Accelerated Proton Echo Planar Spectroscopic Imaging (PEPSI) Using GRAPPA with a 32-Channel Phased-Array

Parallel imaging has been demonstrated to reduce the encod-ing time of MR spectroscopic imaging (MRSI). Here we inves-tigate up to 5-fold acceleration of 2D proton echo planar spec-troscopic imaging (PEPSI) at 3T using generalized autocalibrat-ing partial parallel acquisition (GRAPPA) with a 32-channel coil array, 1.5 cm3 voxel size, TR/TE of 15/2000 ms, and 2.1 Hz spectral resolution. Compared to an 8-channel array, the smaller RF coil elements in this 32-channel array provided a 3.1-fold and 2.8-fold increase in signal-to-noise ratio (SNR) in the peripheral region and the central region, respectively, and more spatial modulated information. Comparison of sensitivity-encoding (SENSE) and GRAPPA reconstruction using an 8-channel array showed that both methods yielded similar quantitative metabolite measures (P> 0.1). Concentration val-ues of N-acetyl-aspartate (NAA), total creatine (tCr), cholin