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

Purpose To evaluate the T sub(2) relaxation time of lactate (Lac) in brain tumors and the correlation of the T sub(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 sub(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 sub(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 sub(2) fits. Results The Lac T sub(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 plus or minus 3.4 and 7.0 plus or minus 4.7 mM for low and high grades respectively, but the difference was not significant. Conclusion The Lac T sub(2) was similar among gliomas regardless of their tumor grades. This suggests that the T sub(2) value from this study may be applicable to obtain the T sub(2) relaxation-free estimates of Lac in a subset of brain tumors. Magn Reson Med 73:2094-2099, 2015.