title: Three-dimensional hemodynamics in intracranial aneurysms: influence of size and morphology.
abstract: OBJECTIVE
  To use four-dimensional (4D)-flow MRI for the comprehensive in vivo analysis of hemodynamics and its relationship to size and morphology of different intracranial aneurysms (IA). We hypothesize that different IA groups, defined by size and morphology, exhibit different velocity fields, wall shear stress, and vorticity.
  
  
  METHODS
  The 4D-flow MRI (spatial resolution = 0.99-1.8 × 0.78-1.46 × 1.2-1.4 mm(3) , temporal resolution = 44-48 ms) was performed in 19 IAs (18 patients, age = 55.4 ± 13.8 years) with saccular (n = 16) and fusiform (n = 3) morphology and different sizes ranging from small (n = 8; largest dimension = 6.2 ± 0.4 mm) to large and giant (n = 11; 25 ± 7 mm). Analysis included quantification of volumetric spatial-temporal velocity distribution, vorticity, and wall shear stress (WSS) along the aneurysm's 3D surface.
  
  
  RESULTS
  The 4D-flow MRI revealed distinct hemodynamic patterns for large/giant saccular aneurysms (Group 1), small saccular aneurysms (Group 2), and large/giant fusiform aneurysms (Group 3). Saccular IA (Groups 1, 2) demonstrated significantly higher peak velocities (P < 0.002) and WSS (P < 0.001) compared with fusiform aneurysms. Although intra-aneurysmal 3D velocity distributions were similar for Group 1 and 2, vorticity and WSS was significantly (P < 0.001) different (increased in Group 1 by 54%) indicating a relationship between IA size and hemodynamics. Group 3 showed reduced velocities (P < 0.001) and WSS (P < 0.001).
  
  
  CONCLUSIONS
  The 4D-flow MRI demonstrated the influence of lesion size and morphology on aneurysm hemodynamics suggesting the potential of 4D-flow MRI to assist in the classification of individual aneurysms.
authors.affiliation: Department of Radiology, Northwestern University, Chicago, Illinois, USA.
authors.forename: Susanne
authors.initials: S
authors.lastname: Schnell
authors.forename: Sameer A
authors.initials: SA
authors.lastname: Ansari
authors.forename: Parmede
authors.initials: P
authors.lastname: Vakil
authors.forename: Marie
authors.initials: M
authors.lastname: Wasielewski
authors.forename: Maria L
authors.initials: ML
authors.lastname: Carr
authors.forename: Michael C
authors.initials: MC
authors.lastname: Hurley
authors.forename: Bernard R
authors.initials: BR
authors.lastname: Bendok
authors.forename: Hunt
authors.initials: H
authors.lastname: Batjer
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Carroll
authors.forename: James
authors.initials: J
authors.lastname: Carr
authors.forename: Michael
authors.initials: M
authors.lastname: Markl
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000783:Aneurysm; D001783:Blood Flow Velocity; D015331:Cohort Studies; D005260:Female; D006439:Hemodynamics; D006801:Humans; D021621:Imaging, Three-Dimensional; D002532:Intracranial Aneurysm / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D015203:Reproducibility of Results; D033081:Shear Strength; D013314:Stress, Mechanical
keywords: 4D-flow MRI; WSS; hemodynamics; intracranial aneurysms; velocity; vorticity