Intra-tumoral distribution of 64Cu-ATSM: a comparison study with FDG

64Cu-labeled diacetyl-bis(N4-methylthiosemicarbazone) (64Cu-ATSM) is a promising agent for internal radiation therapy and imaging of hypoxic tissues. In the present study, the intra-tumoral distribution of 64Cu-ATSM was investigated by comparing it to that of [18F]FDG and histological findings. VX2 tumors were implanted into Japanese white rabbits subcutaneously. 64Cu-ATSM and [18F]FDG were co-injected intravenously and the tumor was dissected and cut into 1 mm thick slices 1 h after the injection. The uptake of 64Cu-ATSM and [18F]FDG was measured using a dual-tracer autoradiographic technique. Histological cell biology was estimated from the optical microscopy of tumor sections. The major accumulation of 64Cu-ATSM was observed around the outer rim of the tumor masses which consisted mainly of active cells and expected to be hypoxic. [18F]FDG was distributed more widely with highest levels in the inner regions where pre-necrotic cells were mainly observed. 64Cu-ATSM appears to be useful for the detection of hypoxic but active tumor cell regions in vivo