Fig. 3.

Normalization bias effect. Since the integrated areas of absorptivity profiles of oxygenated and deoxygenated species are not equal, normalization introduces an unintended nonlinearity to recovered relative oxygenated and deoxygenated concentrations. Dotted lines represent true relative concentrations and by definition, true Mox is equal to “True Oxygenated”. True Mox decreases from left to right, as during ischemia. If the ratio of the integrated areas of oxygenated to deoxygenated absorptivity profiles were 4:1, the observed relative concentrations would be those shown by the solid lines. The observed Mox, equal to “Observed Oxygenated”, would be consistently overestimated.