Proton T(1) relaxation times of metabolites in human occipital white and gray matter at 7 T
Proton T(1) relaxation times of metabolites in the human brain have not previously been published at 7 T. In this study, T(1) values of CH(3) and CH(2) group of N-acetylaspartate and total creatine as well as nine other brain metabolites were measured in occipital white matter and gray matter at 7 T using an inversion-recovery technique combined with a newly implemented semi-adiabatic spin-echo full-intensity acquired localized spectroscopy sequence (echo time = 12 ms). The mean T(1) values of metabolites in occipital white matter and gray matter ranged from 0.9 to 2.2 s. Among them, the T(1) of glutathione, scyllo-inositol, taurine, phosphorylethanolamine, and N-acetylaspartylglutamate were determined for the first time in the human brain. Significant differences in T(1) between white matter and gray matter were found for water (-28%), total choline (-14%), N-acetylaspartylglutamate (-29%), N-acetylaspartate (+4%), and glutamate (+8%). An increasing trend in T(1) was observed when compared with previously reported values of N-acetylaspartate (CH(3) ), total creatine (CH(3) ), and total choline at 3 T. However, for N-acetylaspartate (CH(3) ), total creatine, and total choline, no substantial differences compared to previously reported values at 9.4 T were discernible. The T(1) values reported here will be useful for the quantification of metabolites and signal-to-noise optimization in human brain at 7 T. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.