title: Increasing the spatial resolution and sensitivity of magnetic resonance elastography by correcting for subject motion and susceptibility-induced image distortions.
abstract: To improve the resolution of elasticity maps by adapting motion and distortion correction methods for phase-based magnetic resonance imaging (MRI) contrasts such as magnetic resonance elastography (MRE), a technique for measuring mechanical tissue properties in vivo.
  
  
  
  MRE data of the brain were acquired with echo-planar imaging (EPI) at 3T (n = 14) and 7T (n = 18). Motion and distortion correction parameters were estimated using the magnitude images. The real and imaginary part of the complex MRE data were corrected separately and recombined. The width of the point-spread function (PSF) and the position variability were calculated. The images were normalized to the Montreal Neurological Institute (MNI) anatomical template. The gray-to-white matter separability of the elasticity maps was tested.
  
  
  
  Motion correction sharpened the |G*| maps as demonstrated by a narrowing of the PSF by 0.78 ± 0.51 mm at 7T and 0.52 ± 0.63 mm at 3T. The amount of individual head motion during MRE acquisition correlated with the decrease in the width of the PSF at 7T (r = 0.53, P = 0.025) and at 3T (r = 0.69, P = 0.006) and with the increase of gray-to-white matter separability after motion correction at 7T (r = 0.64, P = 0.0039) and at 3T (r = 0.57, P = 0.0319). Improved spatial accuracy after distortion correction results in a significant increase in separability of gray and white matter stiffness (P = 0.0067), especially in inferior parts of the brain suffering from strong B0inhomogeneities.
  
  
  
  We demonstrate that our method leads to sharper images and higher spatial accuracy, raising the prospect of the investigation of smaller brain areas with increased sensitivity in studies using MRE.
  
  
  
  1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:134-141.
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Andreas
authors.identifier: 0000-0003-0448-7138
authors.initials: A
authors.lastname: Fehlner
authors.affiliation: Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hirsch
authors.affiliation: Berlin Center for Advanced Neuroimaging, Charité - Universitätsmedizin Berlin, Berlin, Germany.|Bernstein Center for Computational Neuroscience, Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Weygandt
authors.affiliation: Berlin Center for Advanced Neuroimaging, Charité - Universitätsmedizin Berlin, Berlin, Germany.|Bernstein Center for Computational Neuroscience, Berlin, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Christophel
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Eric
authors.initials: E
authors.lastname: Barnhill
authors.affiliation: Berlin Center for Advanced Neuroimaging, Charité - Universitätsmedizin Berlin, Berlin, Germany.|Bernstein Center for Computational Neuroscience, Berlin, Germany.
authors.forename: Mykola
authors.initials: M
authors.lastname: Kadobianskyi
authors.affiliation: Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Braun
authors.affiliation: Institute of Biometry and Medical Informatics, Otto-von-Guericke University, Magdeburg, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Bernarding
authors.affiliation: Institute of Biometry and Medical Informatics, Otto-von-Guericke University, Magdeburg, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Lützkendorf
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Ingolf
authors.initials: I
authors.lastname: Sack
authors.affiliation: Berlin Center for Advanced Neuroimaging, Charité - Universitätsmedizin Berlin, Berlin, Germany.|Bernstein Center for Computational Neuroscience, Berlin, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Hetzer
mesh_terms: D000328:Adult; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D017352:Echo-Planar Imaging / Q000379:methods*; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009038:Motion; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: MR elastography; distortion correction; motion correction; multifrequency MRE; phase-based contrast