title: Quantification of aortic stenosis diagnostic parameters: comparison of fast 3 direction and 1 direction phase contrast CMR and transthoracic echocardiography.
abstract: BACKGROUND
  Aortic stenosis (AS) is a common valvular disorder, and disease severity is currently assessed by transthoracic echocardiography (TTE). However, TTE results can be inconsistent in some patients, thus other diagnostic modalities such as cardiovascular magnetic resonance (CMR) are demanded. While traditional unidirectional phase-contrast CMR (1Dir PC-CMR) underestimates velocity if the imaging plane is misaligned to the flow direction, multi-directional acquisitions are expected to improve velocity measurement accuracy. Nonetheless, clinical use of multidirectional techniques has been hindered by long acquisition times. Our goal was to quantify flow parameters in patients using 1Dir PC-CMR and a faster multi-directional technique (3Dir PC-CMR), and compare to TTE.
  
  
  METHODS
  Twenty-three patients were prospectively assessed with TTE and CMR. Slices above the aortic valve were acquired for both PC-CMR techniques and cine SSFP images were acquired to quantify left ventricular stroke volume. 3Dir PC-CMR implementation included a variable density sampling pattern with acceleration rate of 8 and a reconstruction method called ReVEAL, to significantly accelerate acquisition. 3Dir PC-CMR reconstruction was performed offline and ReVEAL-based image recovery was performed on the three (x, y, z) encoding pairs. 1Dir PC-CMR was acquired with GRAPPA acceleration rate of 2 and reconstructed online. CMR derived flow parameters and aortic valve area estimates were compared to TTE.
  
  
  RESULTS
  ReVEAL based 3Dir PC-CMR derived parameters correlated better with TTE than 1Dir PC-CMR. Correlations ranged from 0.61 to 0.81 between TTE and 1Dir PC-CMR and from 0.61 to 0.87 between TTE and 3Dir-PC-CMR. The correlation coefficients between TTE, 1Dir and 3Dir PC-CMR Vpeakwere 0.81 and 0.87, respectively. In comparison to ReVEAL, TTE slightly underestimates peak velocities, which is not surprising as TTE is only sensitive to flow that is parallel to the acoustic beam.
  
  
  CONCLUSIONS
  By exploiting structure unique to PC-CMR, ReVEAL enables multi-directional flow imaging in clinically feasible acquisition times. Results support the hypothesis that ReVEAL-based 3Dir PC-CMR provides better estimation of hemodynamic parameters in AS patients in comparison to 1Dir PC-CMR. While TTE can accurately measure velocity parallel to the acoustic beam, it is not sensitive to the other directions of flow. Therefore, multi-directional flow imaging, which encodes all three components of the velocity vector, can potentially outperform TTE in patients with eccentric or multiple jets.
authors.affiliation: Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA.|InCor Heart Institute, University of São Paulo Medical School, São Paulo, SP, Brazil.
authors.forename: Juliana Serafim
authors.initials: JS
authors.lastname: da Silveira
authors.affiliation: Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Smyke
authors.affiliation: Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, USA.
authors.forename: Adam V
authors.initials: AV
authors.lastname: Rich
authors.affiliation: Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA.
authors.forename: Yingmin
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Siemens Healthcare, Erlangen, Germany.
authors.forename: Ning
authors.initials: N
authors.lastname: Jin
authors.affiliation: Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA.
authors.forename: Debbie
authors.initials: D
authors.lastname: Scandling
authors.affiliation: Department of Internal Medicine, Division of Cardiovascular Medicine, The Ohio State University, Columbus, OH, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Dickerson
authors.affiliation: InCor Heart Institute, University of São Paulo Medical School, São Paulo, SP, Brazil.
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Rochitte
authors.affiliation: Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA.|Department of Internal Medicine, Division of Cardiovascular Medicine, The Ohio State University, Columbus, OH, USA.
authors.forename: Subha V
authors.initials: SV
authors.lastname: Raman
authors.affiliation: Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, USA.
authors.forename: Lee C
authors.initials: LC
authors.lastname: Potter
authors.affiliation: Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA.|Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, USA.
authors.forename: Rizwan
authors.initials: R
authors.lastname: Ahmad
authors.affiliation: Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA. Orlando.Simonetti@osumc.edu.|Department of Internal Medicine, Division of Cardiovascular Medicine, The Ohio State University, Columbus, OH, USA. Orlando.Simonetti@osumc.edu.|Department of Radiology, The Ohio State University, 460 W. 12th Avenue, room 320, 43210, Columbus, OH, USA. Orlando.Simonetti@osumc.edu.
authors.forename: Orlando P
authors.initials: OP
authors.lastname: Simonetti
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001021:Aortic Valve / Q000000981:diagnostic imaging* / Q000503:physiopathology; D001024:Aortic Valve Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D001783:Blood Flow Velocity; D015150:Echocardiography, Doppler; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012720:Severity of Illness Index
keywords: Aortic stenosis; Bayesian model; Multi-directional phase contrast CMR; Phase contrast imaging; Transthoracic echocardiography