A brain scan is a method of imaging that us used to detect brain metastases (i.e., cancer that has spread from another site, such as the breast, to the brain).
Brain scanning is performed in an outpatient setting. A small amount of a radioactive substance is injected into a vein. Images taken show whether the radioactivity collects in any areas of the brain. Accumulation of the radioactivity in part of the brain suggests the presence of an abnormality, such as a brain metastasis. Either a nuclear medicine physician (a doctor who specializes in the use of radioactive substances for diagnosis and treatment of disease) or a radiologist (a doctor who specializes in the use of radiation for diagnosis of disease) reads and interprets the brain scan.