LOCALIZED PROTON SPECTROSCOPY USING STIMULATED ECHOES

This paper describes a new method for spatially resolved NMR spectroscopy that takes advantage of stimulated echo signals. STEAM (stimulated echo acquisition mode) sequences, already used for a variety of imaging purposes, almost perfectly match the requirements of image-controlled localized 1H NMR in vivo. Superior spatial discrimination as well as high flexibility with respect to location, size, and shape of the volume of interest is achieved by employing only three slice-selective 90° rf pulses in the presence of orthogonal gradients. The method is a single-step procedure minimizing rf power requirements and gradient switches. It further allows accurate determinations of localized T1 and T2 relaxation times simply by varying the length of corresponding intervals of the STEAM sequence. In fact, the inherent T2 weighting may be used for water suppression and/or reduction of residual eddy current effects. Here we present first results on phantoms and human extremities demonstrating the ease of image selection, localized spectroscopy, and localized determinations of relaxation times. Future steps will deal with water/lipid-suppressed metabolic spectroscopy. © 1987.