Science to practice: what does MR oxygenation imaging tell us about human breast cancer hypoxia?

The paradoxical relationship between blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging and breast cancer hypoxia challenges our current understanding of what we believe is happening to erythrocytes in tumors. The ability of air breathing R2* measurements to reflect tissue hypoxia appears to be tumor type-specific, which should prompt further exploration of this image contrast mechanism in both human and animal tumors.