1H NMR spectroscopic imaging of the monkey brain using binomial water suppression in a stimulated-echo sequence

A new proton, two-dimensional pulse sequence for 1H NMR spectroscopic imaging (chemical shift imaging) was tested in phantoms and in the monkey brain. The pulse sequence consisted of one binomial chemically selective pulse and two spatially selective pulses in the stimulated-echo sequence. The point-spread function (which is influenced by k-space filtering and the number of phase-encoded steps) of a 1 mm source phantom was measured using a 16 x 16 spatial matrix and was found to have a FWHM of 10 mm (100 mm field of view) with very little rippling outside the main lobe. The binomial excitation profile was measured in order to correct the NMR intensity for the variable flip angles. Spectroscopic images were measured in the monkey brain with a 15 mm slice thickness and a 16 x 16 spatial matrix. Proton spectra derived from the brain contained sharp resonances of choline, creatine and N-acetyl aspartate with minimal lipid contamination. Proton spectra derived from the subcutaneous fat and adipose tissue behind the eyes contained large lipid resonances.