High field localized proton spectroscopy in small volumes: greatly improved localization and shimming using shielded strong gradients.

The availability of shielded gradients facilitates accurate single-voxel spectroscopy. Exact localization (90-99%) of volumes as small as 2 x 2 x 2 mm is demonstrated using a modified stimulated echo sequence. Strong gradient pulses (up to 200 mT/m) are employed to clear the stimulated echo of unwanted magnetization, enabling superior (single-scan) shimming of the selected volume. In vivo and in vitro proton NMR results at 4.7 T are presented.