Measurement of the T 2 relaxation time of ethanol and cerebral metabolites, in vivo

The SPACE volume selection technique was combined with a spin‐echo sequence to measure the transverse relaxation time of the resonances of ethanol and cerebral metabolites in the dog brain, in vivo . The method was extended to measure brain metabolite T 2 , values in the rat using 1 H NMR microspectroscopy. The T 2 decays for the resonances of the metabolites N‐acetylaspartate, creatine/phosphocreatine, and choline/phosphorylcholine were found to be biexponential with long T 2 components of 490, 260, and 350 ms for the dog and 490, 220, and 355 ms for the rat brain, respectively. The existence of a second T 2 component may originate from J ‐coupled nonresolved metabolite resonances. The relaxation decay for the ethanol triplet could be fitted to a single exponential giving a T 2 relaxation time of 335 ms. However, given the large errors in the measurement of ethanol peak intensities at short echo times because of overlapping lipid signal and the effects of J ‐modulation, a biexponential decay with a long T 2 component of 335 ms cannot be ruled out. Ambiguities regarding the reported partial detection of the 1 H NMR signal of ethanol in the brain are discussed. © 1992 Academic Press, Inc.