T2relaxation times of13C metabolites in a rat hepatocellular carcinoma model measuredin vivousing13C-MRS of hyperpolarized [1-13C]pyruvate

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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.