title: 4D flow magnetic resonance imaging in bicuspid aortic valve disease demonstrates altered distribution of aortic blood flow helicity.
abstract: OBJECTIVE
  Changes in aortic geometry or presence of aortic valve (AoV) disease can result in substantially altered aortic hemodynamics. Dilatation of the ascending aorta or AoV abnormalities can result in an increase in helical flow.
  
  
  METHODS
  4D flow magnetic resonance imaging was used to test the feasibility of quantitative helicity analysis using equidistantly distributed 2D planes along the entire aorta. The evaluation of the method included three parts: (1) the quantification of helicity in 12 healthy subjects, (2) an evaluation of observer variability and test-retest reliability, and (3) the quantification of helical flow in 16 patients with congenitally altered bicuspid AoVs.
  
  
  RESULTS
  Helicity quantification in healthy subjects revealed consistent directions of flow rotation along the entire aorta with high clockwise helicity in the aortic arch and an opposite rotation sense in the ascending and descending aorta. The results demonstrated good scan-rescan and inter- and intraobserver agreement of the helicity parameters. Helicity quantification in patients revealed a significant increase in absolute peak relative helicity during systole and a considerably greater heterogeneous distribution of mean helicity in the aorta.
  
  
  CONCLUSIONS
  The method has the potential to serve as a reference distribution for comparisons of helical flow between healthy subjects and patients or between different patient groups.
authors.affiliation: Department of Radiology, Medical Physics, University Medical Center Freiburg, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Lorenz
authors.forename: J
authors.initials: J
authors.lastname: Bock
authors.forename: A J
authors.initials: AJ
authors.lastname: Barker
authors.forename: F
authors.initials: F
authors.lastname: von Knobelsdorff-Brenkenhoff
authors.forename: W
authors.initials: W
authors.lastname: Wallis
authors.forename: J G
authors.initials: JG
authors.lastname: Korvink
authors.forename: M M
authors.initials: MM
authors.lastname: Bissell
authors.forename: J
authors.initials: J
authors.lastname: Schulz-Menger
authors.forename: M
authors.initials: M
authors.lastname: Markl
mesh_terms: D000328:Adult; D001011:Aorta / Q000473:pathology* / Q000503:physiopathology*; D001021:Aortic Valve / Q000002:abnormalities* / Q000473:pathology / Q000503:physiopathology; D000082882:Bicuspid Aortic Valve Disease; D001783:Blood Flow Velocity; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods; D005240:Feasibility Studies; D005260:Female; D006349:Heart Valve Diseases / Q000473:pathology* / Q000503:physiopathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: aorta; aortic valve disease; bicuspid aortic valve; blood flow helicity; helicity quantification