Compounds containing fluorine-18, a radioactive isotope that emits positrons, are often used in positron emission tomography (PET) scanning, because the isotopes half-life of about 110 minutes is usefully long by positron-emitter standards. One such radiopharmaceutical is 2-deoxy-2-(F)fluoro-D-glucose (generically referred to as fludeoxyglucose), commonly abbreviated as F-FDG, or simply FDG. In PET imaging, FDG can be used for assessing glucose metabolism in the brain and for imaging cancer tumors. After injection into the blood, FDG is taken up by "FDG-avid" tissues with a high need for glucose, such as the brain and most types of malignant tumors. Tomography, often assisted by a computer to form a PET/CT (CT stands for "computer tomography") machine, can then be used to diagnose or monitor treatment of cancers, especially Hodgkins lymphoma, lung cancer, and breast cancer.
Natural fluorine is monoisotopic, consisting solely of fluorine-19. Fluorine compounds are highly amenable to nuclear magnetic resonance (NMR), because fluorine-19 has a nuclear spin of , a high nuclear magnetic moment, and a high magnetogyric ratio. Fluorine compounds typically have a fast NMR relaxation, which enables the use of fast averaging to obtain a signal-to-noise ratio similar to hydrogen-1 NMR spectra. Fluorine-19 is commonly used in NMR study of metabolism, protein structures and conformational changes. In addition, inert fluorinated gases have the potential to be a cheap and efficient tool for imaging lung ventilation.