CD47 and neoplasm: To confirm that the observed tumor enhancement on ferumoxytol-enhanced MR images was due to ferumoxytol nanoparticle compartmentalization in TAM, we injected osteosarcoma-bearing mice with fluorescein isothiocyanate (FITC)-tagged ferumoxytol and obtained fluorescence microscopy images after CD47 mAb or sham treatment: FITC-conjugated ferumoxytol was found in F4/80+ TAMs of all tumors and the corresponding intensity of FITC-ferumoxytol per tumor and per macrophage was significantly higher in CD47 mAb-treated tumors compared to sham-treated controls (p = 0.002, Fig. 6a, b).