Virtual special issue: Magnetic resonance at low fields

NMR Spin-Lock Induced Crossing (SLIC) dispersion and long-lived spin states of gaseous propane at low magnetic field (0.05 T)

“…1 The recent boost of interest in low-field NMR/MRI can be explained by three primary reasons. First, several hyperpolarization techniques rapidly emerged, which enhance NMR signals by orders of magnitude, 2 thereby significantly improving the signal-to-noise ratio (SNR).…”

“…19 While any hyperpolarization technique can be used in the context of low-field NMR/MRI, less expensive and more high-throughput parahydrogen-based hyperpolarization techniques, such as parahydrogen-induced polarization (PHIP) 20-22 and signal amplification by reversible exchange (SABRE), 23-28 are naturally more suited to go hand-in-hand with an inexpensive low-field MR modality rather than the more expensive (millions of dollars) and low-throughput technique of dissolution dynamic nuclear polarization (d-DNP), 29-30 currently the leading hyperpolarization technology. 1, 31-32 It is also worth emphasizing that the maximum polarization obtainable by d-DNP depends strongly on the applied magnetic field and spin temperature (since it is a phenomenon of polarization transfer from electrons to nuclei), whereas for PHIP and SABRE the maximum polarization is independent of these parameters. Furthermore, in addition to biomedical applications, the combination of hyperpolarization and low-field detection can be also potentially useful for spectroscopic and imaging analysis of industrial-scale processes, where overpopulated pseudo-singlet spin states are conveniently created using chemical reactions involving parahydrogen.…”

2D Mapping of NMR Signal Enhancement and Relaxation for Heterogeneously Hyperpolarized Propane Gas

“…Hyperpolarization techniques are revolutionizing the field of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) because they allow significant increase of nuclear spin polarization by several orders of magnitude. − This immense polarization gain renders concomitant gains in the NMR/MRI detection sensitivity by 4–8 orders of magnitude − depending on the static magnetic field of the detector, thus enabling new applications in various fields including biomedicine. Biomedical applications of hyperpolarization are the main driving forces for the fundamental and applied scientific development of hyperpolarization methods. ,− Hyperpolarized (HP) compounds are prepared exogenously, and once administered in vivo (via intravenous injection or inhalation), they act as contrast agents for probing metabolism and organ function.…”

High-resolution hyperpolarized in vivo metabolic 13C spectroscopy at low magnetic field (48.7 mT) following murine tail-vein injection

“…Hyperpolarization techniques, however, produce spin polarization independent of the readout magnet, and therefore, they provide freedom to select a magnetic field strength, and correspondingly a detection frequency, optimized to the nucleus observed [7, 8] and the dielectric properties of the sample [9–11]. Of particular interest is the quickly developing frontier of low-field magnetic resonance (NMR) and imaging (MRI) [12–14], due to its ability to strongly complement the study of hyperpolarized (HP) nuclei, and its potential for application in areas of study including heteronuclear spin-labeled metabolites [15, 16] or other contrast agents [17–22] at low concentrations.…”

“…Fourth, experimental validation of the theoretical equations for low-field NMR and MRI [12, 13] sensitivity for hyperpolarized states has favorably corroborated the weak frequency dependence of hyperpolarized state detection, where these theories indicate the potential for approaching or even exceeding the sensitivity of high-field NMR/MRI [12, 13]. Lastly, utilization of low-field magnets provides significantly less expensive purchasing and maintenance costs, which can pair favorably with lower-cost methods of producing hyperpolarized spin states such as Spin Exchange Optical Pumping (SEOP) primarily focused on 3 He and 129 Xe [1, 38–42] or the high-throughput parahydrogen-based methods [5, 14, 43] including parahydrogen-induced polarization (PHIP) [44–46] and signal amplification by reversible exchange (SABRE) [47–51]. …”