Signal amplification by reversible
exchange (SABRE) of a substrate
and parahydrogen at a catalytic center promises to
overcome the inherent insensitivity of magnetic resonance. In order
to apply the new approach to biomedical applications, there is a need
to develop experimental equipment, in situ quantification
methods, and a biocompatible solvent. We present results detailing
a low-field SABRE polarizer which provides well-controlled experimental
conditions, defined spins manipulations, and which allows in situ detection of thermally polarized and hyperpolarized
samples. We introduce a method for absolute quantification of hyperpolarization
yield in situ by means of a thermally polarized reference.
A maximum signal-to-noise ratio of ∼103 for 148
μmol of substance, a signal enhancement of 106 with
respect to polarization transfer field of SABRE, or an absolute 1H-polarization level of ≈10–2 is
achieved. In an important step toward biomedical application, we demonstrate 1H in situ NMR as well as 1H and 13C high-field MRI using hyperpolarized pyridine (d3) and 13C nicotinamide in pure and 11% ethanol
in aqueous solution. Further increase of hyperpolarization yield,
implications of in situ detection, and in
vivo application are discussed.
Direct detection of thermal and hyperpolarized (1)H-MR signal in a single acquisition and accurate spin manipulations at 1.8 and 5.5 mT were successfully demonstrated.
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