T2 measurement and quantification of glutamate in human brain in vivo

Changho Choi, Nicholas J. Coupland, Paramjit P. Bhardwaj, Sanjay Kalra, Colin A. Casault, Kim Reid, Peter S. Allen

Research output: Contribution to journalArticlepeer-review

63 Scopus citations

Abstract

The proton NMR transverse relaxation time T2 of glutamate (Glu) in human brain was measured by means of spectrally selective refocusing at 3.0 T in vivo. An 81.4-ms-long dual-band Gaussian 180° RF pulse, designed for refocusing at 2.35 and 3.03 ppm, was employed within point-resolved spectroscopy (PRESS) to generate the Glu C4-proton target multiplet and the total creatine (tCr) singlet. Six optimal echo times (TEs) between 128 and 380 ms were selected from numerical analysis of the filtering performance for effective detection of the Glu signal with minimal contamination from glutamine (Gln), N-acetylaspartate (NAA), and glutathione (GSH). The magnetization of Glu and tCr was extracted from spectral fitting of experimental and calculated spectra. Apparent T2 values of Glu and tCr were estimated as 201 ± 18 and 164 ± 12 ms for the medial prefrontal (PF) cortex, and 198 ± 22 and 169 ± 15 ms (mean ± SD, N = 5) for the left frontal (LF) cortex, respectively. With water segmentation data, the magnetization values of Glu and tCr of the two adjacent voxels, calculated from the T2 values and spectra following the thermal equilibrium magnetization, were combined to give the Glu and tCr concentrations as 10.37 ± 1.06 and 8.87 ± 0.56 mM for gray matter (GM), and 5.06 ± 0.57 and 5.16 ± 0.45 mM (mean ± SD, N = 5) for white matter (WM), respectively.

Original languageEnglish (US)
Pages (from-to)971-977
Number of pages7
JournalMagnetic resonance in medicine
Volume56
Issue number5
DOIs
StatePublished - Nov 1 2006

Keywords

  • Double-banded 180° RF pulse
  • Glutamate
  • Gray matter
  • Human brain
  • Prefrontal
  • Proton MRS
  • Spectrally-selective refocusing
  • Transverse relaxation time T
  • White matter

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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