Changho Choi1, Subroto Ghose2, Ivan Dimitrov1,3, Deborah Douglas1, Perry Mihalakos2
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA; 2Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, USA; 3Philips Medical Systems, Cleveland, OH, USA
N-acetylaspartylglutamate (NAAG) in human brain has been measured with difference editing at 7T. The C3 proton resonances (~2.5 ppm) of the aspartyl groups of NAAG and N-acetylaspartate (NAA) were differentiated using a 20 ms Gaussian radio-frequency (RF) pulse (bandwidth = 57 Hz) for selective excitation of the their coupling partners at 4.61 and 4.38 ppm, respectively. Symmetric carriers of the editing 180 pulse were applied to separate NAAG and NAA completely. In vivo measurement was conducted on the medial prefrontal and the left frontal lobes of a healthy volunteer. Assuming identical relaxation times between NAAG and NAA, the concentration of NAAG was estimated to be 1 and 2.3 mM for prefrontal and left frontal, respectively, with reference to NAA at 9 mM.