Multimodality functional imaging of spontaneous canine tumors using 64Cu-ATSM and 18FDG PET/CT and dynamic contrast enhanced perfusion CT

To compare the distribution and uptake of the hypoxia tracer (64)Cu-diacetyl-bis(N(4)-methylthiosemicarbazone) ((64)Cu-ATSM) PET/CT, FDG PET/CT and dynamic contrast enhanced perfusion CT (DCE-pCT) in spontaneous canine tumors. In addition (64)Cu-ATSM distribution over time was evaluated. Nine spontaneous cancer-bearing dogs were prospectively enrolled.

FDG (1h pi.) and (64)Cu-ATSM (3 and 24h pi.) PET/CT were performed over three consecutive days. DCE-pCT was performed on day 2. Tumor uptake of FDG and (64)Cu-ATSM was assessed semi-quantitatively and the distribution of FDG, (64)Cu-ATSM and CT perfusion parameters correlated. (64)Cu-ATSM distribution on scans performed 24h apart displayed moderate to strong correlation; however, temporal changes were observed.

The spatial distribution pattern of (64)Cu-ATSM between scans was moderately to strongly positively correlated to FDG, whereas the correlation of CT perfusion parameters to FDG and to (64)Cu-ATSM yielded more varying results. (64)Cu-ATSM uptake was positively correlated to FDG. (64)Cu-ATSM was found to be relatively stable between PET scans performed at different time points, important temporal changes were however observed in hypo-perfused regions.

These findings potentially indicate that prolonged uptake periods for (64)Cu-ATSM imaging may be needed. Although a moderate to strong correlation between (64)Cu-ATSM and FDG PET/CT is observed, the two tracers provide different biological information with an overlapping spatial distribution.