An x-ray or computer image (CT scan or MRI) of the blood vessels and blood flow in the body. A dye may be injected through a catheter (small tube) into an artery or vein to make the blood vessels easier to see. An angiogram may be used to check for an aneurysm (a bulge in a blood vessel wall), blockages in arteries, blood clots, or other problems, such as a tumor.