an imaging method used to find anything that isn’t normal in the brain, including brain cancer and cancer that has spread to the brain from other places in the body. This scan can be done in an outpatient clinic. It is painless, except for the needle stick when a radioactive substance (radioisotope) is put into a vein. The radioactive substance can be seen in pictures as it collects in abnormal areas. See also outpatient, radioisotope.