Fast magnetic resonance spectroscopic imaging (MRSI) using wavelet encoding and parallel imaging: in vitro results

In previous work we have shown that wavelet encoding spectroscopic imaging (WE-SI) reduces acquisition time and voxel contamination compared to the standard Chemical Shift Imaging (CSI) also known as phase encoding (PE). In this paper, we combine the wavelet encoding method with parallel imaging (WE-PI) technique to further reduce the acquisition time by the acceleration factor R, and preserve the spatial metabolite distribution. Wavelet encoding provides results with a lower signal-to-noise ratio (SNR) than the phase encoding method. Their combination with parallel imaging, introduces an intrinsic SNR reduction. The rate of SNR reduction is slower in wavelet encoding with PI than PE with parallel imaging (PE-PI). This is due to the fact that in WE-PI, the SNR reduction is a function of the acceleration factor R and the voxel number N, whereas in PE-PI it is a function of the acceleration factor R only.