Neil Wilson1, Kevin D'Aquilla1, Catherine Debrosse1, Hari Hariharan1, and Ravinder Reddy1
Ultrafast z-spectroscopy can be collected by saturating the nuclear spins with an RF pulse in the presence of a gradient, effectively encoding the offset frequency spatially across a voxel and allowing full z-spectra to be collected in a single shot. When asymmetry analysis is applied, frequencies on one physical side of the voxel are compared with those on the other physical side. This can be a problem if there is inhomogeneity or partial voluming. By acquiring an additional z-spectrum with the gradient polarity reversed, mixed z-spectra can be created in which the positive and negative offset frequencies come from the same side of the voxel. This method is more robust to inhomogeneity and partial voluming typically found in vivo as demonstrated here with studies on 7T in human brain.