Fast Parallel Spiral Chemical Shift Imaging at 3T Using Iterative Sense Reconstruction

Abstract

Spiral chemical shift imaging (CSI) is a fast CSI technique that speeds up the data acquisition in comparison to conventional phase-encoded CSI by sampling the data while oscillating gradients are applied in two spatial dimensions. This enables the simultaneous encoding of 1D spectral and 2D spatial information. Therefore, it potentially allows one to perform a 2D-CSI experiment in a single shot. However, for most applications, limitations on maximum gradient strength and slew rate make multiple excitations necessary in order to achieve a desired spectral bandwidth. For these additional excitations either the start of the data acquisition is shifted (spectral interleaves) or the spiral k-space trajectory is rotated (spatial interleaves) with each interleaf. Parallel imaging techniques such as simultaneous acquisition of spatial harmonics (SMASH), sensitivity encoding (SENSE), or generalized autocalibrating partially parallel acquisitions (GRAPPA), have been developed to accelerate the acquisition in MRI by utilizing complementary spatial encoding afforded by the spatially inhomogeneous sensitivity profiles of individual receiver coils. The performance of the new method was evaluated in phantom and in vivo experiments. Parallel spiral CSI produced maps of brain metabolites similar to those obtained using conventional gridding reconstruction of the fully sampled data with only a small decrease in time-normalized signal-to-noise ratio and a small increase in noise for higher acceleration factors. Magn Reson Med 59:891–897, 2008. © 2008 Wiley-Liss, Inc.