FOCAL SPOT POSITION DETERMINER

• US 20110176663A1
• Filed: 01/21/2010
• Published: 07/21/2011
• Est. Priority Date: 01/21/2010
• Status: Active Grant

• Current Assignee: Analogic Corporation
• Original Assignee: Analogic Corporation
• Inventors: Shaughnessy, Charles
• Granted Patent: US 8,262,288 B2
• Time in Patent Office: Days
• US Class Current: 378/154
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/08 Auxiliary means for directing the radiation beam to a particular spot, e.g. using light beams
• CPC Class Codes: A61B 6/4021 involving movement of the focal spot
• CPC Class Codes: A61B 6/4291 the detector being combined with a grid or grating
• CPC Class Codes: A61B 6/585 Calibration of detector units

Abstract

One or more systems and/or techniques are disclosed herein for determining the orientation of a focal spot of a radiation source based upon shadows that are imposed on channels of a detector array from an anti-scatter grid. The anti-scatter grid is comprised of one or more anti-scatter plates that are focused on a point other than an intended focal spot of the radiation source. Such anti-scatters plates cast shadows on the detector array (even when the focal spot is located at the intended focal spot). By measuring changes in the signals generated by channels of the detector array that detect the shadows, it may be determined how the orientation of the focal spot has changed throughout an examination or between a calibration scan and an examination scan, for example.

Claims

1. A radiography scanning apparatus, comprising:

a radiation source configured to emit radiation;

a detector array configured to detect the emitted radiation; and

an anti-scatter grid comprised of a plurality of anti-scatter plates, wherein a first set of the anti-scatter plates are focused on a point other than an intended focal spot of the radiation source, and wherein a second set of anti-scatter plates are focused on the intended focal spot, the second set different than the first set.

2. The apparatus of claim 1, wherein the anti-scatter grid is a two-dimensional (2-d) anti-scatter grid and the first set of anti-scatter plates are z-axis anti-scatter plates.

3. The apparatus of claim 2, wherein the 2-d anti-scatter grid comprises a plurality of anti-scatter modules, wherein at least one anti-scatter module is tilted in the z-dimension relative to remaining anti-scatter modules of the 2-d anti-scatter grid.

4. The apparatus of claim 3, wherein at least a first and second anti-scatter module are tilted in the z-dimension relative to remaining anti-scatter modules of the 2-d anti-scatter grid, the first anti-scatter module titled in a first direction and the second anti-scatter module tilted in a second direction, the second direction different than the first direction.

5. The apparatus of claim 2, wherein a first anti-scatter plate of the first set of anti-scatter plates is positioned in a center row parallel to an x-axis and is angled at an angle other than ninety degrees in the z-dimension relative to an underlying detector surface of the detector array.

6. The apparatus of claim 5, wherein the anti-scatter plates that comprise the first set of anti-scatter plates are substantially parallel.

7. The apparatus of claim 1, wherein the detector array is comprised of at least one calibration channel, the calibration channel in close spatial proximity to a first anti-scatter plate of the first set of anti-scatter plates and configured to generate signals indicative of an orientation of a focal spot.

8. The apparatus of claim 7, comprising a correction component configured to identify a change in the orientation of the focal spot between a calibration scan and an examination scan based upon the signals generated by the calibration channel.

9. The apparatus of claim 1, wherein the detector array comprises at least one calibration channel and at least one imaging channel, wherein the calibration channel is in close spatial proximity to an anti-scatter plate of the first set of anti-scatter plates and the imaging channel is in close spatial proximity to an anti-scatter plate of the second set of anti-scatter plates.

10. The apparatus of claim 9, comprising:

a correction component configured to correct at least one of a signal generated by the imaging channel during an examination scan and projection data yielded from the signal generated by the imaging channel during the examination scan based upon a signal generated by the calibration channel during the examination scan.

11. The apparatus of claim 1, wherein a third set of anti-scatter plates are focused on a second point other than the intended focal spot, the third set different than the first set and the second set.

12. A method, comprising:

receiving a signal that was generated by a calibration channel of a detector array during a calibration scan;

receiving a signal that was generated by the calibration channel of the detector array during an examination scan;

determining an orientation of a focal spot during the examination scan based on the signal that was generated by the calibration channel during the calibration scan and the signal that was generated by the calibration channel during the examination scan;

receiving a signal that was generated by an imaging channel of the detector array during the examination; and

correcting at least one of the signal that was generated by the imaging channel during the examination and projection data yielded from the signal that was generated by the imaging channel during the examination, the correction based upon the determined orientation of the focal spot during the examination.

13. The method of claim 12, comprising:

detecting a first shadow cast on the calibration channel during the calibration scan, the first shadow cast from an anti-scatter plate that is focused on a point other than an intended focal spot;

generating a first signal at the calibration channel in response to the detected first shadow;

detecting a second shadow cast on the calibration channel during the examination scan, the second shadow cast from the anti-scatter plate that is focused on a point other than the intended focal spot; and

generating a second signal at the calibration channel in response to the detected second shadow.

15. The method of claim 12, comprising, aligning a first set of anti-scatter plates on a first point other than an intended focal spot of the radiation source.

16. The method of claim 15, comprising aligning a second set of anti-scatter plates on a second point other than the intended focal spot of the radiation source, wherein the second point and first point are substantially spaced an equal distance away from the intended focal spot, wherein the first point, the second point, and the intended focal spot lay on a z-axis, the intended focal spot laying between the first point and the second point.

17. The method of claim 12, comprising identifying one or more changes in the signal received from the calibration channel during the examination relative to the signal received from the calibration channel during the calibration.

18. The method of claim 17, wherein the orientation of the focal spot is determined based upon the identified one or more changes.

14. The method of 12, wherein determining comprises comparing the signal generated by the calibration channel during the calibration scan with the signal generated by the calibration channel during the examination scan.

19. A radiography scanning apparatus, comprising:

a radiation source configured to emit radiation;

an anti-scatter grid comprised of at least first and second sets of anti-scatter plates, the first set comprising anti-scatter plates that are focused on a point other than an intended focal spot of the radiation source and the second set comprising anti-scatter plates that are focused on the intended focal spot of the radiation source;

a detector array configured to detect the emitted radiation, the detector array comprising calibration channels and imaging channels, respective calibration channels positioned in close spatial proximity to an anti-scatter plate that is focused on the point other than the intended focal spot of the radiation source and respective imaging channels positioned in close spatial proximity to an anti-scatter plate that is focused on the intended focal spot of the radiation source, the calibration channels respectively configured to generate signals indicative of an orientation of a focal spot; and

a correction component configured to identify a change in the orientation of the focal spot between a calibration scan and an examination scan based upon the signals generated by the calibration channels.

20. The apparatus of claim 19, wherein the anti-scatter grid is a two-dimensional (2-d) anti-scatter grid and the first set of anti-scatter plates are z-axis anti-scatter plates.