Geometry calibration algorithm for large flat module detector CT scanner

An apparatus for geometric calibration of a CT scanner having at least one row of detector cells, the apparatus comprising:

• a geometric description establishing device configured to establish a complete geometric description of the CT scanner, the complete geometric description comprising at least one unknown geometric parameter;
• a forward projection function establishing device configured to establish a description of a forward projection function using the complete geometric description;
• an actual projection coordinate acquiring device configured to acquire actual projection coordinates of a calibration phantom placed in a scanning field of view (SFOV) on a current row of detector cells and corresponding to a plurality of angles, wherein the current row of detector cells has a structure of n×q×r, where n denotes the number of modules, q denotes the number of packs in each module, and r denotes the number of detector cells in each pack and the at least one unknown geometric parameter comprises sizes of (n−1) air gaps between adjacent modules, and an ISO channel offset;
• a calculated projection coordinate acquiring device configured to acquire calculated projection coordinates of the calibration phantom on the current row of detector cells and corresponding to the plurality of angles using the description of the forward projection function;
• and
• a calibrated value acquiring device configured for acquire a calibrated value for the at least one unknown geometric parameter by evaluating the at least one unknown geometric parameter based on the acquired actual projection coordinates and calculated projection coordinates via a nonlinear least square fitting algorithm.

A CT scan system, comprising:

• an apparatus for geometric calibration of a CT scanner having at least one row of detector cells
• the apparatus comprising:
• a geometric description establishing device configured to establish a complete geometric description of the CT scanner, the complete geometric description comprising at least one unknown geometric parameter;
• a forward projection function establishing device configured to establish a description of a forward projection function using the complete geometric description;
• an actual projection coordinate acquiring device configured to acquire actual projection coordinates of a calibration phantom placed in a scanning field of view (SFOV) on a current row of detector cells and corresponding to a plurality of angles, wherein the current row of detector cells has a structure of n×q×r, where n denotes the number of modules, q denotes the number of packs in each module, and r denotes the number of detector cells in each pack and the at least one unknown geometric parameter comprises sizes of (n−1) air gaps between adjacent modules, and an ISO channel offset;
• a calculated projection coordinate acquiring device configured to acquire calculated projection coordinates of the calibration phantom on the current row of detector cells and corresponding to the plurality of angles using the description of the forward projection function;
• and
• a calibrated value acquiring device configured for acquire a calibrated value for the at least one unknown geometric parameter by evaluating the at least one unknown geometric parameter based on the acquired actual projection coordinates and calculated projection coordinates via a nonlinear least square fitting algorithm.