For a CT with contrast, do not eat anything for 6 hours before the scan.
A CT angiography is a type of medical test that combines a CT scan with the injection of a special dye to produce pictures of blood vessels and tissues in a part of your body. The dye is injected through an intravenous (IV) line started in your arm or hand.
This helps in the diagnosis of the abnormalities of the aorta (largest blood vessel in the body & its branches).