Changho Choi1, Ivan Dimitrov1,2, Deborah Douglas1, Halima Hawesa1
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA; 2Philips Medical Systems, Cleveland, OH, USA
Glycine (Gly) in human brain has been measured using an optimized PRESS (point-resolved spectroscopy) sequence at 7T. Echo time dependences of the coupled resonances of myo-inositol, choline and threonine were investigated for TE1 and TE2 between 20 and 200 ms with 1 ms increments, using the density matrix simulation incorporating the volume selective radio-frequency and gradient pulses. The numerical simulation indicated that the Gly selectivity is maximized at (TE1, TE2) = (100, 48) ms. LC model fitting was used for in vivo data analysis. The fit standard deviation of Gly was ≤ 8% in all three spectra (scan time ~5 min). The Gly concentration in human brain was estimated to be 0.6, 0.8 and 0.8 mM for the medial prefrontal, fronto-parietal and occipital cortices with reference to creatine at 8 mM, respectively.