Hyperpolarized Magnetic Resonance Spectroscopy and Imaging

Abstract

Abstract The drive for increased sensitivity in magnetic resonance imaging (MRI) has lead to the development of a number of hyperpolarization techniques that are able to increase the polarization of spin systems far beyond their thermal value. This results in a transient enhancement of the magnetization to a highly nonequilibrium state, and thus an increase in MR detection sensitivity by many orders of magnitude. Hyperpolarized MRI offers a unique ability to image the spatial distribution of an injected substrate and to quantify its metabolic conversion in real-time in living cellular systems, perfused organs, or in vivo. In recent years there has been an explosion in the development of hyperpolarization techniques, brought about by improved understanding of the mechanisms involved in hyperpolarization and technological advances for hyperpolarization, as well as emerging biological and clinical applications. In particular, dissolution dynamic nuclear polarization (dDNP), parahydrogen induced polarization (PHIP), spin-exchange optical pumping (SEOP) of noble gases, and brute force methods enable significant signal enhancements of low gyromagnetic ratio nuclei such as 13C, 15N, 29Si, 129Xe, among others, in a range of endogenous or exogenous metabolites. Quantitative hyperpolarized MRI has been deployed to yield an improved understanding of the activities of endogenous enzymes, membrane transporters, and perfusion, as well as their modulation by disease processes or therapeutics. Hyperpolarization methods are finding a range of applications in oncology, cardiology, pulmonary imaging, abdominal imaging, and neuroimaging.