To measure the geometry parameters from a sparse projection data set of a stack of beads. In cone-beam tomography, the projections are distorted by the perspective the divergent beam is producing. This means that geometry is essential to the successful reconstruction of tomography. The center of rotation and the pixel size (this is only needed to scale the attenuation coefficients) which is the only information required for parallel beam reconstruction. For cone-beam reconstruction, you further need to know the distances from the source to the sample (object), the distance from the source to the detector (SDD). These parameters define the magnification of the configuration and would in principle be sufficient for the reconstruction. The beam usually doesn’t hit the detector perpendicularly, therefore we also need to know the position of the piercing point on the detector px and py.

1. COR - Center of Rotation
2. CTilt - Tilt of the Rotation Axis
3. SOD - Source Object Distance
4. SDD - Source Detector Distance
5. PP - Piercing Point