Imaging system for generating a substantially exact reconstruction of a region of interest

• US 7,394,923 B2
• Filed: 02/10/2005
• Issued: 07/01/2008
• Est. Priority Date: 02/10/2004
• Status: Active Grant

• Current Assignee: University of Chicago
• Original Assignee: University of Chicago
• Inventors: Zou, Yu, Pan, Xiaochuan M.
• Primary Examiner(s): Bali; Vikkram
• Assistant Examiner(s): Redding; Thomas M
• Application Number:
  US11/054,788
• Publication Number:
  US 20050249432A1
• Time in Patent Office: 1,237 Days
• Field of Search: None
• US Class Current: 382/131
• 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 6/037 Emission tomography
• CPC Class Codes: A61B 6/508 for non-human patients
• 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 11/006 Inverse problem, transformation from projection-space into object-space, e.g. transform methods, back-projection, algebraic methods
• CPC Class Codes: G06T 2211/416 Exact reconstruction
• CPC Class Codes: G06T 2211/421 Filtered back projection [FBP]

Abstract

A method and apparatus for reconstruction of a region of interest for an object is provided. The reconstruction of the object may be based on chords which may fill a part, all, or more than all of the region of interest. Using chords for reconstruction may allow for reducing data acquired and/or processing for reconstructing a substantially exact image of the ROI. Moreover, various methodologies may be used in reconstructing the image, such as backprojection-filtration, and modified filtration backprojection.

Claims

1. A method of imaging at least a part of a region of interest (ROI) comprising:

decomposing the at least a part of the ROI into chords; and

reconstructing the at least a part of the ROI based on the chords using data,

wherein an object support comprises a domain in space within which the object may be non-zero and outside of which is certainly zero;

wherein the ROI is a portion of and smaller than the object support;

wherein a trajectory of a source relative to the object defines a coordinate system; and

wherein the source illuminates the ROI during at least a part of the trajectory resulting in the data being acquired, the data comprising projections containing truncations along at least two axes of said coordinate system.

2. The method of claim 1, wherein the trajectory comprises a helical trajectory.

3. A computer-readable medium containing program code for:

imaging at least part of a region of interest (ROI);

decomposing the at least a part of the ROI into chords; and

reconstructing the at least a part of the ROI based on the chords using data,

wherein an object support comprises a domain in space within which the object may be non-zero and outside of which is certainly zero;

wherein the ROI is a portion of and smaller than the object support;

wherein a trajectory of a source relative to the object defines a coordinate system; and

wherein the source illuminates the ROI during at least a part of the trajectory resulting in the data being acquired, the data comprising projections containing truncations along at least two axes of said coordinate system.

4. The computer-readable medium of claim 3, wherein the trajectory comprises a helical trajectory.

5. A method of imaging at least a part of a region of interest (ROI), the ROI being a portion of and smaller than an object support comprising a domain in space within which the object may be non-zero and outside of which is certainly zero, the method comprising:

controlling at least one of a source and the object support so that the source and the object support move relative to one another in a trajectory that defines a rotation axis;

acquiring data at least partly when the source and the object support move relative to one another; and

generating a substantially exact reconstruction of the ROI based on the data, the data being less than that required to substantially exactly reconstruct an image of the entire object support,

wherein the data comprises projections, such projections containing truncations parallel and perpendicular to the rotation axis.

6. The method of claim 5, wherein the data that is used to generate a substantially exact reconstruction excludes data in at least a part of object support that is outside of the ROI.

7. The method of claim 6, wherein the data that is used to generate a substantially exact reconstruction completely excludes the data in the part of the object support that is outside of the ROI.

8. The method of claim 5, wherein the data is acquired using an imaging system;

and

wherein acquiring the data for imaging the ROI comprises selecting at least one parameter for the imaging system so that the data acquired by the imaging system is less than that required to substantially exactly reconstruct an image of the entire object support.

9. The method of claim 8,

wherein the at least one parameter comprises a parameter of the trajectory of the source relative to the object support.

10. The method of claim 8,

wherein the at least one parameter comprises an illumination parameter for the source.

11. The method of claim 10, wherein the source generates a beam with a beam size;

and

wherein the illumination parameter comprises the beam size.

12. The method of claim 11, further comprising modifying the beam size of the source in order to acquire the data that is less than that required to substantially exactly reconstruct an image of the entire object support.

13. The method of claim 12, wherein the trajectory of the source relative to the object support comprises a helical trajectory.

14. The method of claim 5, wherein generating a substantially exact reconstruction of the ROI comprises:

decomposing the ROI into chords; and

substantially exactly reconstructing the ROI based on the chords.

15. The method of claim 14, wherein the chords comprise PI-lines.

16. The method of claim 14, wherein the chords are defined by the trajectory of a source relative to the object support.

17. The method of claim 16, wherein generating a substantially exact reconstruction of the ROI comprises:

identifying a set of chords that connect pairs of points along the trajectory, wherein the set of chords fill a volume for the ROI;

calculating image densities on the chords from the acquired data; and

constructing a three-dimensional image based on the image densities.

