Dynamic functional lung MRI using hyperpolarized gases

Magnetic resonance imaging using signal from hyperpolarized noble gases, is proving to be an important technique for imaging airway disease. Pulmonary disease results in considerable morbidity and mortality, and techniques that yield high contrast images of the lungs are crucial to its diagnosis and staging. Many of the available imaging modalities, however, lack sensitivity and disease specificity. MRI is noninvasive, and can produce slice selective and 3-D images, but imaging of the lung presents obstacles for conventional proton MRI both because the gas space is water-free, and because protons have an inconveniently short T2* in lung tissue due to the magnetically inhomogeneous environment. After inhalation of a hyperpolarized noble gas, however, the airways and alveolar gas spaces can be imaged with high SNR by MRI. Imaging lung perfusion and lung parenchyma should also be possible. This talk focuses on the development and clinical applications of hyperpolarized gas MRI, reviews the results to date, and discusses future directions of this technique. The first clinical studies indicate that hyperpolarized gas MRI is effective for diagnosis of pulmonary disease. Continued technical improvements, e.g., the production of larger volumes of gas at higher polarization, optimized pulse sequences, and specialized RF coils, should enable ¹²⁹Xe imaging of lung perfusion and lung parenchyma and provide improved detection of pulmonary disease