68Ga-PET: a powerful generator-based alternative to cyclotron-based PET radiopharmaceuticals

Abstract

PET (positron emission tomography) is a powerful diagnostic and imaging technique which requires short-lived positron emitting isotopes. The most commonly used are accelerator-produced 11C and 18F. An alternative is the use of metallic positron emitters. Among them 68Ga deserves special attention because of its availability from long-lived 68Ge/68Ga generator systems which render 68Ga radiopharmacy independent of an onsite cyclotron. The coordination chemistry of Ga3+ is dominated by its hard acid character. A variety of mono- and bifunctional chelators have been developed which allow the formation of stable 68 Ga3+ complexes and convenient coupling to biomolecules. 68Ga coupling to small biomolecules is potentially an alternative to 18F- and 11C-based radiopharmacy. In particular, peptides targeting G-protein coupled receptors overexpressed on human tumour cells have shown preclinically and clinically high and specific tumour uptake. Kit-formulated precursors along with the generator may be provided, similar to the 99Mo/99mTc-based radiopharmacy, still the mainstay of nuclear medicine.