fluoride18

Fluorine-18, commonly written as 18F, is a positron-emitting radionuclide of fluorine used predominantly in PET imaging. It decays to stable oxygen-18 by beta-plus emission, with a half-life of 109.8 minutes. The emitted positrons annihilate with electrons to produce two 511-keV gamma photons that are detected by PET scanners, enabling high-resolution images of metabolic and molecular processes.

18F is produced in cyclotrons by irradiating 18O-enriched water with protons through the 18O(p,n)18F reaction. The resulting [18F]fluoride is typically isolated in aqueous solution and incorporated into radiopharmaceuticals by nucleophilic substitution or other labeling strategies. The 110-minute half-life allows centralized production and distribution within a limited radius, though many centers prefer on-site or nearby cyclotrons.

The most widely used 18F-labeled radiopharmaceutical is [18F]fluorodeoxyglucose ([18F]FDG), a glucose analog that accumulates in tissues with increased glycolysis and is a standard tracer for cancer detection, staging, and monitoring. Other 18F tracers target different biological processes, including [18F]fluorodopa for dopaminergic function, [18F]FLT for cell proliferation, and [18F]FMISO for tumor hypoxia. In PET imaging, 18F tracers combine favorable imaging characteristics with established clinical workflows.

Safety and logistics: Like other radiopharmaceuticals, 18F-labeled tracers deliver small radiation doses and are administered under regulatory oversight with appropriate shielding and handling procedures. The relatively low positron energy and moderate half-life contribute to good image quality while enabling safer, more practical production and distribution compared with some other isotopes.