METHOD AND APPARATUS OF CONE BEAM CT DYNAMIC IMAGING

• US 20100158335A1
• Filed: 11/13/2009
• Published: 06/24/2010
• Est. Priority Date: 02/27/2006
• Status: Active Grant

• Current Assignee: University of Rochester
• Original Assignee: University of Rochester
• Inventors: NING, Ruola, YANG, Dong
• Granted Patent: US 8,976,925 B2
• Time in Patent Office: Days
• 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 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/0435 with means for imaging suspended breasts
• CPC Class Codes: A61B 6/502 for diagnosis of breast, i.e. mammography
• 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: Y10S 378/901 Computer tomography program or processor

Abstract

A cone-beam scanning system scans along a half circle. The reconstruction uses a weighting function which decreases for rows farther from the scan plane to take the redundancy of the projection data into account. Another embodiment uses a circle plus sparse helical scan geometry. Image data can be taken in real time.

Claims

1. A method for forming an image of an object, the method comprising:

(a) performing a cone-beam scan of the object in a scanning plane by using a cone-beam emitter and a detector to perform a half-circle scanning geometry so as to obtain projection data for a plurality of rows;

(b) weighting the projection data with a weighting factor to produce weighted projection data, wherein the weighting factor decreases as the rows become farther from the scanning plane; and

(c) forming the image from the weighted projection data.

2. The method of claim 1, wherein step (c) comprises filtering the weighted projection data.

3. The method of claim 1, wherein the weighting factor is a function of a weighting angle which is a function of the row and a scan inagle.

4. The method of claim 3, wherein the weighting angle is

5. The method of claim 4, wherein the weighting factor is

6. The method of claim 1, further comprising, between steps (b) and (c), adding to the weighted projection data a correction term representing information in Radon space which cannot be acquired through a circular scan.

7. The method of claim 1, wherein steps (a), (b) and (c) are performed in real time.

8. A method for forming an image of an object, the method comprising:

(a) performing a cone-beam scan of the object in a scanning plane by using a cone-beam emitter and a detector to perform a circle or partial circle plus spiral scanning geometry so as to obtain projection data, wherein the scanning geometry comprises a circle or partial circle scanning geometry and a spiral scanning geometry, and wherein the projection data comprise projection data taken only at discrete points along the spiral scanning geometry; and

(b) forming the image from the projection data.

9. The method of claim 8, wherein the object comprises a breast.

10. The method of claim 9, wherein the circle or partial circle scanning geometry is around the breast and the spiral scanning geometry is along the breast.

11. The method of claim 10, wherein step (b) comprises adding terms from the circle or partial circle scanning geometry and the spiral scanning geometry.

12. The method of claim 11, wherein step (b) further comprises adding a correction term representing information in Radon space which cannot be acquired through a circular scan.

13. A system for forming an image of an object, the system comprising:

a cone-beam emitter;

a detector;

a gantry for causing relative movement of the emitter and the detector for performing a cone-beam scan of the object in a scanning plane by using a cone-beam emitter and a detector to perform a half-circle scanning geometry so as to obtain projection data for a plurality of rows; and

a processor, receiving the projection data, for weighting the projection data with a weighting factor to produce weighted projection data, wherein the weighting factor decreases as the rows become farther from the scanning plane and forming the image from the weighted projection data.

14. The system of claim 13, wherein the processor filters the weighted projection data.

15. The system of claim 13, wherein the weighting factor is a function of a weighting angle which is a function of the row and a scan inagle.

16. The system of claim 15, wherein the weighting angle is

17. The system of claim 16, wherein the weighting factor is

18. The system of claim 13, wherein the processor adds to the weighted projection data a correction term representing information in Radon space which cannot be acquired through a circular scan.

19. The system of claim 13, wherein the emitter, detector, gantry and processor operate in real time.

20. A system for forming an image of an object, the system comprising:

a cone-beam emitter;

a detector;

a gantry for causing relative movement of the emitter and the detector for performing a cone-beam scan of the object in a scanning plane by using a cone-beam emitter and a detector to perform a circle or partial circle plus spiral scanning geometry so as to obtain projection data, wherein the scanning geometry comprises a circle or partial circle scanning geometry and a spiral scanning geometry, and wherein the projection data comprise projection data taken only at discrete points along the spiral scanning geometry; and

a processor, receiving the projection data, for forming the image from the projection data.

