FLIP ANGLE EFFECTS IN STEAM AND PRESS - OPTIMIZED VERSUS SINC RF PULSES

Flip angle dependence of the localized single-voxel H-1 NMR spectrosco pic sequences STEAM and PRESS using numerically optimized Shinnar-Le R oux (SLR) and conventional sine RF pulses has been evaluated, Phantom experiments were used to evaluate voxel profiles from MR images of the selected voxels. Information on the total excited volume was recorded from the integrated area under the water peak in the localized spectr um at different flip angles (theta = 0 degrees-180 degrees). The voxel profiles for both the STEAM and PRESS sequences using the SLR RF puls es were found to be identical, unlike the case for the sine RF pulses. The SLR RF pulses in the PRESS sequence were found to be more sensiti ve to flip angle variations, Localized, water-suppressed H-1 NMR spect ra recorded from the frontal gray matter in healthy volunteers (n = 3) showed less lipid contamination using the SLR RF pulses compared with the sine RF pulses. (C) 1998 Academic Press.