In vivo 13carbon metabolic imaging at 3T with hyperpolarized 13C-1-pyruvate

Abstract

We present for the first time dynamic spectra and spectroscopic images acquired in normal rats at 3T following the injection of 13C-1- pyruvate that was hyperpolarized by the dynamic nuclear polarization (DNP) method. Spectroscopic sampling was optimized for signal-to-noise ratio (SNR) and for spectral resolution of 13C-1-pyruvate and its metabolic products 13C-1-alanine, 13C-1-lactate, and 13C- bicarbonate. Dynamic spectra in rats were collected with a temporal resolution of 3 s from a 90-mm axial slab using a dual 1H-13C quadrature bird-cage coil to observe the combined effects of metabolism, flow, and T1 relaxation. In separate experiments, spectroscopic imaging data were obtained during a 17-s acquisition of a 20-mm axial slice centered on the rat kidney region to provide information on the spatial distribution of the metabolites. Conversion of pyruvate to lactate, alanine, and bicarbonate occurred within a minute of injection. Alanine was observed primarily in skeletal muscle and liver, while pyruvate, lactate, and bicarbonate concentrations were relatively high in the vasculature and kidneys. In contrast to earlier work at 1.5T, bicarbonate was routinely observed in skeletal muscle as well as the kidney and vasculature. © 2007 Wiley-Liss, Inc.