Proton T 2 measurement and quantification of lactate in brain tumors by MRS at 3 Tesla in vivo

Purpose To evaluate the T 2 relaxation time of lactate (Lac) in brain tumors and the correlation of the T 2 and concentration with tumor grades. Methods Eight pairs of the subecho time sets of point‐resolved spectroscopy were selected between 58 and 268 ms, with numerical and phantom analyses, for Lac T 2 measurement. In vivo spectra were acquired from 24 subjects with gliomas (13 low grade and 11 high grade) and analyzed with LCModel using numerically‐calculated basis spectra. The metabolite T 2 relaxation time was obtained from monoexponential fitting of the multi‐echo time (TE) signal estimates versus TE. The metabolite concentration was estimated from the zero‐TE extrapolation of the T 2 fits. Results The Lac T 2 was estimated to be approximately 240 ms, without a significant difference between low and high grade tumors. The Lac concentration was estimated to be 4.1 ± 3.4 and 7.0 ± 4.7 mM for low and high grades respectively, but the difference was not significant. Conclusion The Lac T 2 was similar among gliomas regardless of their tumor grades. This suggests that the T 2 value from this study may be applicable to obtain the T 2 relaxation‐free estimates of Lac in a subset of brain tumors. Magn Reson Med 73:2094–2099, 2015. © 2014 Wiley Periodicals, Inc.