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

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 C-11 and F-18. An alternative is the use of metallic positron emitters. Among them Ga-68 deserves special attention because of its availability from long-lived Ge-68/Ga-68 generator systems which render Ga-68 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 Ga-68(3+) complexes and convenient coupling to biomolecules. Ga-68 coupling to small biomolecules is potentially an alternative to F-18- and C-11-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 Mo-99/Tc-99m-based radiopharmacy, still the mainstay of nuclear medicine. Copyright (c) 2008 John Wiley & Sons, Ltd.