Molecular Sensing Using Hyperpolarized Xenon NMR Spectroscopy

Although proton-based magnetic resonance imaging (MRI) provides a powerful modality for clinical imaging with excellent spatial resolution, it is not well suited to imaging void spaces (i.e., the lungs), low-abundance molecular markers of disease, or environments where unique proton spin densities are low. To address this limitation, hyperpolarized (hp) xenon-based NMR spectroscopy and MRI have emerged as attractive alternatives. Early studies probed xenon adsorbed to surfaces, which required hyperpolarization for sensitivity. The first biological application, pulmonary void-space imaging, came in 1994 by Albert et al., who used xenon to image a mouse lung. Subsequently, there have been many examples of xenonbased imaging of the lung, brain, and other tissues in both mice and humans. Although these examples established the clinical relevance of xenon, there were still challenges associated with delivering xenon to specific locations of interest; a prerequisite for targeted molecular imaging applications. Herein, we discuss the advantages of employing xenon for molecular imaging by first describing its unique physical properties and then describing a general strategy for use in detecting specific targets of interest. 2 Physical Properties of Xenon