Rationale and objectives: This study compared metabolic differences in the frontal brain of depressed patients versus age- and sex-matched controls using proton magnetic resonance spectroscopy and absolute quantification of metabolites (NAA, Cr, Cho, mI) at 3 Tesla.
Methods: Short-echo-time stimulated echo acquisition mode (TE/TM/TR=20/30/6000 milliseconds) was applied in the prefrontal region of 17 depressed patients and 17 age- and sex-matched controls. Metabolic ratios, ie, N-acetyl-aspartate/creatine (Cr), choline/Cr, and myo-inositol/Cr, and absolute concentrations (using internal water as a reference together with LCModel-based spectra fitting) were calculated and compared between groups and published reference data.
Results: Metabolic ratios showed significantly lower N-acetyl-aspartate/Cr (P = 0.016/0.006, left/right), choline/Cr (P = n.s./0.016), and myo-inositol/Cr (P = 0.022/0.026) for depressive patients versus controls. However, depressive patients showed significantly higher absolute concentrations of Cr (P = 0.017/0.0004) compared with controls with no differences in all other metabolites estimated.
Conclusions: The authors demonstrate that absolute quantification of metabolite concentration is essential in properly identifying pathologic differences of brain metabolites in depression.