Long and short echo time proton magnetic resonance spectroscopic Imaging of the healthy aging brain

Purpose: To investigate the relationship between subject age and white matter brain metabolite concentrations and R-2 relaxation rates in a cross-sectional study of human brain. Materials and Methods: Long- and short-echo proton spectroscopic imaging were used to investigate concentrations and R-2 relaxation rates of N-acetyl aspartate (NAA) + N-acetyl aspartyl glutamate (NAAG), choline (Cho), creatine (Cr). and myoinositol (mI) in the white matter of the centrum semiovale of 106 healthy volunteers aged 50 - 90 years: usable data were obtained from 79 subjects. A major aim was to identify which parameters were most sensitive to changes with age. Spectra were analyzed using the LCModel method. Results: The apparent R-2 of NAA and the LCModel concentration of Cr at short echo time were significantly correlated with age after multiplicity correction. Large lipid resonances were observed in the brain midline of some subjects, the incidence increasing significantly with age. We believe this to result from lipid deposits in the falx cerebri. Conclusion: Since only short-echo spectroscopy showed a robust relationship between Cr and subject age, and detects more metabolites than long echo time, we conclude that short-echo is superior to long-echo for future aging studies. Future studies could usefully determine whether the Cr - age relationship is due to changes in concentration, TI, or both.