"Radiography" is a general term; "CT scan" is more specific. In current usage, "CT scan" is a scanning x-ray--a particular type of radiography. However, "radiography" includes x-ray techniques other...
They are the same thing. CAT stands for Computerized Axial Tomography which was later changer to just CT or rather Computerized Tomography. The scanners originaly only did axial images (referring to...