title: Spatial resolution and velocity field improvement of 4D-flow MRI.
abstract: 4D-flow MRI obtains a time-dependent 3D velocity field; however, its use for the calculation of higher-order parameters is limited by noise. We present an algorithm for denoising 4D-flow data.
  
  
  
  By integrating a velocity field and eliminating streamlines in noisy flow, depicted by high curvature, a denoised dataset may be extracted. This method, defined as the velocity field improvement (VFIT) algorithm, was validated in an analytical dataset and using in vivo data in comparison with a computation fluid dynamics (CFD) simulation. As a proof of principal, wall shear stress (WSS) measurements in the descending aorta were compared with those defined by CFD.
  
  
  
  The VFIT algorithm achieved a >100% noise reduction of a corrupted analytical dataset. In addition, 4D-flow data were cleaned to show improved spatial resolution and near wall velocity representation. WSS measures compared well with CFD data and bulk flow dynamics were retained (<2% difference in flow measurements).
  
  
  
  This study presents a method for denoising 4D-flow datasets with improved spatial resolution. Bulk flow dynamics are accurately conserved while velocity and velocity gradient fields are improved; this is important in the calculation of higher-order parameters such as WSS, which are shown to be more comparable to CFD measures. Magn Reson Med 78:1959-1968, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Sydney Translational Imaging Laboratory, Heart Research Institute, Charles Perkins Centre, University of Sydney, Sydney, Australia.|Sydney Medical School, University of Sydney, Camperdown, Australia.
authors.forename: Fraser M
authors.initials: FM
authors.lastname: Callaghan
authors.affiliation: Sydney Translational Imaging Laboratory, Heart Research Institute, Charles Perkins Centre, University of Sydney, Sydney, Australia.|Sydney Medical School, University of Sydney, Camperdown, Australia.|Department of Radiology, Royal Prince Alfred Hospital, Camperdown, Australia.
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Grieve
mesh_terms: D000328:Adult; D000465:Algorithms; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging; D001783:Blood Flow Velocity; D003198:Computer Simulation; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male
keywords: 4D-flow; denoising; wall shear stress