, Volume 20, Issue 3, pp 143-155,
Open Access This content is freely available online to anyone, anywhere at any time.
Date: 30 Jun 2007

Estimation of metabolite T 1 relaxation times using tissue specific analysis, signal averaging and bootstrapping from magnetic resonance spectroscopic imaging data

Abstract

Object A novel method of estimating metabolite T 1 relaxation times using MR spectroscopic imaging (MRSI) is proposed. As opposed to conventional single-voxel metabolite T 1 estimation methods, this method investigates regional and gray matter (GM)/white matter (WM) differences in metabolite T 1 by taking advantage of the spatial distribution information provided by MRSI.

Material and methods The method, validated by Monte Carlo studies, involves a voxel averaging to preserve the GM/WM distribution, a non-linear least squares fit of the metabolite T 1 and an estimation of its standard error by bootstrapping. It was applied in vivo to estimate the T 1 of N-acetyl compounds (NAA), choline, creatine and myo-inositol in eight normal volunteers, at 1.5 T, using a short echo time 2D-MRSI slice located above the ventricles.

Results WM-T 1,NAA was significantly (P < 0.05) longer in anterior regions compared to posterior regions of the brain. The anterior region showed a trend of a longer WM T 1 compared to GM for NAA, creatine and myo-Inositol. Lastly, accounting for the bootstrapped standard error estimate in a group mean T 1 calculation yielded a more accurate T 1 estimation.

Conclusion The method successfully measured in vivo metabolite T 1 using MRSI and can now be applied to diseased brain.