Resolution Enhancement of Brain Glutamate, Glutamine and Myo-Inositol by PRESS (TE1, TE2) = (37, 63) Ms at 7T

Changho Choi¹, Ivan Dimitrov^1,2, Deborah Douglas¹, Halima Hawesa¹

PRESS echo time dependences of glutamate (Glu), glutamine (Gln), N-acetylaspartate (NAA), myo-inositol (mI) and GABA were investigated for TE1 and TE2 between 30 and 200 ms, with density-matrix simulation incorporating the shaped slice-selective radio-frequency and gradient pulses, at 7T. The numerical calculation indicated that the Glu and Gln C4-proton resonance peaks can be clearly differentiated at (TE1, TE2) = (37, 63) ms, with excellent suppression of the macromolecule background signals and the neighboring abundant NAA aspartate resonances. The multiplets of mI at ~3.52 and 3.61 ppm can also be well defined with these echo times. In vivo human brain spectra from the prefrontal and left frontal lobes that were obtained with this optimized PRESS are discussed in comparison with spectra obtained with short-TE STEAM (TE = 14 ms, TM = 19 ms) and the recently-reported optimized STEAM sequence times (TE = 74 ms, TM = 68 ms). A preliminary in vivo study demonstrates the improved performance of the optimized PRESS compared to STEAM.