Fludeoxyglucose (18F) (INN), or fludeoxyglucose F 18 (USAN and USP), also commonly called fluorodeoxyglucose and abbreviated FDG, 18F-FDG or FDG, is a radiopharmaceutical used in the medical imaging modality positron emission tomography (PET). Chemically, it is 2-deoxy-2-(18F)fluoro-D-glucose, a glucose analog, with the positron-emitting radioactive isotope fluorine-18 substituted for the normal hydroxyl group at the 2' position in the glucose molecule.