Fluorine-18
 Decay over 24 hours | |
| General | |
|---|---|
| Symbol | 18F |
| Names | fluorine-18, 18F, F-18, Fluorine-18 |
| Protons (Z) | 9 |
| Neutrons (N) | 9 |
| Nuclide data | |
| Natural abundance | Radioisotope |
| Half-life (t1/2) | 109.771(20) min |
| Isotope mass | 18.0009380(6) Da |
| Spin | 1+ |
| Excess energy | 873.431 keV |
| Binding energy | 137369.199 keV |
| Decay products | 18O |
| Decay modes | |
| Decay mode | Decay energy (MeV) |
| Positron emission (97%) | 0.6335 |
| Electron capture (3%) | 1.6555 |
| Isotopes of fluorine Complete table of nuclides | |
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.
Synthesis
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.
Chemistry
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.
Applications
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.
References
- ^ 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.
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