RTN4R and neoplasm: While in the case of the A549 tumour-bearing mice, the hepatic [68Ga]Ga-DOTA-NGR concentration was only 0.2% ID/g at the early time points, the respective liver uptake values for [64Cu]Cu-DOTA-NGR1 and [64Cu]Cu-DOTA-NGR2 in receptor positive HT1080 tumour xenografts were 6.39 ± 0.41% ID/g and 6.49 ± 0.39% ID/g [41,55].