Proton T2 relaxation study of water, N-acetylaspartate, and creatine in human brain using Hahn and Carr-Purcell spin echoes at 4T and 7T

Carr-Purcell and Hahn spin-echo (SE) measurements were used to estimate the apparent transverse relaxation time constant (T-2(dagger)) of water and metabolites in human brain at 4T and 7T. A significant reduction in the T-2(dagger) values of proton resonances (water, N-acetylaspartate, and creatine/phosphocreatine) was observed with increasing magnetic field strength and was attributed mainly to increased dynamic dephasing due to increased local susceptibility gradients. At high field, signal loss resulting from T-2(dagger) decay can be substantially reduced using a Carr-Purcell-type SE sequence. (C) 2002 Wiley-Liss, Inc.