title: Four-dimensional flow magnetic resonance imaging-based characterization of aortic morphometry and haemodynamics: impact of age, aortic diameter, and valve morphology.
abstract: OBJECTIVE
  Four-dimensional (4D) flow magnetic resonance imaging (MRI) was employed for the simultaneous assessment of morphometry and flow parameters along the thoracic aorta to investigate associations between flow, age, aorta diameter, and aortic valve morphology.
  
  
  RESULTS
  One hundred and sixty-five subjects, 65 controls, 50 patients with bicuspid aortic valve (BAV), and 50 patients with a dilated aorta, and a tricuspid aortic valve (TAV) underwent 4D flow MRI. Following 3D segmentation of the aorta, a vessel centreline was calculated and used to extract aorta diameter, peak systolic velocity, and normalized systolic flow displacement. Validation of 4D flow MRI-based morphometric measurements compared with manual diameter measurements from standard contrast-enhanced MR angiography in 20 controls showed good agreement (mean difference = 0.4 mm, limits of agreement = ±1.31 mm) except at the sinus of valsalva. BAV showed significant differences in average peak velocity (PV; P < 0.016) compared with TAV and controls between the left ventricle outflow tract to sino-tubular junction (BAV: 1.3 ± 0.3 m/s; TAV: 1.2 ± 0.2 m/s; controls: 1.0 ± 0.1 m/s) and the ascending aorta for average normalized flow displacement (BAV: 0.11 ± 0.02; TAV: 0.09 ± 0.02; controls: 0.06 ± 0.01, P < 0.016) despite similar average aortic dimensions for BAV (37 ± 1 mm) and TAV (39 ± 1 mm). Multivariate linear regression showed a significant correlation of maximal aortic diameter to age, PV, and normalized flow displacement (R(2) = 0.413, P < 0.001).
  
  
  CONCLUSIONS
  A single acquisition of 4D flow MRI characterized local morphological and haemodynamic differences between groups along the aorta. BAV showed altered haemodynamics when compared with TAV in spite of having similar aorta dimensions. Maximal aorta diameter was associated with age, PV, and normalized flow displacement.
authors.affiliation: Department of Radiology, Northwestern University, 737 N Michigan, Suite 1600, Chicago, IL 60611, USA.
authors.forename: Julio
authors.initials: J
authors.lastname: Garcia
authors.affiliation: Department of Radiology, Northwestern University, 737 N Michigan, Suite 1600, Chicago, IL 60611, USA.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Barker
authors.affiliation: Department of Radiology, Northwestern University, 737 N Michigan, Suite 1600, Chicago, IL 60611, USA.
authors.forename: Ian
authors.initials: I
authors.lastname: Murphy
authors.affiliation: Department of Radiology, Northwestern University, 737 N Michigan, Suite 1600, Chicago, IL 60611, USA Biomedical Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Kelly
authors.initials: K
authors.lastname: Jarvis
authors.affiliation: Department of Radiology, Northwestern University, 737 N Michigan, Suite 1600, Chicago, IL 60611, USA.
authors.forename: Susanne
authors.initials: S
authors.lastname: Schnell
authors.affiliation: Department of Radiology, Northwestern University, 737 N Michigan, Suite 1600, Chicago, IL 60611, USA.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Collins
authors.affiliation: Department of Radiology, Northwestern University, 737 N Michigan, Suite 1600, Chicago, IL 60611, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Carr
authors.affiliation: Division of Cardiothoracic Surgery, Northwestern University, Chicago, IL, USA.
authors.forename: S Chris
authors.initials: SC
authors.lastname: Malaisrie
authors.affiliation: Department of Radiology, Northwestern University, 737 N Michigan, Suite 1600, Chicago, IL 60611, USA Biomedical Engineering, Northwestern University, Evanston, IL, USA mmarkl@northwestern.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Markl
mesh_terms: D000328:Adult; D000367:Age Factors; D001018:Aortic Diseases / Q000000981:diagnostic imaging / Q000473:pathology*; D001021:Aortic Valve / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000473:pathology; D000082882:Bicuspid Aortic Valve Disease; D016022:Case-Control Studies; D016208:Databases, Factual; D019561:Echocardiography, Four-Dimensional / Q000379:methods*; D005260:Female; D006349:Heart Valve Diseases / Q000000981:diagnostic imaging / Q000473:pathology*; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012016:Reference Values; D012189:Retrospective Studies; D018570:Risk Assessment; D012737:Sex Factors; D014261:Tricuspid Valve / Q000000981:diagnostic imaging / Q000473:pathology*
keywords: Aortic diseases; Haemodynamics; Magnetic resonance imaging