title: In vitro assessment of flow patterns and turbulence intensity in prosthetic heart valves using generalized phase-contrast MRI.
abstract: OBJECTIVE
  To assess in vitro the three-dimensional mean velocity field and the extent and degree of turbulence intensity (TI) in different prosthetic heart valves using a generalization of phase-contrast MRI (PC-MRI).
  
  
  METHODS
  Four 27-mm aortic valves (Björk-Shiley Monostrut tilting-disc, St. Jude Medical Standard bileaflet, Medtronic Mosaic stented and Freestyle stentless porcine valve) were tested under steady inflow conditions in a Plexiglas phantom. Three-dimensional PC-MRI data were acquired to measure the mean velocity field and the turbulent kinetic energy (TKE), a direction-independent measure of TI.
  
  
  RESULTS
  Velocity and TI estimates could be obtained up- and downstream of the valves, except where metallic structure in the valves caused signal void. Distinct differences in the location, extent, and peak values of velocity and TI were observed between the valves tested. The maximum values of TKE varied between the different valves: tilting disc, 100 J/m(3); bileaflet, 115 J/m(3); stented, 200 J/m(3); stentless, 145 J/m(3).
  
  
  CONCLUSIONS
  The TI downstream from a prosthetic heart valve is dependent on the specific valve design. Generalized PC-MRI can be used to quantify velocity and TI downstream from prosthetic heart valves, which may allow assessment of these aspects of prosthetic valvular function in postoperative patients.
authors.affiliation: Department of Cardiothoracic Surgery, Linköping University Hospital, Linköping, Sweden. john-peder.escobar.kvitting@liu.se
authors.forename: John-Peder Escobar
authors.initials: JP
authors.lastname: Kvitting
authors.forename: Petter
authors.initials: P
authors.lastname: Dyverfeldt
authors.forename: Andreas
authors.initials: A
authors.lastname: Sigfridsson
authors.forename: Stefan
authors.initials: S
authors.lastname: Franzén
authors.forename: Lars
authors.initials: L
authors.lastname: Wigström
authors.forename: Ann F
authors.initials: AF
authors.lastname: Bolger
authors.forename: Tino
authors.initials: T
authors.lastname: Ebbers
mesh_terms: D000465:Algorithms; D001021:Aortic Valve / Q000502:physiology* / Q000601:surgery; D001783:Blood Flow Velocity; D003326:Coronary Circulation / Q000502:physiology*; D019544:Equipment Failure Analysis / Q000379:methods*; D006350:Heart Valve Prosthesis; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity