I have had a ct scan angiogram and cath. My ct scan was more inclusive as it took images of the lungs, heart and thorax. It showed the complete anatomy of the heart vessels that included any soft plaque within the lining of the vessel. The ct software scored the soft plaque and evaluated the risk of a rupture. It also discloses any hard plaque within the lumen (vessel channel).
The cath views the lumen for plaque, and has the ability to determine gradient pressures of chambers and vessels...The cath can also be equiped with ultra sound to view the anatomy of the vessel.