Angiography is an x-ray exam of the arteries used to diagnose blood vessel problems, such as blockages, narrowing, or bleeding. The catheter (tube) is inserted through a small nick in the skin, a contrast agent or x-ray dye is then injected to allow visibility of the blood vessels and arteries on the x-ray image. One of the more common uses of angiography is to determine whether a blockage or narrowing in the blood vessels is interfering with the normal flow of blood through the body. Often times, the interventional radiologist can also treat the blocked blood vessel with balloon angioplasty and thrombolysis (clot-dissolving) techniques. Other reasons for performing angiograms include aneurysms, cerebral vascular disease such as stroke or bleeding in the brain, or blood vessel malformations. Angiograms can also be used by surgeons to assist in planning an operation or choosing the appropriate surgical procedure.