科研之友
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摘要
Hyperpolarized C-13 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-C-13] Pyr in any hyperpolarized [1-C-13] 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.
- 出版日期2017-2
