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Doublet asymmetry for estimating polarization in hyperpolarized 13 C–pyruvate studies
Author(s) -
Datta Keshav,
Spielman Daniel M.
Publication year - 2017
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3670
Subject(s) - asymmetry , chemistry , polarization (electrochemistry) , anisotropy , nuclear magnetic resonance , dipole , physics , analytical chemistry (journal) , optics , organic chemistry , chromatography , quantum mechanics
Hyperpolarized 13 C MRS allows in vivo interrogation of key metabolic pathways, with pyruvate (Pyr) the substrate of choice for current clinical studies. Knowledge of the liquid‐state polarization is needed for full quantitation, and asymmetry of the C 2 doublet, arising from 1% naturally abundant [1,2‐ 13 C]Pyr in any hyperpolarized [1‐ 13 C]Pyr sample, has been suggested as a direct measure of in vivo C 1 polarization via the use of an in vitro calibration curve. Here we show that different polarization levels can yield the same C 2 ‐doublet asymmetry, thus limiting the utility of this metric for quantitation. Furthermore, although the time evolution of doublet asymmetry is poorly modeled using the expected dominant relaxation mechanisms of carbon‐proton dipolar coupling and chemical shift anisotropy, the inclusion of a C‐C dipolar coupling term can explain the observed initial evolution of the C 2 doublet asymmetry beyond its expected thermal equilibrium value.