Some disease processes affect the blood vessels of the brain. These diseases include: Aneurysms ' a weakness in the wall of an artery that can then rupture and bleed, Arteriovenous malformations (AVM's) ' an abnormal tangle of blood vessels, and vasculitis ' an abnormal inflammation of the brain blood vessels. The gold standard for assessing these diseases is a 'cerebral angiogram'. This test involves injecting dye into the blood vessels of the brain and then taking many X-rays of these vessels. The patient lies flat on a table and a catheter is inserted into an artery in the groin. The catheter is then passed through the arterial system to the head where the dye can be injected. This is a usually a painless procedure.