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Minimizing lipid signal bleed in brain 1 H chemical shift imaging by post‐acquisition grid shifting
Author(s) -
Zhang Yi,
Zhou Jinyuan,
Bottomley Paul A.
Publication year - 2015
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.25438
Subject(s) - voxel , image resolution , artifact (error) , nuclear magnetic resonance , signal (programming language) , resolution (logic) , artificial intelligence , chemistry , computer science , physics , programming language
Purpose Low spatial resolution in conventional 1 H 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 pa rtial volume correctio n employing g rid s hifting (“PANGS”) is presented, which minimizes residual PVE without compromising spatial resolution. Methods PANGS shifts the locations of the reconstruction coordinates in a designated region of image space—the 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 1 H CSI human studies employing outer volume suppression and long echo times. Results PANGS 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. Conclusion PANGS significantly reduces lipid artifacts in 1 H brain CSI spectra and metabolite maps, and improves metabolite detection in cortical regions without compromising resolution. Magn Reson Med 74:320–329, 2015. © 2014 Wiley Periodicals, Inc.