Registration of 4

1. A method for determining, for a fourth-generation computed tomography (CT) scanner that includes a third-generation X-ray source and detector system and a plurality fixed, sparse photon-counting detectors (PCDs), a position of each PCD of the plurality of PCDs, the method comprising:

obtaining, for a given PCD of the plurality of PCDs, sinogram data from a reference scan of a plurality of line attenuators arranged at fixed, known positions within the CT scanner;

determining, by analyzing the sinogram data, a set of view angles of the X-ray source for which the sinogram data exhibits a decrease in count value, indicating a shadow cast by one of the line attenuators;

generating, for each view angle in the set of view angles, a line connecting a position of the X-ray source at the view angle, and a position of a line attenuator, of the plurality of line attenuators, that is closest to the position of the X-ray source at the view angle, to generate a set of lines;

extending each line in the set of lines a predetermined distance to generate an extended set of lines;

determining locations of all intersection points of the extended set of lines; and

determining a PCD centerline of the given PCD based on the determined locations of the intersection points.

2. The method of claim 1 , wherein the step of determining the PCD centerline comprises determine the PCD centerline using a least-squares fit of the locations of the intersection points.

3. The method of claim 1 , further comprising:

determining a center position of the given PCD by calculating an average of the locations of the intersection points.

4. The method of claim 1 , further comprising:

repeating the obtaining, determining, generating, extending, determining, and determining steps of claim 1 for each PCD in the plurality of PCDs.

5. An apparatus for determining, for a fourth-generation computed tomography (CT) scanner that includes a third-generation X-ray source and detector system and a plurality fixed, sparse photon-counting detectors (PCDs), a position of each PCD of the plurality of PCDs, the apparatus comprising:

a processing circuit configured to

obtain, for a given PCD of the plurality of PCDs, sinogram data from a reference scan of a plurality of line attenuators arranged at fixed, known positions within the CT scanner;

determine, by analyzing the sinogram data, a set of view angles of the X-ray source for which the sinogram data exhibits a decrease in count value, indicating a shadow cast by one of the line attenuators;

generate, for each view angle in the set of view angles, a line connecting a position of the X-ray source at the view angle, and a position of a line attenuator, of the plurality of line attenuators, that is closest to the position of the X-ray source at the view angle, to generate a set of lines;

extend each line in the set of lines a predetermined distance to generate an extended set of lines;

determine locations of all intersection points of the extended set of lines; and

determine a PCD centerline of the given PCD based on the determined locations of the intersection points.

6. A method for determining, for a fourth-generation computed tomography (CT) scanner that includes a third-generation X-ray source and detector system and a plurality fixed, sparse photon-counting detectors (PCDs), a position of each PCD of the plurality of PCDs, the method comprising:

determining, for a given PCD of the plurality of PCDs, a set of view angles at which the PCD will cast a shadow on the third-generation detector;

determining, for each view angle in the determined set of view angles, by analyzing projection data obtained from a reference scan, a corresponding shadow location on the third-generation detector caused by the given PCD, to determine a set of shadow locations;

generating, for each view angle in the set of view angles, a line connecting a position of the X-ray source at the view angle, and a corresponding shadow location of the set of shadow locations, to generate a set of lines;

determining locations of all intersection points of the set of lines; and

determining a PCD centerline of the given PCD based on the determined locations of the intersection points.

7. The method of claim 6 , wherein the step of determining the PCD centerline comprises determine the PCD centerline using a least-squares fit of the locations of the intersection points.

8. The method of claim 6 , further comprising:

determining a center position of the given PCD by calculating an average of the locations of the intersection points.

9. The method of claim 6 , further comprising:

repeating the determining, determining, generating, determining, and determining steps of claim 6 for each PCD in the plurality of PCDs.

10. An apparatus for determining, for a fourth-generation computed tomography (CT) scanner that includes a third-generation X-ray source and detector system and a plurality fixed, sparse photon-counting detectors (PCDs), a position of each PCD of the plurality of PCDs, the apparatus comprising:

a processing circuit configured to

determine, for a given PCD of the plurality of PCDs, a set of view angles at which the PCD will cast a shadow on the third-generation detector;

determine, for each view angle in the determined set of view angles, by analyzing projection data obtained from a reference scan, a corresponding shadow location on the third-generation detector caused by the given PCD, to determine a set of shadow locations;

generate, for each view angle in the set of view angles, a line connecting a position of the X-ray source at the view angle, and a corresponding shadow location of the set of shadow locations, to generate a set of lines;

determine locations of all intersection points of the set of lines; and

determine a PCD centerline of the given PCD based on the determined locations of the intersection points.