Parallel processing architecture for computed tomography scanning system using non-parallel slices

• US 5,887,047 A
• Filed: 10/10/1997
• Issued: 03/23/1999
• Est. Priority Date: 04/09/1997
• Status: Expired due to Term

• Current Assignee: Analogic Corporation
• Original Assignee: Analogic Corporation
• Inventors: Greenberg, Alexander I., Bailey, Eric M., Crawford, Carl R., Ruth, Christopher C.
• Primary Examiner(s): Porta, David P.
• Assistant Examiner(s): Bruce, David Vernon
• Application Number:
  US08/948,697
• Time in Patent Office: 529 Days
• Field of Search: 378/4, 378/15, 378/901, 382/131
• 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. The projection data can also be used to generate two-dimensional projection images at one or more stationary projection angles through an object being scanned. The nutation or tilt of image volume elements can be compensated for to provide a more accurate image and more accurate target assessment such as accurate total mass determination. A parallel processing architecture can be used to generate and process the nutated slices with improved efficiency.

Claims

1. A method of processing computed tomography scan data for a region having a longitudinal axis, said method comprising:

scanning the region with a radiation source and an array of detectors to generate the scan data for the region, said scanning comprising rotating at least the radiation source about the longitudinal axis through a plurality of view angles while the radiation source emits radiation toward the array of detectors, the scan data comprising a plurality of sets of projection data acquired respectively at the plurality of view angles; and

generating slice data for a plurality of image data slices of the region from a plurality of the sets of projection data, each set of projection data comprising a plurality of projections used in generating a respective plurality of the image data slices and each image data slice being generated from a projection from each of a plurality of sets of projection data, said generating slice data comprising, for each image data slice;

associating a data storage element with the image data slice,

storing in the data storage element the projections to be used in generating the slice data for the image data slice, and

processing the stored projections to generate the slice data.

2. The method of claim 1 further comprising filtering the projections stored in the data storage elements to generate the image data slices for the region.

3. The method of claim 1 further comprising backprojecting the projections stored in the data storage elements to generate the image data slices for the region.

4. The method of claim 1 further comprising providing a processor for generating the plurality of projections from each set of projection data.

5. The method of claim 1 further comprising transferring projections for an image data slice to be generated from the processor to the data storage element associated with the image data slice to be generated.

6. The method of claim 1 further comprising providing a plurality of processors for generating the plurality of projections from each set of projection data.

7. The method of claim 1 further comprising associating each image data slice to be generated with one of the plurality of processors such that the one of the plurality of processors associated with an image data slice generates the projections for the image data slice.

8. The method of claim 7 further comprising demultiplexing the scan data acquired by the array of detectors to the plurality of processors.

9. The method of claim 7 further comprising demultiplexing the plurality of processors to the data storage elements.

10. The method of claim 7 wherein the projections are fan-beam projections.

11. The method of claim 10 wherein one of the plurality of processors is used to rebin the fan-beam projections to parallel beam projections.

12. The method of claim 10 wherein one of the plurality of processors is used to rebin the fan-beam projections for a first image data slice to parallel beam projections while another of the plurality of processors generates fan-beam projections for another image data slice from a set of projection data.

13. The method of claim 1 wherein the data storage elements are memories.

14. The method of claim 1 wherein the image data slices are non-parallel with each other.

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

16. The method of claim 1 wherein the image data slices are tilted with respect to the longitudinal axis.

17. The method of claim 1 wherein scanning the region further comprises translating the radiation source and the array of detectors along the longitudinal axis of the region while rotating at least the radiation source about the longitudinal axis of the region.

18. The method of claim 1 wherein the radiation source is a cone-beam source.

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

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

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

22. The method of claim 1 wherein the projections are fan-beam projections.

23. The method of claim 22 further comprising rebinning the fan-beam projections to parallel beam projections.

24. An apparatus for processing computed tomography scan data for a region having a longitudinal axis, said apparatus comprising:

a radiation source and an array of detectors for scanning the region to generate the scan data for the region, at least the radiation source being rotated about the longitudinal axis through a plurality of view angles while the radiation source emits radiation toward the array of detectors, the scan data comprising a plurality of sets of projection data acquired respectively at the plurality of view angles;

a processor for receiving the scan data and generating from each set of projection data a plurality of projections used in generating a respective plurality of image data slices such that each image data slice is generated from a projection from each of a plurality of sets of projection data; and

a data storage element associated with each image data slice, each data storage element storing projections used in generating the respective associated image data slice, the processor processing the stored projections from each data storage element to generate slice data for the image data slice associated with the data storage element.

25. The apparatus of claim 24 further comprising a filtering subsystem for filtering the projections stored in the data storage elements.

26. The apparatus of claim 24 further comprising a backprojection subsystem for backprojecting the projections stored in the data storage elements.

27. The apparatus of claim 24 further comprising a multiplexer for transferring the projections from the processor to the data storage elements.

28. The apparatus of claim 24 further comprising a plurality of processors for generating the plurality of projections from each set of projection.

29. The apparatus of claim 28 wherein each image data slice to be generated is associated with one of the plurality of processors such that the one of the plurality of processors associated with an image data slice generates the projections for the image data slice.

30. The apparatus of claim 28 further comprising a demultiplexor for transferring the scan data acquired by the array of detectors to the plurality of processors.

31. The apparatus of claim 28 further comprising a demultiplexor for transferring the projections from the plurality of processors to the data storage elements.

32. The apparatus of claim 28 wherein the projections are fan-beam projections.

33. The apparatus of claim 32 wherein one of the plurality of processors is used to rebin the fan-beam projections to parallel beam projections.

34. The apparatus of claim 32 wherein one of the plurality of processors is used to rebin the fan-beam projections for a first image data slice to parallel beam projections while another of the plurality of processors generates fan-beam projections for another image data slice from a set of projection data.

35. The apparatus of claim 24 wherein the data storage elements are memories.

36. The apparatus of claim 24 wherein the image data slices are non-parallel with each other.

37. The apparatus of claim 24 wherein successive image data slices are nutated with respect to each other.

38. The apparatus of claim 24 wherein the image data slices are tilted with respect to the longitudinal axis.

39. The apparatus of claim 24 further comprising means for translating the radiation source and the array of detectors along the longitudinal axis of the region while the radiation source and the array of detectors are rotated about the longitudinal axis of the region.

40. The apparatus of claim 24 wherein the radiation source is a cone-beam source.

41. The apparatus of claim 24 wherein the array of detectors is a two-dimensional array.

42. The apparatus of claim 24 wherein the array of detectors is adapted to perform a helical scan of the region.

43. The apparatus of claim 24 wherein the array of detectors is adapted to perform a helical cone-beam scan of the region.

44. The method of claim 24 wherein the projections are fan-beam projections.

45. The method of claim 44 wherein the fan-beam projections are rebinned to parallel beam projections.