# Create a simulated geometry rtksimulatedgeometry -n 180 -o geometry.xml # Forward project rtkforwardprojections -g geometry.xml -o projections.mha -i 00.mhd --spacing 2 --dimension 512 # Reconstruct in the same resolution as the original rtkfdk -p . -r projections.mha -o fdk.mha -g geometry.xml --spacing=0.976562,0.976562,2 --origin=-250,-250,-164.5 --dimension=512,512,141
Note that the original file is in Hounsfield units which explains the negative values in the projection images since, e.g., the attenuation of air is -1000 HU.
It is also worth of note that the file is oriented in the DICOM coordinate system although RTK uses the IEC 61217 which results in a rotation around the antero-posterior axis of the patient. This can be easily changed by modifying the TransformMatrix in the 00.mhd file.