These are two separate examinations with different objectives. CT angiogram is non-invasive and done in a CT scanner. Whereas a catheter angiogram is an invasive procedure. CT angiogram depicts coronary vessels nicely with visualization of calcified/non-calcified plaques and has a very high negative predictive value (95-100 %). Hence this examination is more suitable to rule out coronary artery disease non-invasively. Get the finest treatment at the top radiology hospital in Delhi.