Abstract 1122‐000213: Presence of Blebs Associated with Reduced Aneurysm Wall Tension and Increased Wall Enhancement

Abstract

Introduction : Aneurysm wall enhancement using high‐resolution vessel wall imaging (HR‐VWI) may provide new surrogate biomarkers for instability. Finite element analysis (FEA) paired with HR‐VWI can provide more insight into complex morphological features that ultimately lead to aneurysm growth and rupture. Methods : Unruptured intracranial aneurysms were reconstructed in 3D from CE‐MRA imaging. Shells were created assuming a uniform wall thickness of 86 μm and FEA was conducted with a 3rd order polynomial material model, assuming the wall to be isotropic, homogenous, and similar between subjects. The 95th percentile wall tension was defined as high wall tension to account for mesh artifacts. Low wall tension was identified from nodal values and verified on contour plots. Regions of high and low wall tension were characterized from contour plots. Aneurysms were measured and classified as enhancing (CR stalk ≥0.6) or non‐enhancing (CR stalk <0.6), using manual ROI measurements from 3T HR‐VWI T1 postcontrast imaging. Results : Of the twenty‐three aneurysms analyzed, fourteen were classified as enhancing (CR stalk ≥0.6) and nine as non‐enhancing. Enhancing aneurysms had a significantly higher 95th percentile wall tension (m = 0.89±0.32 N/cm) compared to non‐enhancing aneurysms (m = 0.48±0.10 N/cm, p<0.001). Wall enhancement remained a significant predictor of wall tension while accounting for the effects of aneurysm size (p = 0.046). High wall tension was consistently concentrated at the neck of the aneurysm, while low wall tension concentrated at the dome. (Figure 1). Aneurysms with blebs (N = 7) had significantly lower minimal wall tension (m = 0.13±0.02 N/cm) than those without (m = 0.21±0.10 N/cm, p = 0.033). Enhancing aneurysms had significantly higher minimal wall tensions (m = 0.23±0.10 N/cm), than non‐enhancing aneurysms (m = 0.13±0.02 N/cm, 0.003). Minimal wall tension was less strongly correlated with diameter and neck size (Spearman’s r = 0.564,0.378 respectively) than 95th percentile wall tension (Spearman’s r = 0.756, 0.541 respectively). Conclusions : Large and irregular aneurysms are subject to complex mechanical loading. The resultant stress concentrators may prompt the histological remodeling response observed in areas of growth, like the aneurysm neck. Low wall tension indicative of wall degradation in areas more prone to rupture colocalized with aneurysm wall enhancement and blebs.