摘要：Two techniques commonly used on human magnetic resonance spectroscopy systems to obtain spectra from localized volumes in the brain are point resolved spectroscopy (PRESS) and stimulated echo acquisition mode (STEAM) spectroscopy. PRESS gives a signal twice as large as that obtained with STEAM, but suffers from longer minimum echo times. While STEAM must be used to detect species with short spin-spin relaxation times, PRESS can be used for species with longer relaxation times to give a spectrum with a better signal to noise ratio. Only STEAM was provided for the GE Omega 4.7 T small animal imager used in this laboratory. Therefore, a PRESS pulse program was written for this instrument. With the standard sequence, the sampled voxel is smaller than the prescribed voxel. A larger voxel can be prescribed to increase the sampled volume. A different approach, involving the modification of the gradient strength, has been used in this laboratory. The resulting pulse sequence, with representative profiles, is discussed.
