Hyperpolarized-gas MRI using 3He or 129Xe is an evolving technology for providing images of the lung with high spatial and temporal resolution. It's non-invasive and free of ionizing radiation, so particularly suited for evaluating lung disease progression and treatment efficacy. This book presents a novel lung imaging technique, which for the first time permits quantitative regional assessment of both gas delivery to the alveolar airspaces (ventilation) and gas uptake into lung parenchyma and blood (gas exchange) for human, using hyperpolarized 129Xe MRI. Also two techniques that can potentially improve the imaging speed of hyperpolarized gas study are demonstrated.