NCIt definition : An amino acid analog radiolabeled with fluorine F 18, a positron emitting isotope,
used as a tracer in positron emission tomography (PET). Reflecting the increased amino
acid transport capacity of tumor cells, F-18 fluroethyltyrosine (F-18 FET) is actively
taken up in tumor cells via the amino acid transport system, but is neither incorporated
into proteins nor readily degraded, resulting in high intracellular concentrations
of this imaging agent. Radiolabeled amino acid-based agents are useful in PET brain
tumor imaging because F-18 fluoro-deoxyglucose (F-18 FDG), commonly used in PET tumor
imaging, is relatively insensitive for detecting tumors in the brain due to high levels
of glycolytic metabolism in the normal cortex and to a lesser extent in white matter.;