Metabolite T 1 relaxation times differ across the adult lifespan

Abstract Purpose To investigate the age-dependence of metabolite T 1 relaxation times at 3T in both gray- and white-matter-rich voxels. Methods This manuscript analyzes publicly available metabolite and metabolite-nulled (single inversion recovery TI = 600 ms) spectra acquired at 3T using PRESS localization. Voxels were placed in posterior cingulate cortex and centrum semiovale in 102 healthy volunteers across 5 decades of life (20s to 60s). All spectra were analyzed in Osprey v2.4.0. To estimate T 1 relaxation times for tNAA 2.0 and tCr 3.0 , the ratio of modeled metabolite residual amplitudes in the metabolite-nulled spectrum to the full metabolite signal was calculated using the single inversion recovery signal equation. Correlations between T 1 and subject age were evaluated. Results Spearman correlations revealed that estimated T 1 relaxation times of tNAA 2.0 (r s = −0.43; p < 0.001) and tCr 3.0 (r s = −0.23; p = 0.021) decreased significantly with age in white-matter-rich CSO, and less steeply (and not significantly) for tNAA 2.0 (r s = −0.15; p = 0.136) and tCr 3.0 (r s = −0.10; p = 0.319) in gray-matter-rich PCC. Conclusion The analysis harnessed a large publicly available cross-sectional dataset to test an important hypothesis, that metabolite T 1 relaxation times change with age. This preliminary study stresses the importance of further work to measure age-normed metabolite T 1 relaxation times for accurate quantification of metabolite levels in studies of aging.