Evaluation of oxygen sensitivity of hyperpolarized helium imaging for the detection of pulmonary ischemia

Purpose In this study, a new model of pulmonary embolism in rats was developed and tested, to examine if hyperpolarized (HP) 3 He MR images can measure impairment of the exchange of oxygen from the airspaces to the blood during pulmonary embolism. Methods HP 3 He MRI was used to image six treatment‐group rats in which a branch of the pulmonary artery was embolized, and six control‐group rats. HP 3 He MR images were used to calculate the initial partial pressure of oxygen ( p O ) and the rate of oxygen depletion ( R ) in rat lungs. Results The p O was significantly higher in the ischemic lung than in the contralateral normal side, and p O was significantly higher in the ischemic lung than in both sides of the control lungs. Mean R in ischemic lungs was significantly lower than in the contralateral lungs, and mean R in ischemic lungs was also significantly lower than in both control lungs. Conclusion These results demonstrate that p O and R , as measured by the T 1 decay of HP 3 He, are sensitive to pulmonary ischemia in rats, confirming the findings in studies performed in large animal models of pulmonary ischemia. Magn Reson Med 75:2050–2054, 2016. © 2015 Wiley Periodicals, Inc.