title: Evaluation of aortic stenosis severity using 4D flow jet shear layer detection for the measurement of valve effective orifice area.
abstract: OBJECTIVE
  The objective of this study was to evaluate the potential of 4D flow MRI to assess valve effective orifice area (EOA) in patients with aortic stenosis as determined by the jet shear layer detection (JSLD) method.
  
  
  RESULTS
  An in-vitro stenosis phantom was used for validation and in-vivo imaging was performed in 10 healthy controls and 40 patients with aortic stenosis. EOA was calculated by the JSLD method using standard 2D phase contrast MRI (PC-MRI) and 4D flow MRI measurements (EOAJSLD-2D and EOAJSLD-4D, respectively). As a reference standard, the continuity equation was used to calculate EOA (EOACE) with the 2D PC-MRI velocity field and compared to the EOAJSLD measurements. The in-vitro results exhibited excellent agreement between flow theory (EOA=0.78cm(2)) and experimental measurement (EOAJSLD-4D=0.78±0.01cm(2)) for peak velocities ranging from 0.9 to 3.7m/s. In-vivo results showed good correlation and agreement between EOAJSLD-2D and EOACE (r=0.91, p<0.001; bias: -0.01±0.38cm(2); agreement limits: 0.75 to -0.77cm(2)), and between EOAJSLD-4D and EOACE (r=0.95, p<0.001; bias: -0.09±0.26cm(2); limits: 0.43 to -0.62cm(2)).
  
  
  CONCLUSIONS
  This study demonstrates the feasibility of measuring EOAJSLD using 4D flow MRI. The technique allows for optimization of the EOA measurement position by visualizing the 3D vena contracta, and avoids potential sources of EOACE measurement variability.
authors.affiliation: Radiology, Northwestern University, Chicago, USA; Medicine, Laval University, Quebec, Canada. Electronic address: julio.flores@northwestern.edu.
authors.forename: Julio
authors.initials: J
authors.lastname: Garcia
authors.affiliation: Radiology, Northwestern University, Chicago, USA; Biomedical Engineering, Northwestern University, Chicago, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Markl
authors.affiliation: Radiology, Northwestern University, Chicago, USA.
authors.forename: Susanne
authors.initials: S
authors.lastname: Schnell
authors.affiliation: Radiology, Northwestern University, Chicago, USA.
authors.forename: Bradley
authors.initials: B
authors.lastname: Allen
authors.affiliation: Radiology, Northwestern University, Chicago, USA.
authors.forename: Pegah
authors.initials: P
authors.lastname: Entezari
authors.affiliation: Radiology, Northwestern University, Chicago, USA.
authors.forename: Riti
authors.initials: R
authors.lastname: Mahadevia
authors.affiliation: Division of Cardiothoracic Surgery, Northwestern University, Chicago, USA.
authors.forename: S
authors.initials: S
authors.lastname: Chris Malaisrie
authors.affiliation: Medicine, Laval University, Quebec, Canada.
authors.forename: Philippe
authors.initials: P
authors.lastname: Pibarot
authors.affiliation: Radiology, Northwestern University, Chicago, USA.
authors.forename: James
authors.initials: J
authors.lastname: Carr
authors.affiliation: Radiology, Northwestern University, Chicago, USA.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Barker
mesh_terms: D000328:Adult; D001021:Aortic Valve / Q000473:pathology*; D001024:Aortic Valve Stenosis / Q000473:pathology*; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods; D003287:Contrast Media; D005240:Feasibility Studies; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA
keywords: 4D flow MRI; Aortic stenosis; Effective orifice area; Jet shear layer