ERBB2 and neoplasm: In this study, we compared microSPECT/CT and microPET/CT for imaging s.c. human tumor xenografts expressing a wide range of HER2 density in athymic mice using trastuzumab Fab fragments modified with 1,4,7,10-tetraazacyclododecane N, N', N′′, N'′′-tetraacetic acid (DOTA) for complexing 111In or 64Cu.