In the last post Working with KCT CBCT 1 we converted DICOM data to the DEN format and explained how volumes are encoded. Today we create a CT trajectory setup and encode it in the format that can be recognized in KCT. Finally, we use KCT to reproject the volume from the last post using this trajectory.

Theoretical scanning trajectory

Let's reproject the volume we have using theoretical C-Arm FDCT trajectory. Let's say that our device rotates along the axis parallel to the z axis. By angle $\omega$ we denote polar angle between normal to detector that is pointing towards the source and x axis. Let's fix source to isocenter and source to detector lengths and create a setup in which patient is irradiated from 360 different angles corresponding to integer $\omega$ values. Let's create (camera matrices)[https://en.wikipedia.org/wiki/Camera_matrix], which encode this setup. We create them as float64 DEN files, where z dimension will represent number of angles. So that we produce file of dimensions (dimx, dimy, dimz)=(3,4,360).

Volume reprojection

Use the following command

cllin-projector --cvp --voxel-sizex 0.64453125 --voxel-sizey 0.64453125 --voxel-sizez 1.5 --projection-sizex 616 --projection-sizey 480 DEN_RAW/Series_00.den CM.den Series_00.proj