Simple approach of combined passive and active shimming for in vivo MR spectroscopy of the brain

High magnetic fields increase the sensitivity and spectral dispersion in magnetic resonance spectroscopy (MRS). In contrast, spectral peaks are broadened in vivo at higher field strength due to stronger susceptibility-induced effects. Strategies to minimize the spectral linewidth by optimal shimming are therefore of critical importance. The problem of shim requirements exceeding the active shim capabilities by far was overcome by a combined passive and active shim approach. In the present study, H MR spectroscopy was performed in the primary visual cortex V1 of the macaque monkey brain at 7 T.