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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.

Fluorine-18 decay.svg

Decay over 24 hours

Name, symbol Fluorine-18,18F
Neutrons 9
Protons 9
Nuclide data
Natural abundance Radioisotope
Half-life 109.771(20) min
Decay products 18O
Isotope mass 18.0009380(6) u
Spin 1+
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 [1] 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.

New dioxaborolane chemistry enables radioactive fluoride (18F) labeling of antibodies, which allows for positron emission tomography (PET) imaging of cancer.[2]


  1. ^ Fowler J. S. and Wolf A. P. (1982) The synthesis of carbon-11, fluorine-18 and nitrogen-13 labeled radiotracers for biomedical applications. Nucl. Sci. Ser. Natl Acad. Sci. Natl Res. Council Monogr. 1982.
  2. ^ Rodriguez, Erik A.; Wang, Ye; Crisp, Jessica L.; Vera, David R.; Tsien, Roger Y.; Ting, Richard (2016-04-27). "New Dioxaborolane Chemistry Enables [18F]-Positron-Emitting, Fluorescent [18F]-Multimodality Biomolecule Generation from the Solid Phase". Bioconjugate Chemistry. 27 (5): 1390–1399. doi:10.1021/acs.bioconjchem.6b00164. PMC 4916912Freely accessible. PMID 27064381.
Fluorine-18 is an
isotope of fluorine
Decay product of:
Decay chain
of fluorine-18
Decays to:

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