title: Relative residence time prolongation in intracranial aneurysms: a possible association with atherosclerosis.
abstract: BACKGROUND
  Intracranial aneurysms can have atherosclerotic wall properties that may be important in predicting aneurysm history or estimating the potential risks of surgical treatments.
  
  
  OBJECTIVE
  To investigate hemodynamic characteristics of atherosclerotic lesions in intracranial aneurysms using computational fluid dynamics.
  
  
  METHODS
  Intraoperative video recordings of 30 consecutive patients with an unruptured middle cerebral artery aneurysm were examined to identify atherosclerotic lesions on an aneurysm wall. For computational fluid dynamics analyses, geometries of aneurysms and adjacent arteries were reconstructed from 3-dimensional rotational angiography. Transient simulations were conducted under patient-specific pulsatile inlet conditions measured by phase-contrast magnetic resonance velocimetry. Three hemodynamic wall parameters were calculated: time-averaged wall shear stress, oscillatory shear index, and relative residence time (RRT). Statistical analyses were performed to discriminate the risk factors of atherosclerotic lesion formation.
  
  
  RESULTS
  Among 30 aneurysms, 7 atherosclerotic lesions with remarkable yellow lipid deposition were identified in 5 aneurysms. All 7 atherosclerotic lesions spatially agreed with the area with prolonged RRT. Univariate analysis revealed that male sex (P = .03), cigarette smoking (P = .047), and maximum RRT (P = .02) are significantly related to atherosclerotic lesion on the intracranial aneurysmal wall. Of those variables that influenced atherosclerotic lesion of the intracranial aneurysmal wall, male sex (P = .005) and maximum RRT (P = .004) remained significant in the multivariate regression model.
  
  
  CONCLUSIONS
  The area with prolonged RRT colocalized with atherosclerotic change on the aneurysm wall. Male sex and maximum RRT were independent risk factors for atherogenesis in intracranial aneurysms.
authors.affiliation: *Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Japan; ‡Department of Neuroanesthesia, and ¶Department of Neurosurgery, Kohnan Hospital, Sendai, Japan; §Graduate School of Biomedical Engineering, and #Institute of Fluid Science, Tohoku University, Sendai, Japan; ‖Department of Neurosurgery, Sendai Medical Center, Sendai, Japan.
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Sugiyama
authors.forename: Kuniyasu
authors.initials: K
authors.lastname: Niizuma
authors.forename: Toshio
authors.initials: T
authors.lastname: Nakayama
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Shimizu
authors.forename: Hidenori
authors.initials: H
authors.lastname: Endo
authors.forename: Takashi
authors.initials: T
authors.lastname: Inoue
authors.forename: Miki
authors.initials: M
authors.lastname: Fujimura
authors.forename: Makoto
authors.initials: M
authors.lastname: Ohta
authors.forename: Akira
authors.initials: A
authors.lastname: Takahashi
authors.forename: Teiji
authors.initials: T
authors.lastname: Tominaga
mesh_terms: D000328:Adult; D000368:Aged; D050197:Atherosclerosis / Q000150:complications* / Q000175:diagnosis*; D002533:Cerebral Angiography; D003198:Computer Simulation; D003936:Diagnosis, Computer-Assisted; D005260:Female; D006801:Humans; D057446:Hydrodynamics; D021621:Imaging, Three-Dimensional; D002532:Intracranial Aneurysm / Q000150:complications* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D059035:Perioperative Period