Spin Hyperpolarization in Modern Magnetic Resonance

Abstract

Magnetic resonance techniques are successfully utilized in a broad range of scientific disciplines and in various practical applications, with medical magnetic resonance imaging being the most widely known example. Currently, both fundamental and applied magnetic resonance are enjoying a major boost owing to the rapidly developing field of spin hyperpolarization. Hyperpolarization techniques are able to enhance signal intensities in magnetic resonance by several orders of magnitude, and thus to largely overcome its major disadvantage of relatively low sensitivity. This provides new impetus for existing applications of magnetic resonance and opens the gates to exciting new possibilities. In this review, we provide a unified picture of the many methods and techniques that fall under the umbrella term "hyperpolarization" but are currently seldom perceived as integral parts of the same field. Specifically, before delving into the individual techniques, we provide a detailed analysis of the underlying principles of spin hyperpolarization. We attempt to uncover and classify the origins of hyperpolarization, to establish its sources and the specific mechanisms that enable the flow of polarization from a source to the target spins. We then give a more detailed analysis of individual hyperpolarization techniques: the mechanisms by which they work, fundamental and technical requirements, characteristic applications, unresolved issues, and possible future directions. We are seeing a continuous growth of activity in the field of spin hyperpolarization, and we expect the field to flourish as new and improved hyperpolarization techniques are implemented. Some key areas for development are in prolonging polarization lifetimes, making hyperpolarization techniques more generally applicable to chemical/biological systems, reducing the technical and equipment requirements, and creating more efficient excitation and detection schemes. We hope this review will facilitate the sharing of knowledge between subfields within the broad topic of hyperpolarization, to help overcome existing challenges in magnetic resonance and enable novel applications.

Efficient SABRE-SHEATH Hyperpolarization of Potent Branched-Chain-Amino-Acid Metabolic Probe [1-13C]ketoisocaproate

“…As a consequence, only compounds at a high physiological concentration such as water protons (ca. 100 M) [ 1 ] can be detected easily. Imaging of lower-concentration species is challenging, and only possible at the expense of spatial and temporal resolution [ 2 ].…”

“…NMR hyperpolarization enables transient P increases, up to order unity [ 1 , 3 , 4 , 5 ] (i.e., 100%). Hyperpolarized (HP) exogenous contrast agents can be administered via inhalation or injection [ 1 , 6 , 7 , 8 , 9 , 10 , 11 ].…”

“…NMR hyperpolarization enables transient P increases, up to order unity [ 1 , 3 , 4 , 5 ] (i.e., 100%). Hyperpolarized (HP) exogenous contrast agents can be administered via inhalation or injection [ 1 , 6 , 7 , 8 , 9 , 10 , 11 ]. The hyperpolarized signals are increased by 4–5 orders of magnitude [ 12 ], and enable the use of a relatively small bolus of HP contrast agent [ 13 , 14 ] for enhanced MRI.…”

Facile hyperpolarization chemistry for molecular imaging and metabolic tracking of [1-13C]pyruvate in vivo

“…To address the sensitivity challenge faced by MR approaches, hyperpolarization methods have been developed to align much larger fractions of nuclear spins and improve the sensitivity limits of NMR and MRI by several orders of magnitude. [34][35][36][37][38][39] Indeed, the first hyperpolarized (HP) contrast agent ( 129 Xe gas) [40][41][42][43][44] has been FDA approved for ventilation lung imaging. Other HP molecular probes are also emerging for molecular imaging, including [1-13 C]pyruvate.…”

The solid-state DNP effect in liquids

“…The last two decades have witnessed an overarching development in nuclear hyperpolarization techniques across the entire spectrum of mechanisms, from the classical Overhauser and solid-state effects to (photo)chemically-induced and parahydrogenbased polarization (Eills et al, 2023). While the majority of the reported applications have relied on polarization transfer in the solid state at cryogenic temperatures (Ni et al, 2013;Pinon et al, 2021), transfer in the liquid state at elevated (room or physiological) temperatures has also been actively explored (Prisner et al, 2016;Denysenkov et al, 2022).…”