Basics and Clinical Application of the MR Assessment of Ventilation

There is a growing motivation for imaging regional lung ventilation. Global measures of lung function such as spirometry are not able to distinguish patterns of obstruction and regional reversibility in response to intervention. Advantages of MRI for lung imaging include use of nonionizing radiation and flexibility for acquiring dynamic, multidimensional signal changes in response to changes in lung function. For these reasons, MRI is particularly attractive for longitudinal studies of chronic lung disease, especially in pediatric populations. There are two broad classes of ventilation imaging methods using MRI, which have matured over the past decade: proton-based methods and direct imaging of exogenous gases using multinuclear MRI and spectroscopy. This chapter will provide a review of the theory and rationale of ventilation imaging with MRI, results of clinical research in ventilation MRI, and emerging methods of ventilation imaging. Proton MRI ventilation imaging techniques covered in this chapter include deformable image registration, Fourier decomposition, and oxygen-enhanced methods. This chapter also covers ventilation techniques utilizing MRI of visible gas nuclei, including hyperpolarized gas MRI and perfluorinated gas MRI.