title: Aneurysm growth occurs at region of low wall shear stress: patient-specific correlation of hemodynamics and growth in a longitudinal study.
abstract: OBJECTIVE
  Evolution of intracranial aneurysmal disease is known to be related to hemodynamic forces acting on the vessel wall. Low wall shear stress (WSS) has been reported to have a negative effect on endothelial cells normal physiology and may be an important contributor to local remodeling of the arterial wall and to aneurysm growth and rupture.
  
  
  METHODS
  Seven patient-specific models of intracranial aneurysms were constructed using MR angiography data acquired at two different time points (mean 16.4+/-7.4 months between the two time points). Numeric simulations of the flow in the baseline geometries were performed to compute WSS distributions. The lumenal geometries constructed from the two time points were manually coregistered, and the radial displacement of the wall was calculated on a pixel-by-pixel basis. This displacement, corresponding to the local growth of the aneurysm, was compared to the time-averaged wall shear stress (WSS TA) through the cardiac cycle at that location. For statistical analysis, radial displacement was considered to be significant if it was larger than half of the MR pixel resolution (0.3 mm).
  
  
  RESULTS
  Mean WSS TA values obtained for the areas with a displacement smaller and greater than 0.3 mm were 2.55+/-3.6 and 0.76+/-1.5 Pa, respectively (P<0.001). A linear correlation analysis demonstrated a significant relationship between WSS TA and surface displacement (P<0.001).
  
  
  CONCLUSIONS
  These results indicate that aneurysm growth is likely to occur in regions where the endothelial layer lining the vessel wall is exposed to abnormally low wall shear stress.
authors.affiliation: Department of Radiology, VA Medical Center, San Francisco, USA 94121, USA. loic.boussel@gmail.com
authors.forename: Loic
authors.initials: L
authors.lastname: Boussel
authors.forename: Vitaliy
authors.initials: V
authors.lastname: Rayz
authors.forename: Charles
authors.initials: C
authors.lastname: McCulloch
authors.forename: Alastair
authors.initials: A
authors.lastname: Martin
authors.forename: Gabriel
authors.initials: G
authors.lastname: Acevedo-Bolton
authors.forename: Michael
authors.initials: M
authors.lastname: Lawton
authors.forename: Randall
authors.initials: R
authors.lastname: Higashida
authors.forename: Wade S
authors.initials: WS
authors.lastname: Smith
authors.forename: William L
authors.initials: WL
authors.lastname: Young
authors.forename: David
authors.initials: D
authors.lastname: Saloner
mesh_terms: D000328:Adult; D000368:Aged; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D006439:Hemodynamics; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D002532:Intracranial Aneurysm / Q000473:pathology*; D008137:Longitudinal Studies; D018810:Magnetic Resonance Angiography; D008875:Middle Aged; D008955:Models, Cardiovascular; D033081:Shear Strength; D013314:Stress, Mechanical