area of a projection of the opaque disk on the array of detectors to minimize error in the reconstructed image data.