Hemodynamic-morphologic discriminants for intracranial aneurysm rupture

Abstract

Background and purpose: the purpose of this study was to identify significant morphological and hemodynamic parameters that discriminate intracranial aneurysm rupture status using 3-dimensional angiography and computational fluid dynamics.

Methods: one hundred nineteen intracranial aneurysms (38 ruptured, 81 unruptured) were analyzed from 3-dimensional angiographic images and computational fluid dynamics. Six morphological and 7 hemodynamic parameters were evaluated for significance with respect to rupture. Receiver operating characteristic analysis identified area under the curve (AUC) and optimal thresholds separating ruptured from unruptured aneurysms for each parameter. Significant parameters were examined by multivariate logistic regression analysis in 3 predictive models-morphology only, hemodynamics only, and combined-to identify independent discriminants, and the AUC receiver operating characteristic of the predicted probability of rupture status was compared among these models.

Results: morphological parameters (size ratio, undulation index, ellipticity index, and nonsphericity index) and hemodynamic parameters (average wall shear stress [WSS], maximum intra-aneurysmal WSS, low WSS area, average oscillatory shear index, number of vortices, and relative resident time) achieved statistical significance (P<0.01). Multivariate logistic regression analysis demonstrated size ratio to be the only independently significant factor in the morphology model (AUC, 0.83; 95% CI, 0.75 to 0.91), whereas WSS and oscillatory shear index were the only independently significant variables in the hemodynamics model (AUC, 0.85; 95% CI, 0.78 to 0.93). The combined model retained all 3 variables, size ratio, WSS, and oscillatory shear index (AUC, 0.89; 95% CI, 0.82 to 0.96).

Conclusions: all 3 models-morphological (based on size ratio), hemodynamic (based on WSS and oscillatory shear index), and combined-discriminate intracranial aneurysm rupture status with high AUC values. Hemodynamics is as important as morphology in discriminating aneurysm rupture status.

Figure 1

Flow patterns for 8 representative ruptured (top) and 10 unruptured (bottom) intracranial aneurysms (IAs). On each of the middle cross-sectional plane flow pattern visualizations, the cross-sectional velocity vector plane has been overlapped on top of the corresponding aneurysm geometry to clearly show the cutting plane. ACA=anterior cerebral artery, ACOM=anterior communicating artery, BA=basilar artery, ICA=internal carotid artery, MCA=middle cerebral artery, PCA=posterior cerebral artery, PCOM=posterior communicating artery.

Figure 2

Wall shear stress (WSS) distributions for 8 representative ruptured (top) and 10 unruptured (bottom) IAs.

Figure 3

Oscillatory shear index (OSI) distribution for 8 representative ruptured (top) and 10 unruptured (bottom) IAs.

Figure 4

Scatter plots (A) showing the distribution of key parameters in unruptured and ruptured cases. Red square represents ruptured aneurysm data and blue triangle represents unruptured aneurysm data and receiver-operating characteristic (ROC) curve (B) for key parameters size ratio (SR), WSS, and OSI.