⁶⁷Ga-9N₃uptake by xenografts of human melanotic melanoma in mice

Tumour uptake of the inert, neutral complex⁶⁷Ga-9N₃and the tumour:blood concentration ratio (l,4,7, triazacyclononane-l,4,7, triacetic acid) were measured in mice bearing xenografts of the human melanotic melanoma HX118. Between 1 and 4 h after the injection the tumour:blood ratio increased from 3.5 to 21 and the concentration of⁶⁷Ga-9N₃in the tumour decreased from 0.43 to 0.13% g^-1. During the first 24 h the concentration of⁶⁷Ga-9N₃in the tumour exceeded that in all other tissues except the liver and kidneys. The tumour:blood ratio and tissue distribution of⁶⁷Ga-9N₃at 4 h were compared with those of four other complexes. The results indicated that of the five complexes⁶⁷Ga-9N₃would be the most suitable for tumour imaging at early times after administration. Imaging would not be restricted to γ emitting⁶⁷Ga as there is also the possibility of using the 9N₃ligand to bind¹¹¹In for single photon emission computed tomography (SPECT),⁶⁸Ga for positron emission tomography (PET) or even stable Ga for direct in vivo nuclear magnetic resonance (NMR) detection.