positron emission tomography
[pahs-uh-trahn ee-mish-uhn tom-ahg-ruh-fee]
also called a PET scan. An imaging method that creates a picture of the body (or of biochemical events) after the injection of a very low dose of a radioactive substance that the body normally uses, such as a sugar. The scan then looks for areas of radiation in the body that might indicate tumors. (All cells use sugar, but high-grade tumors use more sugar than normal cells or low-grade tumors.) PET scans can help find tumors or see how well a known tumor is responding to treatment. The pictures are not very detailed, but they show the whole body at once. See also grade, imaging tests, nuclear medicine scan, radioisotope.