Ultrafast MR-imaging of lung ventilation using hyperpolarized helium-3.

Assessment of the temporal: and spatial dynamics of hyperpolarized Helium-3 (3He) distribution in the lung with ultrafast gradient-echo magnetic-reson ance imaging, Material and Methods: Coronal images of the lung were,acquire d using ultrafast gradient-echo pulse sequences with TR/TE = 3.3 ms/1.3 ms (slice thickenss, 40 mm) and TR/TE = 2.0 ms/0.7 ms (without slice selection ). A series of 80 or 160 projection images was obtained with 210 ms or 130 ms temporal resolution, respectively. Imaging was performed during several respiratory cycles after application of a single bolus of 300 mL hyperpolar ized 3He. Measurements were performed in six healthy volunteers (spontaneou s breathing). Results: Different phases of in- and expiration could be visu alized.; During the course of consecutive respiratory cycles the 3He signal decreased due to dilution of 3He in residual alveolar gas and by inspired air, relaxation due to oxygen and the RF pulses; and due to Helium-3 washou t. The signal of a single bolus of 3He was detected in the lung for up to f our respiratory cycles. Anatomical structures were better visualized on sli ce selective images than on images without slice selection. Conclusion: Dis tribution of inspired 3He within the tracheobronchial tree and alveolar spa ce and its washout can be visualized by ultrafast imaging of a single bolus of hyperpolarized 3He gas. This method may allow for regional analysis of lung function with temporal and spatial resolution superior to conventional methods.