A hyperpolarized equilibrium for magnetic resonance

Abstract

Nuclear magnetic resonance spectroscopy and imaging (MRI) play an indispensable role in science and healthcare but use only a tiny fraction of their potential. No more than ≈10 p.p.m. of all 1H nuclei are effectively detected in a 3-Tesla clinical MRI system. Thus, a vast array of new applications lays dormant, awaiting improved sensitivity. Here we demonstrate the continuous polarization of small molecules in solution to a level that cannot be achieved in a viable magnet. The magnetization does not decay and is effectively reinitialized within seconds after being measured. This effect depends on the long-lived, entangled spin-order of parahydrogen and an exchange reaction in a low magnetic field of 10−3 Tesla. We demonstrate the potential of this method by fast MRI and envision the catalysis of new applications such as cancer screening or indeed low-field MRI for routine use and remote application.

Delivering strong 1 H nuclear hyperpolarization levels and long magnetic lifetimes through signal amplification by reversible exchange

“…This simple process takes just a few seconds and is illustrated in Fig. 1 (24). Furthermore, the agents' hyperpolarization level can be maintained in low field when under p-H 2 because it can be continually repolarized (24,25).…”

“…1 (24). Furthermore, the agents' hyperpolarization level can be maintained in low field when under p-H 2 because it can be continually repolarized (24,25). Consequently we predict that the future optimization of this method will be easier than that of many other approaches if we can deliver agents with high signal strengths and appropriately long-lived magnetization.…”

ParaHydrogen Induced Polarization of 13C carboxylate resonance in acetate and pyruvate

“…As far as PHIP is concerned, efficient polarization transfer from parahydrogen spin order to 13 C longitudinal magnetization of carbonyl groups can be achieved by the addition of the para-H 2 molecule to a double or a triple bond adjacent to the carbonyl group 23 . The amount of polarization transferred from parahydrogen protons (A and A 0 ) to heteronuclear resonances (X) (that is, 13 C) depends on the coupling asymmetry of the two parahydrogen protons with the X nucleus (J AX -J A 0 X /2*J AA 0 ) 27,28 .…”

“…An attempt to tackle the major limitations of PHIP has been pursued with the recently introduced signal amplification by reversible exchange method [21][22][23] . With this approach, parahydrogen protons are not added to the substrate but the hyperpolarization transfer takes place on a transient adduct formed by the substrate, parahydrogen and the organometallic complex.…”

Measuring molecular parity nonconservation using nuclear-magnetic-resonance spectroscopy

“…Another potential hyperpolarization modality is parahydrogen-induced polarization (PHIP) [42], which can provide similar enhancements to DNP. Nonhydrogenative PHIP (also called signal amplification by reversible exchange, or SABRE) [43] has the additional advantage of providing a continuously hyperpolarized sample [44], and has been demonstrated for relatively heavy nuclei like 119 Sn [45]. It would also be interesting to explore whether coherent experiments, like the NMR "RASER" of Ref.…”