What is angiography?
Angiography is a diagnostic test that produces an X-ray movie of the blood vessels and the blood flowing through them. Angiography of the head ( cerebral angiography) is used to diagnose stroke by revealing abnormalities such as narrowing or blockage of the brain's blood vessels or bleeding in the brain. Angiography of the neck (carotid angiography) looks at the two large carotid arteries—one on each side of the neck—that supply blood to the brain. Narrowing in the carotid arteries reduces blood flow, and fatty deposits on the artery walls can break off, causing a stroke.
The location of the carotid artery on one side of the neck (NINDS)
To perform the test, a long, thin tube called a catheter is inserted into an artery in your groin or arm and guided to the area to be studied. The catheter is used to inject a dye into the blood vessels of your head and neck, and the dye is filmed by an X-ray camera, producing an angiogram—an X-ray movie of your vessels as the blood moves through them.
Angiogram image of a narrowed carotid artery (A) and the same artery after it was opened with a stent (B)