The only different is the approach. Angiograms
have the catheter through
your artery, while the CT angio uses a canular in your arm
to inject dye. You will be alone in the room, and hear the operator through a loudspeaker in the scanner. They will ask you to hold your breath a few times, and keep still. They will also warn you to expect a burning sensation in your chest, or down one side of the body at times. So to pre-warn you of some things to expect during the procedure...