Homonuclear uncoupled 1H-spectroscopy of the human brain using weighted accumulation schemes

Homonuclear uncoupled H-spectroscopy based on 2-dimensional (2D) J-resolved spectroscopy is a well suited technique for the assessment of J-coupled metabolite resonances. In comparison with 1-dimensional H-spectroscopy this technique largely reduces problems due to spectral overlap between low molecular weight metabolite resonances and superimposed broad macromolecule resonances, as well as overlap between adjacent multiplets. Usually, 2D J-resolved spectroscopic data were acquired using a constant number of accumulations for each of the various echo times. In contrast to this, a weighted accumulation scheme has been applied in this study, using an echo time dependent number of accumulations. The aims of this modification were to reduce the acquisition time and to improve the signal-to-noise ratio per unit acquisition time (SNRt). Four different sine-bell like accumulation schemes and a reference scheme using a constant number of accumulations have been applied on five normal volunteers. Localized spectra obtained from the parieto-occipital white matter were compared with regard to SNRt and linewidth. A reduction in acquisition time of 45%, related to the reference scheme, and an increase in SNRt of 25-30% were achieved using a sine-bell accumulation scheme in combination with a quarter sine-wave apodization of the short echo time data. Down to an acquisition time of 122 s no significant line broadening has been observed in comparison with the reference scheme.