T 2 relaxation times of 13 C metabolites in a rat hepatocellular carcinoma model measured in vivo using 13 C‐MRS of hyperpolarized [1‐ 13 C]pyruvate

A single‐voxel Carr‐Purcell‐Meibloom‐Gill sequence was developed to measure localized T 2 relaxation times of 13 C‐labeled metabolites in vivo for the first time. Following hyperpolarized [1‐ 13 C]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 T 2 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 13 C signal than normal livers ( p  < 0.006). The intra‐ and inter‐subject variations of the alanine T 2 relaxation time were 11% and 13%, respectively. The intra‐ and inter‐subject variations of the lactate T 2 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‐ 13 C]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.