title: Doublet asymmetry for estimating polarization in hyperpolarized13C-pyruvate studies.
abstract: Hyperpolarized13C 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 C2doublet, arising from 1% naturally abundant [1,2-13C]Pyr in any hyperpolarized [1-13C]Pyr sample, has been suggested as a direct measure of in vivo C1polarization via the use of an in vitro calibration curve. Here we show that different polarization levels can yield the same C2-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 C2doublet asymmetry beyond its expected thermal equilibrium value.
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, USA.|Department of Radiology, Stanford University, Stanford, California, USA.
authors.forename: Keshav
authors.initials: K
authors.lastname: Datta
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, USA.|Department of Radiology, Stanford University, Stanford, California, USA.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Spielman
mesh_terms: D000465:Algorithms; D066241:Carbon-13 Magnetic Resonance Spectroscopy / Q000379:methods*; D003198:Computer Simulation; D008956:Models, Chemical; D057054:Molecular Imaging / Q000379:methods; D019289:Pyruvic Acid / Q000032:analysis* / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
chemical_list: D019289:Pyruvic Acid
keywords: MRS; asymmetry; carbon-13; doublet; hyperpolarized; liquid-state polarization; polarization measurement; pyruvate