Fluorodeoxyglucose

Glycolysis16 min (at 20%)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 radionuclide fluorine-18 substituted for the normal hydroxyl group at the C-2 position in the glucose molecule. 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 radionuclide fluorine-18 substituted for the normal hydroxyl group at the C-2 position in the glucose molecule. The uptake of 18F-FDG by tissues is a marker for the tissue uptake of glucose, which in turn is closely correlated with certain types of tissue metabolism. After 18F-FDG is injected into a patient, a PET scanner can form two-dimensional or three-dimensional images of the distribution of 18F-FDG within the body. Since its development in 1976, 18F-FDG had a profound influence on research in the neurosciences. The subsequent discovery in 1980 that 18F-FDG accumulates in tumors underpins the evolution of PET as a major clinical tool in cancer diagnosis. 18F-FDG is now the standard radiotracer used for PET neuroimaging and cancer patient management. The images can be assessed by a nuclear medicine physician or radiologist to provide diagnoses of various medical conditions. In 1968, Dr. Josef Pacak, Zdenek Tocik and Miloslav Cerny at the Department of Organic Chemistry, Charles University, Czechoslovakia were the first to describe the synthesis of FDG. Later, in the 1970s, Tatsuo Ido and Al Wolf at the Brookhaven National Laboratory were the first to describe the synthesis of FDG labeled with 18F. The compound was first administered to two normal human volunteers by Abass Alavi in August, 1976 at the University of Pennsylvania. Brain images obtained with an ordinary (non-PET) nuclear scanner demonstrated the concentration of 18F-FDG in that organ (see history reference below). Beginning in August 1990, and continuing throughout 1991, a shortage of oxygen-18, a raw material for FDG, made it necessary to ration isotope supplies. Israel's oxygen-18 facility had shut down due to the Gulf War, and the U.S. government had shut down its Isotopes of Carbon, Oxygen and Nitrogen facility at Los Alamos National Laboratory, leaving Isotec as the main supplier. FDG was first synthesized via electrophilic fluorination with F2. Subsequently, a 'nucleophilic synthesis' was devised with the same radioisotope. As with all radioactive 18F-labeled radioligands, the 18F must be made initially as the fluoride anion in a cyclotron. Synthesis of complete FDG radioactive tracer begins with synthesis of the unattached fluoride radiotracer, since cyclotron bombardment destroys organic molecules of the type usually used for ligands, and in particular, would destroy glucose. Cyclotron production of 18F may be accomplished by bombardment of neon-20 with deuterons, but usually is done by proton bombardment of 18O-enriched water, causing a (p,n) reaction (sometimes called a 'knockout reaction'—a common type of nuclear reaction with high probability where an incoming proton 'knocks out' a neutron) in the 18O. This produces 'carrier-free' dissolved fluoride (F−) ions in the water. The 109.8-minute half-life of 18F makes rapid and automated chemistry necessary after this point.