Statistical wall shear stress maps of ruptured and unruptured middle cerebral artery aneurysms

Abstract

Haemodynamics and morphology play an important role in the genesis, growth and rupture of cerebral aneurysms. The goal of this study was to generate and analyse statistical wall shear stress (WSS) distributions and shapes in middle cerebral artery (MCA) saccular aneurysms. Unsteady flow was simulated in seven ruptured and 15 unruptured MCA aneurysms. In order to compare these results, all geometries must be brought in a uniform coordinate system. For this, aneurysms with corresponding WSS data were transformed into a uniform spherical shape; then, all geometries were uniformly aligned in threedimensional space. Subsequently, we compared statistical WSS maps and surfaces of ruptured and unruptured aneurysms. No significant ( p . 0.05) differences exist between ruptured and unruptured aneurysms regarding radius and mean WSS. In unruptured aneurysms, statistical WSS map relates regions with high (greater than 3 Pa) WSS to the neck region. In ruptured aneurysms, additional areas with high WSS contiguous to regions of low (less than 1 Pa) WSS are found in the dome region. In ruptured aneurysms, we found significantly lower WSS. The averaged aneurysm surface of unruptured aneurysms is round shaped, whereas the averaged surface of ruptured cases is multi-lobular. Our results confirm the hypothesis of low WSS and irregular shape as the essential rupture risk parameters.

Analysis of Morphologic and Hemodynamic Parameters for Unruptured Posterior Communicating Artery Aneurysms with Oculomotor Nerve Palsy

“…Some studies revealed lower WSS on ruptured aneurysms than on asymptomatic unruptured ones. 5,7,16 A CFD study of hemodynamic differences between unruptured and ruptured IAs during observation has been reported recently. Thirteen aneurysms that ruptured during the course of follow-up observation were included in this study, and averaged WSS in the unruptured group was lower than in the rup- tured group in the MCA.…”

Modeling and simulation of flow in cerebral aneurysms

“…The mean value averaged over 10 pulses at Re = 250 is found to be around 1.4 Pa with peak values near 2.6 Pa. At higher (possibly pathological) Reynolds number Re = 400 we observe a change in mean value up to 2.5 Pa and a considerable increase in peak values to 6.2 Pa averaged over 10 pulses. These values show the same general magnitude as reported in [29,70]. Transitional dynamics is clearly observed in Figure 4.5(b).…”

“…We consider a full range of physiologically relevant conditions and show that the flow undergoes a transition from an orderly state at low Reynolds numbers (Re = 100, 200), in which the pulsatile forcing is closely followed in time, to a complex response with strongly increased high-frequency components at higher Reynolds numbers (Re = 400), i.e., at higher flow rates and larger aneurysm sizes. The results obtained for the shear stress correspond to values found in literature [29,70], thereby providing an additional validation of the computational model. The numerical reliability of the predicted transition is quantified on the basis of the bounding solutions approach.…”

CFD: Computational Fluid Dynamics or Confounding Factor Dissemination? The Role of Hemodynamics in Intracranial Aneurysm Rupture Risk Assessment

“…Simulations have steadily migrated from idealized geometries to patient-specific IA geometries, from steady-state flow to pulsatile flow, and from qualitative flow pattern descriptions 20,22,23,43 to sophisticated quantitative statistical analyses. 4,5,30 Furthermore, efforts to bolster statistical power have increased the number of patient-specific IA cases per hemodynamic study from 1 (in the year 2003) 44 to 210 (in the year 2011). 5 Worldwide interactions between engineers and clinicians, exemplified by the annual International Intracranial Stent Meeting (http://www.ics-meeting.net), have stressed the dire medical need for clinically relevant information, including rupture risk assessments.…”

“…5,30,31 Alternatively, some authors prefer to examine the spatial maximum (MWSS in Online Table 1) of TAWSS in an aneurysm. Both values require identification of the IA neck and an objective method to isolate the aneurysm.…”