Inflow Angle Impacts Morphology, Hemodynamics, and Inflammation of Side-wall Intracranial Aneurysms.

ABSTRACT

BACKGROUND: Aneurysm inflow angle has been shown to be associated with hemodynamic changes by computational fluid dynamics. However, these studies were based on single aneurysm model and were limited to side-wall aneurysms. PURPOSE: To investigate the association between inflow angle and morphology, hemodynamic, and inflammation of intracranial side-wall and bifurcation aneurysms. STUDY TYPE Prospective. POPULATION A total of 62 patients (aged 58.34 ± 12.39, 44 female) with 59 unruptured side-wall aneurysms and 17 unruptured bifurcation aneurysms were included. FIELD STRENGTH/SEQUENCE A 3.0 T; 3D fast field echo sequence (TOF-MRA); free-breathing, 3D radio-frequency-spoiled, multi-shot turbo field echo sequence (4D-flow MRI); 3D black-blood T1-weighted volumetric turbo spin echo acquisition sequence (T1 -VISTA) ASSESSMENT Two neuroradiologists assessed the inflow angle and size for intracranial aneurysms in 3D space with TOF-MRA images. The average and maximum inflow velocity (Vavg-IA , Vmax-IA ), blood flow (Flowavg-IA , Flowmax-IA ), and average wall shear stress (WSSavg-IA ) for aneurysms were assessed from 4D-flow MRI in regions of interest drawn by two neuroradiologists. The aneurysmal wall enhancement (AWE) grades between precontrast and postcontrast T1 -VISTA images were evaluated by three neuroradiologists. STATISTICAL TESTS Kruskal-Wallis H test, χ2 test, Pearson's correlation coefficient, scatter plots and regression lines, multivariate logistic regression analysis (partial correlation r) were performed. A P < 0.05 was considered statistically significant. RESULTS: The WSSavg-IA (0.52 ± 0.34 vs. 0.27 ± 0.22) and AWE grades (1.38 ± 1.04 vs. 2.02 ± 0.68) between the two inflow angle subgroups of side-wall aneurysms were significantly different. The aneurysm size (rs  = 0.31), WSSavg-IA (rs  = -0.45), and AWE grades (rs  = 0.45) were significantly correlated with inflow angle in side-wall aneurysms. While in bifurcation aneurysms, there were no significant associations between inflow angle and size (P = 0.901), Vavg-IA (P = 0.699), Vmax-IA (P = 0.482), Flowavg-IA (P = 0.550), Flowmax-IA (P = 0.689), WSSavg-IA (P = 0.573), and AWE grades (P = 0.872). DATA CONCLUSION: A larger aneurysm size, a lower WSS and a higher AWE grade were correlated with a larger inflow angle in side-wall aneurysms. EVIDENCE LEVEL 3 TECHNICAL EFFICACY Stage 2.