Can gallium-68 compounds partly replace (18)F-FDG in PET molecular imaging?

The development of gallium-68 -1,4,7,10-tetraazacyclodecane-1,4,7,10-tetraacetic acid ((68)Ga-DOTA) compounds was made possible due to the chemistry of (68)Ga, which matches the pharmacokinetics of many peptides, specially the chelators DOTA and DOTAderivatives with the formation of stable (68)Ga (3+) complexes. The availability of this tracer from a germanium-68-gallium-68 generator with a relatively long half-life makes it attractive to use in busy nuclear medicine departments, particularly those with limited access to cyclotrons. The recent clinical experience with (68)Ga-peptides includes imaging neuroendocrine tumours particularly carcinoid, as well as neuroectodermal tumours such as phaeochromocytoma and paraganglioma. In vitro and animal testing are still progressing alongside clinical studies, with promising results in the use of (68)Ga-DOTA-rhenium-cyclized alpha-melanocyte stimulating hormone (MSH) and (68)Ga-DOTA-napamide (NAP) in melanoma, (68)Ga-DOTA-PEG(4)-BN(7-14) (PESIN) for the imaging of bombesin receptor- positive tumours and (68)Ga-ethylene dicysteine-metronidazole (EC-MN) for imaging tumour hypoxia. In addition to tumours, (68)Ga- DOTA peptide inhibitor of vascular peptide protein 1(VAP-P1) is being assessed for imaging inflammatory reaction. An additional value following a positive scan is the use of beta emitters labelled to the same peptides for radionuclide treatment. In conclusion, the recent introduction of (68)Ga-peptides, made available by a convenient (68)Ga/(68)Ge generator, could greatly contribute to the management of a wide range of clinical conditions including tumours and inflammation.