T2 Relaxation Times of 13C Metabolites in a Rat Hepatocellular Carcinoma Model Measured in Vivo Using 13C-MRS of Hyperpolarized [1-13C]Pyruvate

Abstract

A single-voxel Carr-Purcell-Meibloom-Gill sequence was developed to measure localized T₂ relaxation times of ¹³C-labeled metabolites in vivo for the first time. Following hyperpolarized [1-¹³C]pyruvate injections, pyruvate and its metabolic products, alanine and lactate, were observed in the liver of five rats with hepatocellular carcinoma and five healthy control rats. The T₂ relaxation times of alanine and lactate were both significantly longer in HCC tumors than in normal livers (p < 0.002). The HCC tumors also showed significantly higher alanine signal relative to the total ¹³C signal than normal livers (p < 0.006). The intra- and inter-subject variations of the alanine T₂ relaxation time were 11% and 13%, respectively. The intra- and inter-subject variations of the lactate T₂ relaxation time were 6% and 7%, respectively. The intra-subject variability of alanine to total carbon ratio was 16% and the inter-subject variability 28%. The intra-subject variability of lactate to total carbon ratio was 14% and the inter-subject variability 20%. The study results show that the signal level and relaxivity of [1-¹³C]alanine may be promising biomarkers for HCC tumors. Its diagnostic values in HCC staging and treatment monitoring are yet to be explored. Copyright © 2010 John Wiley & Sons, Ltd.