A comparison of spatially resolved spectroscopy and stimulated echo acquisition mode sequences for volume-localized spectroscopy

Studies have been performed to compare the spatially resolved spectroscopy (SPARS) sequence and the stimulated echo acquisition mode (STEAM) sequence. Slice profile and imaging studies were performed using phantoms to compare the quality of localization with the two sequences when the volume of interest (VOI) was moved away from the magnet isocenter. Experiments were also performed to compare the spectral quality obtained with the two sequences, especially when the VOI was moved away from the magnet isocenter. These studies indicate that the definition of the VOI, signal-to-noise ratio, and spectral resolution obtained with STEAM were comparable at different spatial locations within the sample. This, however, was not true when using SPARS due to the phase shifts induced by the spatially dependent gradient settling times. Furthermore, these studies indicate that the spectral quality obtained with SPARS was compromised due to off resonance effects when the pulse lengths of the hard pulses were long.