3-DIMENSIONAL SPECTROSCOPIC IMAGING WITH TIME-VARYING GRADIENTS

A spectroscopic imaging sequence with a time-varying readout gradient in the slice selection direction is used to image multiple contiguous slices. For a given voxel size, the imaging time and signal-to-noise r atio of the three-dimensional spectroscopic sequence are the same as f or a single slice acquisition without the oscillating readout gradient . The data reconstruction employs a gridding algorithm in two dimensio ns to interpolate the nonuniformly sampled data onto a Cartesian grid, and a fast Fourier transform in four dimensions: three spatial dimens ions and the spectral dimension. The method is demonstrated by in vivo imaging of NAA in human brain at 1.5 T with 10 slices of 16 x 16 pixe ls spectroscopic images acquired in a total scan time of 17 min.