title: Correction of B 0-induced geometric distortion variations in prospective motion correction for 7T MRI.
abstract: OBJECTIVE
  Prospective motion correction can effectively fix the imaging volume of interest. For large motion, this can lead to relative motion of coil sensitivities, distortions associated with imaging gradients and B 0 field variations. This work accounts for the B 0 field change due to subject movement, and proposes a method for correcting tissue magnetic susceptibility-related distortion in prospective motion correction.
  
  
  METHODS
  The B 0 field shifts at the different head orientations were characterized. A volunteer performed large motion with prospective motion correction enabled. The acquired data were divided into multiple groups according to the object positions. The correction of B 0-related distortion was applied to each group of data individually via augmented sensitivity encoding with additionally integrated gradient nonlinearity correction.
  
  
  RESULTS
  The relative motion of the gradients, B 0 field and coil sensitivities in prospective motion correction results in residual spatial distortion, blurring, and coil artifacts. These errors can be mitigated by the proposed method. Moreover, iterative conjugate gradient optimization with regularization provided superior results with smaller RMSE in comparison to standard conjugate gradient.
  
  
  CONCLUSIONS
  The combined correction of B 0-related distortion and gradient nonlinearity leads to a reduction of residual motion artifacts in prospective motion correction data.
authors: Department of Biomedical Magnetic Resonance, Otto-von-Guericke University Magdeburg, Leipziger Str. 44 (Haus 65), 39120, Magdeburg, Germany. uten.yarach@st.ovgu.de.|Department of Radiological Technology, Chiangmai University, Chiang Mai, Thailand. uten.yarach@st.ovgu.de.
authors: Uten
authors: U
authors: Yarach
authors: Department of Physics, Kasetsart University, Bangkok, Thailand.
authors: Chaiya
authors: C
authors: Luengviriya
authors: Department of Biomedical Magnetic Resonance, Otto-von-Guericke University Magdeburg, Leipziger Str. 44 (Haus 65), 39120, Magdeburg, Germany.
authors: Daniel
authors: D
authors: Stucht
authors: Department of Biomedical Magnetic Resonance, Otto-von-Guericke University Magdeburg, Leipziger Str. 44 (Haus 65), 39120, Magdeburg, Germany.
authors: Frank
authors: F
authors: Godenschweger
authors: Department of Biomedical Magnetic Resonance, Otto-von-Guericke University Magdeburg, Leipziger Str. 44 (Haus 65), 39120, Magdeburg, Germany.|German Centre for Neurodegenerative Diseases (DZNE), Site Magdeburg, Magdeburg, Germany.
authors: Peter
authors: P
authors: Schulze
authors: Department of Biomedical Magnetic Resonance, Otto-von-Guericke University Magdeburg, Leipziger Str. 44 (Haus 65), 39120, Magdeburg, Germany.|Leibniz Institute for Neurobiology, Magdeburg, Germany.|German Centre for Neurodegenerative Diseases (DZNE), Site Magdeburg, Magdeburg, Germany.|Center for Behavioral Brain Sciences, Magdeburg, Germany.
authors: Oliver
authors: O
authors: Speck
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000000981:diagnostic imaging* / Q000503:physiopathology; D003198:Computer Simulation; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D008962:Models, Theoretical; D009038:Motion; D019047:Phantoms, Imaging
keywords: Augmented SENSE; B0 field variations; Coil sensitivity; Gradient nonlinearity; Prospective motion correction