title: Reproducibility of flow and wall shear stress analysis using flow-sensitive four-dimensional MRI.
abstract: OBJECTIVE
  To systematically investigate the scan-rescan reproducibility and observer variability of flow-sensitive four-dimensional (4D) MRI in the aorta for the assessment of blood flow and global and segmental wall shear stress.
  
  
  METHODS
  ECG and respiration-synchronized flow-sensitive 4D MRI data (spatio-temporal resolution = 1.7 × 2.0 × 2.2 mm(3) /40.8 ms) were acquired in 12 healthy volunteers. To analyze scan-rescan variability, flow-sensitive 4D MRI was repeated in 10 volunteers during a second visit. Data analysis included calculation of time-resolved and total flow, peak systolic velocity, and regional and global wall shear stress (WSS) in up to 24 analysis planes distributed along the aorta.
  
  
  RESULTS
  Scan-rescan, inter-observer, and intra-observer agreement was excellent for the calculation of total flow and peak systolic velocity (mean differences <5% of the average flow parameter). Global WSS demonstrated moderate agreement and increased variability regarding wall shear stress (scan-rescan, inter-observer, and intra-observer agreement; mean differences <10% of the average WSS parameters). The segmental distribution of wall shear stress in the thoracic aorta could reliably be reproduced (r > 0.87; P < 0.001) for different observers and examinations.
  
  
  CONCLUSIONS
  Flow-sensitive 4D MRI-based analysis of aortic blood flow can be performed with good reproducibility. Robustness of global and regional WSS quantification was limited, but spatio-temporal WSS distributions could reliably be replicated.
authors: Department of Radiology - Medical Physics, University Hospital Freiburg, Germany. michael.markl@uniklinik-freiburg.de
authors: Michael
authors: M
authors: Markl
authors: Wolf
authors: W
authors: Wallis
authors: Andreas
authors: A
authors: Harloff
mesh_terms: D001011:Aorta / Q000473:pathology; D001783:Blood Flow Velocity; D003198:Computer Simulation; D003952:Diagnostic Imaging / Q000379:methods; D004562:Electrocardiography / Q000379:methods; D006439:Hemodynamics; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008858:Microscopy, Phase-Contrast / Q000379:methods; D015588:Observer Variation; D015203:Reproducibility of Results; D033081:Shear Strength; D013314:Stress, Mechanical