Diffusion-Weighted Spectroscopy: A Novel Approach to Determine Macromolecule Resonances in Short-Echo Time 1H-MRS

Quantification of short-echo time proton magnetic resonance spectroscopy results in >18 metabolite concentrations (neurochemical profile). Their quantification accuracy depends on the assessment of the contribution of macromolecule (MM) resonances, previously experimentally achieved by exploiting the several fold difference in T-1. To minimize effects of hetero-geneities in metabolites T-1, the aim of the study was to assess MM signal contributions by combining inversion recovery (IR) and diffusion-weighted proton spectroscopy at high-magnetic field (14.1 T) and short echo time (=8 msec) in the rat brain. IR combined with diffusion weighting experiments (with delta/Delta = 1.5/200 msec and b-value = 11.8 msec/mu m(2)) showed that the metabolite nulled spectrum (inversion time = 740 msec) was affected by residuals attributed to creatine, inositol, taurine, choline, N-acetylaspartate as well as glutamine and glutamate. While the metabolite residuals were significantly attenuated by 50%, the MM signals were almost not affected (<8%). The combination of metabolite-nulled IR spectra with diffusion weighting allows a specific characterization of MM resonances with minimal metabolite signal contributions and is expected to lead to a quantification of the neurochemical profile. Med 64:939-946, 2010. (C) 2010 Wiley-Liss, Inc.