Mice imaged with optical and PET modalities. Nude mice bearing A431 human tumor xenografts at the hind legs were imaged 24 h post-injection of the imaging probe, i.e., 89Zr-cetuximab + cetuximab-IR. (a) Optical images taken with IVIS Lumina at 1-s exposure time and ICG filter sets. (b) PET images representative of the entire scan (1 h), coronal view. Tumors are indicated with arrows. Individual tumor weights determined at the end of the experiment, from left (L) to right (R), are as follows: mouse 1: L 0.2544 g, R 0.4353 g; mouse 2: L 0.4176 g, R 0.243 g; mouse 3: L 0.529 g, R 0.2163 g; mouse 4: L 0.5474 g, R 0.2972 g.