title: Generalized versus patient-specific inflow boundary conditions in computational fluid dynamics simulations of cerebral aneurysmal hemodynamics.
abstract: OBJECTIVE
  Attempts have been made to associate intracranial aneurysmal hemodynamics with aneurysm growth and rupture status. Hemodynamics in aneurysms is traditionally determined with computational fluid dynamics by using generalized inflow boundary conditions in a parent artery. Recently, patient-specific inflow boundary conditions are being implemented more frequently. Our purpose was to compare intracranial aneurysm hemodynamics based on generalized versus patient-specific inflow boundary conditions.
  
  
  METHODS
  For 36 patients, geometric models of aneurysms were determined by using 3D rotational angiography. 2D phase-contrast MR imaging velocity measurements of the parent artery were performed. Computational fluid dynamics simulations were performed twice: once by using patient-specific phase-contrast MR imaging velocity profiles and once by using generalized Womersley profiles as inflow boundary conditions. Resulting mean and maximum wall shear stress and oscillatory shear index values were analyzed, and hemodynamic characteristics were qualitatively compared.
  
  
  RESULTS
  Quantitative analysis showed statistically significant differences for mean and maximum wall shear stress values between both inflow boundary conditions (P < .001). Qualitative assessment of hemodynamic characteristics showed differences in 21 cases: high wall shear stress location (n = 8), deflection location (n = 3), lobulation wall shear stress (n = 12), and/or vortex and inflow jet stability (n = 9). The latter showed more instability for the generalized inflow boundary conditions in 7 of 9 patients.
  
  
  CONCLUSIONS
  Using generalized and patient-specific inflow boundary conditions for computational fluid dynamics results in different wall shear stress magnitudes and hemodynamic characteristics. Generalized inflow boundary conditions result in more vortices and inflow jet instabilities. This study emphasizes the necessity of patient-specific inflow boundary conditions for calculation of hemodynamics in cerebral aneurysms by using computational fluid dynamics techniques.
authors.affiliation: From the Departments of Radiology (I.G.H.J., J.J.S., W.V.P., R.B., H.A.M., C.B.L.M.M.) i.g.jansen@amc.uva.nl.
authors.forename: I G H
authors.initials: IG
authors.lastname: Jansen
authors.affiliation: From the Departments of Radiology (I.G.H.J., J.J.S., W.V.P., R.B., H.A.M., C.B.L.M.M.).
authors.forename: J J
authors.initials: JJ
authors.lastname: Schneiders
authors.affiliation: From the Departments of Radiology (I.G.H.J., J.J.S., W.V.P., R.B., H.A.M., C.B.L.M.M.).
authors.forename: W V
authors.initials: WV
authors.lastname: Potters
authors.affiliation: Department of Radiology (P.O.), Northwestern University, Chicago, Illinois.
authors.forename: P
authors.initials: P
authors.lastname: van Ooij
authors.affiliation: From the Departments of Radiology (I.G.H.J., J.J.S., W.V.P., R.B., H.A.M., C.B.L.M.M.).
authors.forename: R
authors.initials: R
authors.lastname: van den Berg
authors.affiliation: Biomedical Engineering and Physics (E.T.B., H.A.M.), Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: van Bavel
authors.affiliation: From the Departments of Radiology (I.G.H.J., J.J.S., W.V.P., R.B., H.A.M., C.B.L.M.M.)Biomedical Engineering and Physics (E.T.B., H.A.M.), Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: H A
authors.initials: HA
authors.lastname: Marquering
authors.affiliation: From the Departments of Radiology (I.G.H.J., J.J.S., W.V.P., R.B., H.A.M., C.B.L.M.M.).
authors.forename: C B L M
authors.initials: CB
authors.lastname: Majoie
mesh_terms: D000368:Aged; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D057446:Hydrodynamics; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D011859:Radiography; D013314:Stress, Mechanical