Fluorine-18 (18F) is a fluorine radioisotope which is an important source of positrons. It has a mass of 18.0009380(6) u and its half-life is 109.771(20) minutes. It decays by positron emission 97% of the time and electron capture 3% of the time. Both modes of decay yield stable oxygen-18.
Decay over 24 hours
|Isotope mass||18.0009380(6) u|
|Excess energy||873.431± 0.593 keV|
|Binding energy||137369.199± 0.593 keV|
|Decay mode||Decay energy|
|Positron emission (97%)||0.6335 MeV|
|Electron capture (3%)||1.6555 MeV|
In the radiopharmaceutical industry, F-18 is made using either a cyclotron or linear particle accelerator to bombard a target, usually of pure or enriched oxygen-18-water  with high energy protons (typically ~18 MeV protons). The fluorine produced is in the form of a water solution of F-18 fluoride, which is then used in a rapid chemical synthesis of the radiopharmaceutical. The organic O-18 pharmaceutical molecule is not made before the production of the radiopharmaceutical, as high energy protons destroy such molecules. Radiopharmaceuticals using fluorine must therefore be synthesized after the F-18 has been produced.
Fluorine-18 is often substituted for a hydroxyl group in a radiotracer parent molecule, due to similar steric and electrostatic properties. This may however be problematic in certain applications due to possible changes in the molecule polarity.
Fluorine-18 is an important isotope in the radiopharmaceutical industry, and is primarily synthesized into fluorodeoxyglucose (FDG) for use in positron emission tomography (PET scans). It is substituted for hydroxyl and used as a tracer in the scan. Its significance is due to both its short half-life and the emission of positrons when decaying.
|Fluorine-18 is an
isotope of fluorine
|Decay product of: