Magnetization transfer attenuation of creatine resonances in localized proton MRS of human brain in vivo

To assess putative magnetization transfer effects on the proton resonances of cerebral metabolites in human brain, we performed quantitative proton ma gnetic resonance spectroscopy (2.0 T, STEAM, TR/TE/TM = 6000/40/10 ms. LCMo del data evaluation) of white matter (7.68 mL, 10 healthy young subjects) i n the absence and presence of fast repetitive off-resonance irradiation (2. 1 kHz from the water resonance) using a train of 100 Gaussian-shaped RF pul ses (12.8 ms duration, 120 Hz nominal bandwidth, 40 ms repetition period, 1 080 degrees nominal flip angle). A comparison of pertinent metabolite conce ntrations revealed a magnetization transfer attenuation factor of the methy l and methylene resonances of creatine and phosphocreatine of 0.87 +/- 0.05 (p < 0.01). No attenuation was observed for the resonances of N-acetylaspa rtate and N-acetylaspartylglutamate, glutamate and glutamine, choline-conta ining compounds, and myo-inositol. The finding fur total creatine is in exc ellent agreement with data reported for rat brain. The results are consiste nt with the hypothesis of a chemical exchange of mobile creatine or phospho creatine molecules with a small immobilized or 'bound' pool. Copyright (C) 1999 John Wiley & Sons, Ltd.