Dynamic alignment of sparse photon counting detectors

1. An apparatus for controlling movement of a plurality of fixed detectors arranged in a computed tomography (CT) system that includes a rotating X-ray source, the apparatus comprising:

the plurality of fixed detectors, which are arranged on a ring that is stationary with respect to the X-ray source; and

a controller configured to

obtain a view angle of the X-ray source as the X-ray source rotates about an object,

select a detector of the plurality of fixed detectors that is within a scan field-of-view of the X-ray source at the obtained view angle,

determine a tilt angle for the detector that is within the scan field-of-view of the X-ray source at the obtained view angle so that an outer face of the detector directly faces the X-ray source, and

cause the detector to be moved to the determined tilt angle in a scan plane.

2. The apparatus of claim 1 , further comprising:

a motor configured to move the detector to the determined tilt angle.

3. The apparatus of claim 1 , wherein the detector is mounted on a shaft that is coupled to the motor.

4. The apparatus of claim 1 , wherein the detector is connected to a plurality of neighboring detectors via a link, and when the motor moves the detector to the determined tilt angle, the neighboring detectors are moved in a corresponding manner.

5. The apparatus of claim 1 , wherein the controller is further configured to determine, for the obtained view angle, which detectors of the plurality of detectors are within the scan field-of-view, and to determine a respective tilt angle for each of the plurality of detectors within the scan field-of-view.

6. The apparatus of claim 1 , wherein

the plurality of detectors are photon-counting detectors arranged on the ring in the CT system surrounding the X-ray source, and

the controller is configured to determine the tilt angle by determining a local source angle of the X-ray source, the local source angle of the X-ray source being determined based on the view angle of the X-ray source, which is an angle between a central ray in the scan field-of-view and an x-axis at a center of the ring, and an angle between a direction the outer face of the detector is facing and the x-axis.

7. The apparatus of claim 6 , wherein

the controller is configured to determine the local source angle of the X-ray source as

φ( t )=λ s ( t )−λ D ( k )−π,

where φ(t) is the local source angle of the X-ray source, λs(t) is the view angle of the X-ray source, and λ D (k) is the angle between the direction the outer face of the detector is facing and the x-axis.

8. The apparatus of claim 7 , wherein

the controller is configured to determine the tilt angle using

γ( t )=tan −1 (( Rs sin φ( t ))/( R D +R S cos φ( t ))),

where γ(t) is the tilt angle, Rs is a radius of an X-ray source ring on which the X-ray source is arranged, and R D is a radius of the ring on which the plurality of detectors are arranged.

9. A method for controlling movement of a plurality of fixed detectors arranged in a computed tomography (CT) system that includes a rotating X-ray source, the method comprising:

obtaining a view angle of the X-ray source as the X-ray source rotates about an object;

selecting a detector of the plurality of fixed detectors, which are arranged on a ring that is stationary with respect to the X-ray source that is within a scan field-of-view of the X-ray source at the obtained view angle;

determining a tilt angle for the detector that is within the scan field-of-view of the X-ray source at the obtained view angle so that an outer face of the detector directly faces the X-ray source; and

causing the detector to be moved to the determined tilt angle in a scan plane.

10. The method of claim 9 , further comprising:

moving a plurality of neighboring detectors of the detector in a corresponding manner to the detector, when moving the detector to the determined tilt angle, the detector being connected to the plurality of neighboring detectors via a link.

11. The apparatus of claim 9 , further comprising:

determining, for the obtained view angle, which detectors of the plurality of detectors are within the scan field-of-view; and

determining a respective tilt angle for each of the plurality of detectors within the scan field-of-view.

12. The method of claim 9 , wherein

the plurality of detectors are photon-counting detectors arranged on a ring in the CT system surrounding the X-ray source, and

the determining determines the tilt angle by determining a local source angle of the X-ray source, the local source angle of the X-ray source being determined based on the view angle of the X-ray source, which is an angle between a central ray in the scan field-of-view and an x-axis at a center of the ring, and an angle between a direction the outer face of the detector is facing and the x-axis.

13. The method of claim 12 , wherein

the determining determines the local source angle of the X-ray source as

φ( t )=λ s ( t )−λ D ( k )−π,

where φ(t) is the local source angle of the X-ray source, λs(t) is the view angle of the X-ray source, and λ D (k) is the angle between the direction the outer face of the detector is facing and the x-axis.

14. The method of claim 13 , wherein

the determining determines the tilt angle using

γ( t )=tan −1 (( Rs sin φ( t ))/( R D +R S cos φ( t ))),

where γ(t) is the tilt angle, Rs is a radius of an X-ray source ring on which the X-ray source is arranged, and R D is a radius of the ring on which the plurality of detectors are arranged.

15. The apparatus of claim 1 , wherein the controller determines the tilt angle based on a position of the X-ray source in the scan plane.

16. The method of claim 9 , wherein the determining determines the tilt angle based on a position of the X-ray source in the scan plane.