Coronal slice microPET/CT images. Images of athymic mice with s.c. human tumor xenografts (arrows) with increasing HER2 expression at 24 h p.i. of 22 MBq (10 μg) 64Cu-DOTA-trastuzumab [panels (a), (b), (c)] or 64Cu-DOTA-rituximab Fab [panel (d)]. (a) Mouse with MDA-MB-231 and BT-20 xenografts implanted on the left and right flanks, respectively with low HER2 density (5.4 × 104 and 1.6 × 105 receptors/cell, respectively). (b) Mouse with MDA-MB-361 xenograft with intermediate HER2 density (5.1 × 105 receptors/cell). (c) Mouse with 15 to 18 mm diameter (left) and 5 to 10 mm diameter (right) SK-OV-3 xenografts with high HER2 density (1.2 × 106 receptors/cell). (d) Mouse with MDA-MB-361 xenograft with intermediate HER2 density (5.1 × 105 receptors/cell). Bladder radioactivity seen in one mouse is indicated by a broken arrow. Image acquisition time was 20 min and anaesthesia was induced and maintained by inhalation of 2% isoflurane in oxygen. Images were adjusted to approximately equal intensity.