Cerebral angiography is a procedure that uses a special dye (contrast material) and x-rays to see how blood flows through the brain. Doctors may order this test if symptoms or signs of vascular malformation (abnormal blood vessels), aneurysm (blood-filled dilation of a blood vessel), narrowing of the arteries in the brain, and vasculitis (inflammation of blood vessels) are present. Sometimes, it is also used to confirm a brain tumor, evaluate the arteries of the head and neck before surgery, and find a clot that may have caused a stroke.