CEACAM5 and neoplasm: In vivo, preferential localization of all [18F]AlF-radiofluorinated derivatives in CEA-expressing LS174T xenografts was observed, with a clearer visualization of CEA+ tumors with the Fab’ fragment and the dimeric fragment (tumor-to-blood ratio at 4 h p.i. = 5.87 ± 0.93 and 6.15 ± 1.58, respectively, vs 2.75 ± 0.18 for the diabody).