HOMONUCLEAR J-REFOCUSED SPECTRAL EDITING TECHNIQUE FOR QUANTIFICATIONOF GLUTAMINE AND GLUTAMATE BY H-1-NMR SPECTROSCOPY

Quantification of the excitatory amino acid of glutamine and glutamate is extremely important partly because, when in excessive amounts, the y can produce neuronal damage. However, quantification of such metabol ites seems to be not straightforward owing to a large number of metabo lic signals, particularly between the 2.0- and 3.0-ppm chemical shift range. The authors investigated a quantification method by using a hom onuclear J-refocused spectral editing technique, namely the J-refocuse d PRESS (JPRESS), using both 1.5- and 4-T whole body NMR systems. At f irst, the J-coupling modulation of each metabolite at different TE val ues using the PRESS and JPRESS pulse sequences was compared. The suppr ession of J modulations with the JPRESS is well demonstrated on condit ion that TE values are less than 1/4J. Then, the accuracy of glutamate quantification after subtracting the two spectra obtained at two diff erent echo times and integrating the difference spectral area at diffe rent concentrations was evaluated. The results exhibit an excellent li near relationship between the actual concentration versus the differen ce spectral peak area at both 1.5 and 4 T. The achievable minimum voxe l size was also considered and a 1-ml voxel size seems to be possible at the typical glutamate concentration in vivo at a field strength of 4 T.