Regional apparent metabolite concentrations in young adult brain measured by ¹H MR spectroscopy at 3 Tesla

Abstract

Purpose: To quantify and examine the distribution of brain metabolites in normal young adults using single voxel MR spectroscopy at 3 Tesla (T). Materials and Methods:Short-echo time single-voxel PRESS technique was used to measure the apparent concentration of five metabolites at nine locations in the brains of young adults. Concentrations were estimated by means of an automated fitting method (LCModel) with reference to an unsuppressed water signal and were corrected for T 1 relaxation, T 2 relaxation, and cerebrospinal fluid partial volume. Analysis of variance with Tukey post hoc test was used to evaluate regional variations.Results: Statistically significant differences in regional concentrations were detected for each of the metabolites. The number of significant differences was greatest for total choline, whereas myo-inositol and the sum of glutamine and glutamate had the fewest. Magnitude of variation was greatest for total choline and least for the sum of N-acetyl aspartate and N-acetylaspartylglutamate. Conclusion:In agreement with previous studies at other field strengths, we found heterogeneous distribution of the major spectroscopically measurable brain metabolites. Although the most distinct differences are between tissue types, there is appreciable variation within a tissue type at different locations. The spectra and metabolite concentrations presented should provide a useful reference for both clinical and research MR spectroscopy studies performed at 3T. PROTON MR SPECTROSCOPY (MRS) of the brain is a useful technique for evaluating several neurological and psychiatric diseases (1). For clinicians interpreting spectra from individual patients, it is important to have knowledge of the normal range of spectral patterns from different brain regions, including how the spectra may depend on the patient's age, and on the spectroscopic technique used. While normal regional and age-related spectral variations have been reported previously at field strengths of 1T (2-5), 2T (6 -8), and 4T (9,10), to the best of our knowledge, there have been no reports using 3T scanners. Because use of 3T scanners is increasing for neuroimaging and spectroscopy in clinical practice, there is, therefore, a need for normative 3T data for comparison with patient studies. Also, even when results from all field strengths are taken together, there have been relatively few quantitative reports of normal values; therefore, expansion of coverage of different brain regions and confirmation of previously reported values is desirable.The purpose of this study was to establish normative spectroscopic data at 3T, from a variety of regions often involved in brain pathology, using commonly available methodology (single voxel PRESS localization at short echo time, with analysis using the LCModel software (11)). Because MRS-measurable metabolic asymmetry in the human brain is minimal (12), unilateral measurements from multiple different anatomical regions were measured, rather than bilateral measurements in fewer structures. Quantitative ...

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“…However, they found no statistically significant variations along the white or grey matter itself (Baker et al 2008). …”

“…Spatial distribution of glutamate and glutamine in the brain measured at a 3 T magnetic field (Baker et al 2008) is shown in Table 2. Even though it was possible to distinguish between glutamate and glutamine at 3 T, the work suggested that it was still more precise to mention the summary value of Glx.…”

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