Selective homonuclear Hartmann-Hahn transfer method for in vivo spectral editing in the human brain

Abstract

A novel selective homonuclear Hartmann-Hahn transfer method for in vivo spectral editing is proposed and applied to measurements of γ-aminobutyric acid (GABA) in the human brain at 3 T. The proposed method utilizes a new concept for in vivo spectral editing, the spectral selectivity of which is not based on a conventional editing pulse but based on the stringent requirement of the doubly selective Hartmann-Hahn match. The sensitivity and spectral selectivity of GABA detection achieved by this doubly selective Hartmann-Hahn match scheme was superior to that achievable by conventional in vivo spectral editing techniques providing both sensitivity enhancement and excellent suppression of overlapping resonances in a single shot. Since double-quantum filtering gradients were not employed, singlets such as the NAA methyl group at 2.02 ppm and the creatine methylene group at 3.92 ppm were detected simultaneously. These singlets may serve as navigators for the spectral phase of GABA and for frequency shifts during measurements. The estimated concentration of GABA in the frontoparietal region of the human brain in vivo was 0.7 ± 0.2 μmol/g (mean ± SD, n = 12).