Quantitative T1ρ NMR spectroscopy of rat cerebral metabolites in vivo:: Effects of global ischemial

The NMR relaxation times (T-1rho, T-2, and T-1) of water, N-acety-laspartate (NAA), creatine (Cr), choline-containing compounds (Cho), and lactate (Lac) were quantified in rat brain at 4.7 T. In control animals, the cerebral T, figures, as determined with a spin-lock field of 1.0 G, were 575 +/- 30 ms, 380 +/- 19 ms, 705 +/- 53 ms, and 90 +/- 1 ms for NAA, Cr, Cho, and water, respectively. The T-1rho figures were 62-103% longer than their respective T-2 values determined by a multiecho method. In global (ischemic) ischernia, T-1rho, of NAA declined by 34%, that of Cr and Cho did not change, and that of water increased by 10%. The T-1rho of lactate in ischemic brain was 367 +/- 44 ms. Similar patterns of changes were observed in the multiecho T-2 of these cerebral metabolites. The T-1 of water and NAA changed in a fashion similar to that of T-1rho and T-2. These results show differential responses in metabolite and water T-1rho relaxation times following ischernia, and indicate that metabolite T-1rho and T-2 relaxation times behave similarly in the ischemic brain. The contributions of dipolar and nondipolar effects on T-1rho relaxation in vivo are discussed in this work. Magn Reson Med 51:875-880, 2004. (C) 2004 Wiley-Liss, Inc.