title: Minimizing lipid signal bleed in brain (1) H chemical shift imaging by post-acquisition grid shifting.
abstract: OBJECTIVE
  Low spatial resolution in conventional 1H 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 partial volume correction employing grid shifting ("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 1H 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.
  
  
  CONCLUSIONS
  PANGS significantly reduces lipid artifacts in 1H brain CSI spectra and metabolite maps, and improves metabolite detection in cortical regions without compromising resolution.
authors.affiliation: Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.|Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.|F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.
authors.forename: Jinyuan
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.|Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland, USA.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Bottomley
mesh_terms: D000328:Adult; D000465:Algorithms; D016477:Artifacts; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D002794:Choline / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D005260:Female; D006801:Humans; D050356:Lipid Metabolism / Q000502:physiology*; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult
chemical_list: D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline
keywords: CSI; MRS; brain; lipid bleed; metabolite quantification; partial volume error; postprocessing