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

Abstract

Purpose In this study, a new model of pulmonary embolism in rats was developed and tested, to examine if hyperpolarized (HP) 3He MR images can measure impairment of the exchange of oxygen from the airspaces to the blood during pulmonary embolism. Methods HP 3He 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 3He MR images were used to calculate the initial partial pressure of oxygen (pO) and the rate of oxygen depletion (R) in rat lungs. Results The pO was significantly higher in the ischemic lung than in the contralateral normal side, and pO 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 pO and R, as measured by the T1 decay of HP 3He, are sensitive to pulmonary ischemia in rats, confirming the findings in studies performed in large animal models of pulmonary ischemia.