[18F]Fluoride : molar activity and utility in radiosynthesis and in biological applications

Abstract

A radiopharmaceutical is a radioactive isotope combined with a biologically interesting molecule that targets specific tissues, organs, or cells in the living body. This special class of medicinal product has applications in both diagnostics and therapy. Positron emission tomography (PET) is a powerful non-invasive imaging technique that utilises gamma rays generated by short-lived positron emitting radioisotopes to form an image of the distribution of radioactivity in the subject. [18F]Fluorine is one of the most widely used PET radionuclides.

Molar activity (Am) is an important parameter that needs to be evaluated when producing PET radiopharmaceuticals. The amount of stable nuclide must be minimized in order to obtain a high Am, which is an especially desirable property when imaging receptors. This study showed that the tubing used to transport the starting material, [18F]fluoride, from the production chamber to the radiosynthesis device can be a source of stable fluorine; thus, fluorinated tubing material should be avoided.

The development of a new synthesis method, such as [18F]FTHA, is strictly regulated by good manufacturing practices (GMP) guidelines, including validation of the synthesis and analytical methods.

The radioactive label (i.e., [18F]fluoride) becomes detached from the molecule during its metabolism and will accumulate in bone and soft tissues. Studies conducted with healthy rats have demonstrated that this uptake is highly variable in various bone types and soft tissues in rats.

In conclusion, the production and use of PET radiopharmaceuticals involve a multistage process, and the studies presented here reflect the different aspects of this process.