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Abstract Imaging of gases is a major challenge for any modality including MRI. NMR and MRI signals are directly proportional to the nuclear spin density and the degree of alignment of nuclear spins with applied static magnetic field, which is called nuclear spin polarization. The level of nuclear spin polarization is typically very low, i.e., one hundred thousandth of the potential maximum at 1.5 T and a physiologically relevant temperature. As a result, MRI typically focusses on imaging highly concentrated tissue water. Hyperpolarization methods transiently increase nuclear spin polarizations up to unity, yielding corresponding gains in MRI signal level of several orders of magnitude that enable the 3D imaging of dilute biomolecules including gases. Parahydrogen‐induced polarization is a fast, highly scalable, and low‐cost hyperpolarization technique. The focus of this Minireview is to highlight selected advances in the field of parahydrogen‐induced polarization for the production of hyperpolarized compounds, which can be potentially employed as inhalable contrast agents.
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Rapid Hyperpolarization and Purification of the Metabolite Fumarate in Aqueous Solution
Hyperpolarized fumarate is a promising agent for carbon-13 magnetic resonance metabolic imaging of cellular necrosis. Molecular imaging applications require nuclear hyperpolarization to attain sufficient signal strength. Dissolution dynamic nuclear polarization is the current state-of-the-art methodology for hyperpolarizing fumarate, but this is expensive and relatively slow. Alternatively, this important biomolecule can be hyperpolarized in a cheap and convenient manner using parahydrogen-induced polarization. However, this process requires a chemical reaction, and the resulting hyperpolarized fumarate solutions are contaminated with the catalyst, unreacted reagents, and reaction side product molecules, and are hence unsuitable for use in vivo. In this work, we show that the hyperpolarized fumarate can be purified from these contaminants by acid precipitation as a pure solid, and later redissolved at a chosen concentration in a clean aqueous solvent. Significant advances in the reaction conditions and reactor equipment allow us to form hyperpolarized fumarate at a concentration of several hundred millimolar, at 13C polarization levels of 30-45%.
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- Award ID(s):
- 1709944
- PAR ID:
- 10202975
- Date Published:
- Journal Name:
- ChemRxiv
- ISSN:
- 2573-2293
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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