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 (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 (3) He, are sensitive to pulmonary ischemia in rats, confirming the findings in studies performed in large animal models of pulmonary ischemia.

Using hyperpolarized 3He MRI to evaluate treatment efficacy in cystic fibrosis patients.

PURPOSE: To use hyperpolarized (HP) (3)He MR imaging to assess functional lung ventilation in subjects with cystic fibrosis (CF) before and after treatment. MATERIALS AND METHODS: We performed HP (3)He static ventilation MRI scans on three subjects, using a Philips 3.0 Tesla (T) Achieva MRI scanner, before and after 11 days of in-patient treatment with combined intravenous and inhaled therapies for pulmonary exacerbations of CF. We also collected spirometry data. We quantified pulmonary ventilation volume measured with HP (3)He MRI using an advanced semi-automated analysis technique. RESULTS: Following 11 days of treatment with intravenous antibiotics, hypertonic saline, and rhDNase, HP (3)He MR images in one subject displayed a 25% increase in total ventilation volume. Total ventilation volume in the other two subjects slightly decreased. All three subjects showed increases in FEV(1) and FVC following treatment. CONCLUSION: In all subjects, the HP (3)He MR images provided detailed information on precisely where in the lungs gas was reaching. These data provide additional support for the conclusion that HP noble gas MRI can be a powerful tool for evaluating lung ventilation in patients with cystic fibrosis, but also raise important questions about the correlation between spirometry and HP gas MRI measurements.