title: Impact of aneurysmal geometry on intraaneurysmal flow: a computerized flow simulation study.
abstract: BACKGROUND
  This study was performed to assess the effect of aneurysm geometry on parameters that may have an impact on the natural history of intracranial aneurysms, such as intraaneurysmal flow pressure and shear stress.
  
  
  METHODS
  Flow was simulated in 21 randomly selected aneurysms using finite volume modeling. Ten aneurysms were classified as side-wall aneurysms, with either single-sided or circumferential involvement of the parent artery wall, and 11 as bifurcation aneurysms (symmetric or asymmetric), with an axis either perpendicular or parallel to the parent artery. The flow patterns were classified as either jet or vortex types (with regular or irregular vortex flow). Pressures and shear stresses were characterized as evenly or unevenly distributed over the aneurysm wall and neck.
  
  
  RESULTS
  All side-wall and four of the bifurcation aneurysms with a perpendicular axis had a vortex type flow pattern and seven bifurcation aneurysms with a parallel axis (four symmetric and two asymmetric) had a jet flow pattern. Jet type flow was associated with an uneven pressure distribution in seven out of seven aneurysms. Vortex type flow resulted in an even pressure distribution in five out of six aneurysms with an irregular flow pattern and six out of eight with a regular flow pattern. No firm relationship could be established between any geometrical type and shear stress distribution. Only 1 of 14 aneurysms with a perpendicular axis, but 4 of 7 aneurysms with a parallel axis, had ruptured.
  
  
  CONCLUSIONS
  Aneurysm geometry does have an impact on flow conditions. Aneurysms with a main axis parallel to the parent artery have a tendency to have a jet flow pattern and uneven distribution of unsteady pressure. These aneurysms may have a higher rate of rupture as than those with a main axis perpendicular to the parent artery.
authors.affiliation: Interventional Neuroradiology, National Institute of Neurosurgery, Budapest, Hungary. h13424szi@ella.hu
authors.forename: Istvan
authors.initials: I
authors.lastname: Szikora
authors.forename: Gyorgy
authors.initials: G
authors.lastname: Paal
authors.forename: Adam
authors.initials: A
authors.lastname: Ugron
authors.forename: Ferenc
authors.initials: F
authors.lastname: Nasztanovics
authors.forename: Miklos
authors.initials: M
authors.lastname: Marosfoi
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Berentei
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Kulcsar
authors.forename: Wickly
authors.initials: W
authors.lastname: Lee
authors.forename: Imre
authors.initials: I
authors.lastname: Bojtar
authors.forename: Istvan
authors.initials: I
authors.lastname: Nyary
mesh_terms: D017542:Aneurysm, Ruptured / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D001783:Blood Flow Velocity / Q000502:physiology; D002533:Cerebral Angiography; D020342:Finite Element Analysis; D018056:Hemorheology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008959:Models, Neurological; D012039:Regional Blood Flow / Q000502:physiology*; D012189:Retrospective Studies; D014655:Vascular Resistance / Q000502:physiology