=====Fluorine=====
Fluorine is a chemical element with symbol [[F]] and atomic number 9. It is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. As the most electronegative element, it is extremely reactive: almost all other elements, including some noble gases, form compounds with fluorine.

see [[Fluorine 18]].
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Fluorodeoxyglucose (18F) (INN), or [[fluorodeoxyglucose]] F 18 (USAN and USP), also commonly called [[fluorodeoxyglucose]] and abbreviated [18F][[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.