Fluorine-18

Fluorine-18, ¹⁸F
	Decay over 24 hours
General
Symbol	18F
Names	fluorine-18, F-18, Fluorine-18
Protons	9
Neutrons	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 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, fluorine-18 is made using either a cyclotron or linear particle accelerator to bombard a target, usually of pure or enriched [¹⁸O]water[1] with high energy protons (typically ~18 MeV protons). The fluorine produced is in the form of a water solution of [¹⁸F]fluoride, which is then used in a rapid chemical synthesis of the radiopharmaceutical. The organic oxygen-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 fluorine-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 one of the early tracers used in positron emission tomography (PET), having been in use since the 1960s.[2] Its significance is due to both its short half-life and the emission of positrons when decaying.

Tracers include sodium fluoride which can be useful for skeletal imaging as it displays high and rapid bone uptake accompanied by very rapid blood clearance, which results in a high bone-to-background ratio in a short time[3] and fluorodeoxyglucose (FDG), where the ¹⁸F substitutes a hydroxyl. New dioxaborolane chemistry enables radioactive fluoride (¹⁸F) labeling of antibodies, which allows for positron emission tomography (PET) imaging of cancer.[4] A Human-Derived, Genetic, Positron-emitting and Fluorescent (HD-GPF) reporter system uses a human protein, PSMA and non-immunogenic, and a small molecule that is positron-emitting (¹⁸F) and fluorescent for dual modality PET and fluorescence imaging of genome modified cells, e.g. cancer, CRISPR/Cas9, or CAR T-cells, in an entire mouse.[5]

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.
Blau, Monte; Ganatra, Ramanik; Bender, Merrill A. (January 1972). "18F-fluoride for bone imaging". Seminars in Nuclear Medicine. 2 (1): 31–37. doi:10.1016/S0001-2998(72)80005-9.
Ordonez, A. A.; DeMarco, V. P.; Klunk, M. H.; Pokkali, S.; Jain, S.K. (October 2015). "Imaging Chronic Tuberculous Lesions Using Sodium [18F]Fluoride Positron Emission Tomography in Mice". Molecular Imaging and Biology. 17 (5): 609–614. doi:10.1007/s11307-015-0836-6. PMC 4561601. PMID 25750032.
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 4916912. PMID 27064381.
Guo, Hua; Harikrishna, Kommidi; Vedvyas, Yogindra; McCloskey, Jaclyn E; Zhang, Weiqi; Chen, Nandi; Nurili, Fuad; Wu, Amy P; Sayman, Haluk B. (2019-05-23). "A fluorescent, [ 18 F]-positron-emitting agent for imaging PMSA allows genetic reporting in adoptively-transferred, genetically-modified cells". ACS Chemical Biology. 14: 1449–1459. doi:10.1021/acschembio.9b00160. ISSN 1554-8929. PMC 6775626. PMID 31120734.

Lighter: fluorine-17	Fluorine-18 is an isotope of fluorine	Heavier: fluorine-19
Decay product of: neon-18	Decay chain of fluorine-18	Decays to: oxygen-18

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[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] Blau, Monte; Ganatra, Ramanik; Bender, Merrill A. (January 1972). "18F-fluoride for bone imaging". Seminars in Nuclear Medicine. 2 (1): 31–37. doi:10.1016/S0001-2998(72)80005-9.

[3] Ordonez, A. A.; DeMarco, V. P.; Klunk, M. H.; Pokkali, S.; Jain, S.K. (October 2015). "Imaging Chronic Tuberculous Lesions Using Sodium [18F]Fluoride Positron Emission Tomography in Mice". Molecular Imaging and Biology. 17 (5): 609–614. doi:10.1007/s11307-015-0836-6. PMC 4561601. PMID 25750032.

[4] 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 4916912. PMID 27064381.

[5] Guo, Hua; Harikrishna, Kommidi; Vedvyas, Yogindra; McCloskey, Jaclyn E; Zhang, Weiqi; Chen, Nandi; Nurili, Fuad; Wu, Amy P; Sayman, Haluk B. (2019-05-23). "A fluorescent, [ 18 F]-positron-emitting agent for imaging PMSA allows genetic reporting in adoptively-transferred, genetically-modified cells". ACS Chemical Biology. 14: 1449–1459. doi:10.1021/acschembio.9b00160. ISSN 1554-8929. PMC 6775626. PMID 31120734.