Monitoring of the tumor oxygen status by EPR oxygen imaging. A, B, T2-weighted anatomy of C3H mice bearing SCCVII tumors, and tumor pO2 and EPR tracer level maps in the tumor scanned every 15 min after intravenous administration of SQAP (A) or saline (B). C, D, Plots of median pO2 value (mmHg) and tracer level as image intensity (arbitrary units; a.u.) after the SQAP (C) or saline (D) injection. E–H, T2-weighted anatomy and EPRI pO2 maps of SCCVII/C3H and A549/nude mice before (0 min) and 30 min after SQAP injection. I, Changes in median pO2 value (ΔpO2 mmHg) 30 min after injection.