Chemistry of β +-Emitting Compounds Based on Fluorine-18

Abstract

Positron emission tomography (PET) is a non-invasive imaging technology which provides a unique window on the physiology and function of living organisms. It uses short-lived positron emitting isotopes to trace labelled compounds in vivo. Among those radioisotopes, fluorine-18 is a nuclide of choice: it has a longer half-life (110 min) and a positron energy (0.635 MeV) lower than the other commonly used positron emitter, carbone-11 (t1/2: 20 min, 0.96 MeV). This makes fluorine-18 very attractive in terms of synthesis time, biological studies and resolutions of PET scans. Fluorine-18 is generally produced in a cyclotron via the 20Ne(d, α)18F or 18O(p,n)18F nuclear reactions. The availability of either labelled molecular fluorine [18F]F2 or labelled fluoride [18F]F- allows flexibility in the development of synthetic routes to organic compounds. However, [18F]fluoride which is available in high specific activity is preferred for most tracer applications. The aim of this review is to emphasise the scopes and limitations of the chemistry with fluorine-18. The synthetic methodology of the different 18F-labelled precursors, their uses in rapid reactions and the potential applications of the new 18F-radiopharmaceuticals are reviewed. Apart from basic publications, most references cited have been published in the past 10 years.