21. The system of claim 20, wherein the processor adds terms from the circle or partial circle scanning geometry and the spiral scanning geometry.

22. The system of claim 21, wherein the processor further adds a correction term representing information in Radon space which cannot be acquired through a circular scan.

23. The system of claim 20, wherein the gantry rotates around an axis of rotation for the circle or partial circle scanning geometry and both rotates around the axis of rotation and moves along the axis of rotation for the spiral scanning geometry.

24. A device for producing a cone beam CT image of an object, the device comprising:

a gantry frame;

at least one motor for moving the gantry frame to form a data acquisition geometry;

a source of cone-beam radiation attached to the gantry frame to move with the gantry frame;

a two-dimensional detector attached to the gantry frame to move with the gantry frame, the two-dimensional detector being disposed in a path of the radiation;

a support on which the patient rests while the projection images of the object are taken, the support supporting the object such that the object is disposed between the source of cone-beam radiation and the two-dimensional detector; and

at least one computer system to control scan of an object, perform reconstruction of the object and image analysis of images.

characterized in that;

the source of radiation is a cone beam source of radiation;

the images taken are cone beam CT projection of the object images;

the at least one motor moves the gantry frame so that a volume scan of the object can be taken by synchronously rotating the source and the detector around an axis passing through the object to form a data acquisition geometry for cone beam volume computed tomography, the volume scan resulting in image signals;

the three-dimensional cone beam CT image is formed from the image signals by performing a cone beam computed tomography reconstruction on the image signals to produce a three-dimensional attenuation coefficient distribution of the object and, the at least one motor comprises a motor for moving the source and the two-dimensional detector to define a data acquisition geometry.

25. The device of claim 24, further characterized in that the data acquisition geometry is a half scan that is defined as a 180°

plus cone angle circle scan.

26. The device of claim 24, further characterized in that the data acquisition geometry is a circle scan geometry

27. The device of claim 24, further characterized in that the data acquisition geometry is a spiral geometry.

28. The device of claim 24, further characterized in that the data acquisition geometry is a circle-plus-line geometry.

29. The device of claim 28, further characterized in that the circle-plus-line geometry comprises a single line.

30. The device of claim 28, further characterized in that the circle-plus-line geometry comprises a plurality of lines.

31. The device of claim 24, further characterized in that the data acquisition geometry is a 360°

scan with which a multiple sets of projection images can be generated from a multiple of half scan reconstructions.

32. The device of claim 24, further characterized in that the data acquisition geometry is a scan over N×

360°

, where N is a positive integer.

33. A device for producing a cone beam CT image of an object, the device comprising:

a gantry frame;

at least one motor for moving the gantry frame to form a data acquisition geometry;

a source of radiation attached to the gantry frame to move with the gantry frame;

a two-dimensional detector attached to the gantry frame to move with the gantry frame, the two-dimensional detector being disposed in a path of the radiation;

a support on which the object rests while the projection images of the object are taken, the support supporting the object such that the object is disposed between the source of radiation and the two-dimensional detector; and

at least one computer system to control scan of a breast, perform reconstruction of the breast and image analysis of images;

characterized in that;

the source of radiation is a cone beam source of radiation;

the images taken are cone beam CT projection images;

the at least one motor moves the gantry frame so that a volume scan of the object can be taken by synchronously rotating the source and the detector around an axis passing through the object to form a data acquisition geometry for cone beam volume computed tomography, the volume scan resulting in image signals;

the three-dimensional cone beam volume CT image is formed from the image signals by performing a cone beam volume computed tomography reconstruction on the image signals to produce a three-dimensional attenuation coefficient distribution of the breast;

the at least one motor moves the gantry frame so that the two-dimensional detector takes a volume scan of the object;

the device further comprises a slip ring on the gantry frame for providing the connection to the electrical power to the on-gantry components and the communication between the two-dimensional detector and the computer system; and

the at least one motor moves the gantry frame so that the two-dimensional detector takes a volume scan of the object.