Changho Choi1, Carol Tamminga2, Ana Stan2, Deborah Douglas1, Perry Mihalakos2, Stephanie Morris2
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA; 2Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, USA
Proton triple refocusing has been employed for measurement of glutamate (Glu) and glutamine (Gln) in human brain at 3T in vivo. A 60-ms non-space selective 180 RF pulse (bandwidth = 270 Hz), tuned to 2.4 ppm, was applied within PRESS, thereby refocusing only the resonances between 1.3 and 3.5 ppm. Subecho times were optimized, with density matrix simulation, for maximum selectivity of the Gln C4-proton multiplet, which gave (TE1, TE2, TE3) = (23, 74, 18) ms. In vivo tests were conducted on the hippocampus of five healthy volunteers. With LCModel analysis, the concentrations of Glu, Gln and NAA were estimated as 10.50.6, 2.80.7 and 9.7-0.6 mM with reference to Cr at 8 mM, with fit standard deviations of 62%, 102% and 21% respectively.