This is an x-ray study of the body in which radiographic images of cross-sections of the body is obtained. CT scan of the brain may reveal tumor, infarction, hydrocephalus, cortical atrophy, cerebral aneurysm, hematoma, A-V malformation. Study of the chest may reveal tumor, lymph nodes, cysts, abscess, effusion, and aortic aneurysm. Study of the abdomen may reveal tumor, hematoma, cysts. In some studies the image can be improved by contrast dye. The major complication is allergy to the dye in some patients.