Abstract WMP33: Towards Cerebral Aneurysm Rupture Risk Prediction Using Quantitative Analysis by 4D Flow MRI: Intra-Aneurysmal Vortical Blood Flow and Association to Wall Shear Stress

Abstract

Introduction: While previous studies have shown a link between changes in aneurysmal wall shear stress (WSS) and risk of rupture, the association between the development of WSS variations and intra-aneurysmal hemodynamic flow patterns remain unknown. Understanding such link could potentially lead to novel early biomarkers for risk stratification of aneurysmal rupture. Aim: To assess the association between intra-aneurysmal flow patterns behavior and WSS in cerebral aneurysm patients. Methods: Time-resolved 3D blood flow velocities were acquired by dual-venc 4D flow MRI (kt-GRAPPA R=5, voxel size (1.0x 1.0 x 1.0 mm 3 ), TE/TR 3.5/6.2 ms, temporal resolution 57ms, venc low /venc high 50/100 cm/s) in 12 patients (66 ± 9 years, 8 F), who presented with a total of 14 cerebral aneurysms (average 10-time points per aneurysm synchronized with the cardiac cycle). Time-resolved median WSS was quantified over the 3D aneurysm surface. To quantify 3D blood flow pattern behavior from 4D Flow MRI, we used the fluid dynamics-based helicity metric. Helicity is a signed quantity that measures the strength and alignment between vortical pattern and blood flow directions. Helicity magnitudes take positive values at regions where both vortical pattern and blood flow align in the same direction while regions with opposing directions have negative values. Time-resolved positive and negative helicity were quantified separately by instantaneous volumetric median and correlated with WSS. Correlation was tested using pooled paired data of all acquired time points from all aneurysms (N=147 samples). Results: (Fig.1) Strong correlations were found between WSS and flow patterns behavior with the strongest correlation (R=0.91, p<0.001) found with negative helicity. Conclusions: We revealed that intra-aneurismal blood flow pattern behavior strongly correlates with wall shear stress. These results may help in the future to identify early hemodynamic markers for risk of aneurysmal rupture.