Novel MRI applications of laser-polarized noble gases

Gas-phase nuclear magnetic resonance (NMR) has great potential as a probe for a variety of interesting physical and biomedical problems that are not amenable to study by water or similar liquid. However, NMR of gases was largely neglected due to the low signal obtained from the thermally polarized gases with very low sample density. The advent of optical pumping techniques for enhancing the polarization of the noble gases He-3 and Xe-129 has bought new life to this field, especially in medical imaging where He-3 lung inhalation imaging is approaching a clinical application. However, there are numerous applications in materials science that also benefit from the use of these gases. We review primarily nonmedical applications of laser-polarized noble gases for both NMR imaging and spectroscopy and highlight progress with examples from our laboratory including high-resolution imaging at millitesla applied field strength and velocity imaging of convective flow. Porous media microstucture has been probed with both thermal and laser-polarized xenon, as xenon is an ideal probe due to low surface interaction with the grains of the porous media.