Minimizing lipid signal bleed in brain 1H chemical shift imaging by post-acquisition grid shifting

PurposeLow spatial resolution in conventional H-1 brain chemical shifting imaging (CSI) studies causes partial volume error (PVE) or signal bleed that is especially deleterious to voxels near the scalp. The standard spatial apodization approach adversely affects spatial resolution. Here, a novel automated post-processing strategy of (PANGS) is presented, which minimizes residual PVE without compromising spatial resolution. MethodsPANGS shifts the locations of the reconstruction coordinates in a designated region of image spacethe scalp, to match the tissue centers-of-mass instead of the geometric centers of each voxel, by iteratively minimizing the PVE from the scalp into outside voxels. PANGS' performance was evaluated by numerical simulation, and in 3 Tesla H-1 CSI human studies employing outer volume suppression and long echo times. ResultsPANGS reduced lipid contamination of cortical spectra by up to 86% (54% on average). Metabolite maps exhibited significantly less lipid artifact than conventional and spatially-filtered CSI. All methods generated quantitatively identical spectral peak areas from central brain locations, but spatial filtering increased spectral linewidths and reduced spatial resolution. ConclusionPANGS significantly reduces lipid artifacts in H-1 brain CSI spectra and metabolite maps, and improves metabolite detection in cortical regions without compromising resolution. Magn Reson Med 74:320-329, 2015. (c) 2014 Wiley Periodicals, Inc.