Medical Applications of Hyperpolarized and Inert Gases in MR Imaging and NMR Spectroscopy

Abstract

MRI is a potentially ideal imaging modality for non-invasive, non-ionizing, and longitudinal assessment of disease. One notable disadvantage of MRI is its low sensitivity compared to other imaging modalities, and this drawback can be rectified with hyperpolarized (HP) agents that have been developed over the past 20 years. HP agents have the potential to vastly improve MRI sensitivity for the diagnosis and management of various diseases. The polarization of NMR-sensitive nuclei other than 1H (e.g. 3He, 129Xe) can be enhanced by a factor of up to 100 000 times above thermal equilibrium levels, thus enabling direct detection of the HP agent at low concentration and with no background signal. In this chapter, a number of HP media applications in MR imaging is discussed, including HP 3He and 129Xe lung imaging, HP 129Xe brain imaging, and HP 129Xe biosensors. Inert fluorinated gas MRI, which is a new lung imaging technique that does not require hyperpolarization, is also briefly discussed. These techniques will likely be important future directions for the HP gas lung imaging community.