A method is presented which allows for the accurate extraction of regional functional metrics in rodent lungs using hyperpolarized gas. The technique is based on the combination of measured T1 decay, an independent measure of specific ventilation and mass balance considerations to extract the regional oxygen levels and uptake. In phantom and animal experiments, it is demonstrated that the redistribution of gas during the measurement is a significant confounding factor, and this effect is addressed analytically. The resulting parameterization of gas flow increases the accuracy of oxygen-sensitive MRI, and may also be used independently to assess air trapping and airway constriction. Limitations of the technique with respect to spatial resolution and robustness are also discussed. Copyright © 2011 John Wiley & Sons, Ltd.