Quantitative analysis of short echo time H-1-MRSI of cerebral gray and white matter

Quantitative analysis of H-1-magnetic resonance spectroscopic imaging (MRSI ) data was developed using the user-independent spectral analysis routine L CModel. Tissue segmentation was performed using statistical parametric mapp ing software (SPM 96), and the results were used to correct for cerebrospin al fluid contamination. A correction was developed for the imperfections in the spectroscopic excitation profile in order to improve the uniformity of metabolite images. After validation in phantoms, these techniques were app lied to study differences in metabolite concentrations between gray and whi te matter in normal volunteers (n = 13), A positive correlation was found b etween concentration and gray matter content for most metabolites studied. The estimated ratios of metabolite concentration in gray vs. white matter w ere: N-acetyl aspartate + ;N-acetyl aspartyl glutamate (NAc)= 1.16 +/- 0.11 ; creatine = 1.7 +/- 0.3; glutamate + glutamine = 2.4 +/- 0.5; myo-inositol = 1.6 +/- 0.3; choline = 0.9 +/- 0.2. The ratio of NAc/Cr was negatively c orrelated with gray matter content: gray/white = 0.69 +/- 0.08. These metho ds will be useful in the evaluation of metabolite concentrations in MRSI vo xels with mixed tissue composition in patient groups. (C) 2000 Wiley-Liss, Inc.