18. The method of claim 5, wherein generating a substantially exact reconstruction of the ROI comprises:

backprojecting based on the acquired data to generate an intermediate density distribution; and

filtering the intermediate density distribution to create a substantially exact image of the ROI.

19. The method of claim 5, wherein generating a substantially exact reconstruction of the ROI comprises:

filtering the acquired data; and

backprojecting the filtered data to generate a density distribution.

20. The method of claim 5, wherein generating a substantially exact reconstruction of the ROI comprises rebinning the data.

21. The method of claim 5, wherein the ROI is 2-dimensional.

22. The method of claim 5, wherein the ROI is 3-dimensional.

23. The method of claim 5, wherein the imaging comprises computed tomography.

24. The method of claim 5, wherein the trajectory comprises a helical trajectory or a circular trajectory.

25. The method of claim 24, wherein the source comprises a beam angle;

and

wherein the trajectory, during which the source illuminates the ROI, covers an angular range less than a range of π

+the beam angle.

26. The method of claim 25, wherein the ROI comprises at least a portion of a breast.

27. The method of claim 25, wherein the ROI comprises at least a portion of an internal organ.

28. An apparatus for imaging at least a part of a region of interest (ROI), the ROI being a portion of and smaller than an object support comprising a domain in space within which the object may be non-zero and outside of which is certainly zero, the apparatus comprising:

a source for illuminating the ROI;

at least one motor to control at least one of the source or the object support in order to move the source relative to the object support in a trajectory that defines a rotation axis;

at least one sensor to acquire data at least partly when the source and the object support move relative to one another; and

a processor to generate a substantially exact reconstruction of the ROI based on the data, the data being less than that required to substantially exactly reconstruct an image of the entire object support,

wherein the data comprises projections, such projections containing truncations parallel and perpendicular to the rotation axis.

29. The apparatus of claim 28, wherein the data that is used to generate a substantially exact reconstruction excludes data in at least a part of object support that is outside of the ROI.

30. The apparatus of claim 29, wherein the data that is used to generate a substantially exact reconstruction completely excludes the data in the part of object support that is outside of the ROI.

31. The apparatus of claim 28,

wherein the processor selects at least one parameter for the apparatus so that the data acquired by the at least one sensor is less than that required to substantially exactly reconstruct an entire image of the object support.

32. The apparatus of claim 31,

wherein the at least one parameter comprises a parameter of the trajectory of the source relative to the object support.

33. The apparatus of claim 31,

wherein the at least one parameter comprises an illumination parameter for the source.

34. The apparatus of claim 33, wherein the source generates a beam with a beam size;

and

wherein the illumination parameter comprises the beam size.

35. The apparatus of claim 34, wherein the processor modifies the beam size of the source in order to acquire the data that is less than that required to substantially exactly reconstruct an image of the entire object support.

36. The apparatus of claim 35, wherein the trajectory of the source relative to the object support comprises a helical trajectory.

37. The apparatus of claim 28, wherein generating a substantially exact reconstruction of the ROI comprises:

decomposing the ROI into chords; and

substantially exactly reconstructing the ROI based on the chords.

38. The apparatus of claim 37, wherein the chords comprise PI-lines.

39. The apparatus of claim 37, wherein the chords are defined by a trajectory of a source relative to the object support.

40. The apparatus of claim 39, wherein generating a substantially exact reconstruction of the ROI comprises:

identifying a set of chords that connect pairs of points along the trajectory, wherein the set of chords fill a volume for the ROI;

calculating image densities on the chords from the acquired data; and

constructing a three-dimensional image based on the image densities.

41. The apparatus of claim 28, wherein generating a substantially exact reconstruction of the ROI comprises:

backprojecting based on the acquired data to generate an intermediate density distribution; and

filtering the intermediate density distribution to create a substantially exact image of the ROI.

42. The apparatus of claim 28, wherein generating a substantially exact reconstruction of the ROI comprises:

filtering the acquired data; and

backprojecting the filtered data to generate a density distribution.

43. The apparatus of claim 28, wherein generating a substantially exact reconstruction of the ROI comprises rebinning the data.

44. The apparatus of claim 28, wherein the ROI is 2-dimensional.

45. The apparatus of claim 28, wherein the ROI is 3-dimensional.

46. The apparatus of claim 28, wherein the imaging comprises computed tomography.

47. The apparatus of claim 28, wherein the trajectory comprises a helical trajectory or a circular trajectory.

48. The apparatus of claim 47, wherein the source comprises a beam angle;

and

wherein the trajectory, during which the source illuminates the ROI, covers an angular range less than a range of π

+the beam angle.

49. The apparatus of claim 48, wherein the ROI comprises at least a portion of a breast.

50. The apparatus of claim 48, wherein the ROI comprises at least a portion of an internal organ.