Interindividual reproducibility of glutamate quantification using 1.5-T proton magnetic resonance spectroscopy

The goal of this study was to measure the interindividual reproducibility of glutamate quantification in 1.5-T ¹H MRS of human brains. To determine the effective echo time (TE) for glutamate quantification, spectra from a phantom and 12 participants were obtained with TE = 30, 35, 40, and 144 ms (repetition time (TR) = 2000 ms and volume of interest - 4 cm³). The average Cramér-Rao lower bounds for glutamate quantification using LCModel was lowest in two experiments when TE = 40 ms. Twenty-one subjects participated in experiments that measured interindividual reproducibility of glutamate quantification. Spectra were acquired with TR = 6000 ms and TE = 40 ms. Results showed that the coefficients of variance were 11.0 and 13.1% in the anterior cingulate cortex and insula, respectively. This suggests that glutamate can be reproducibly measured from 1.5-T ¹H MRS with long TR, effective TE, and the LCModel.