Aneurysmal wall enhancement and hemodynamics: pixel-level correlation between spatial distribution

Background: Inflammation and hemodynamics are interrelated risk factors for intracranial aneurysm rupture. This study aimed to identify the relationship between these risk factors from an individual-patient perspective using biomarkers of aneurysm wall enhancement (AWE) derived from high-resolution magnetic resonance imaging (HR-AIRI) and hemodynamic parameters by four-dimensional flow MRI (4D-flow MRI). Methods: A total of 29 patients with 29 unruptured intracranial aneurysms larger than 4 mm were included in this prospective cross-sectional study. A total of 24 aneurysms had AWE and 5 did not have AWE. A three-dimensional (3D) vessel model of each individual aneurysm was generated with 3D time-of-flight magnetic resonance angiography (3D TOF-MRA). Quantification of AWE was sampled with HR-MRI. Time-averaged wall shear stress (WSS) and oscillatory shear index (OSI) were calculated from the 4D-flow MRI. The correlation between spatial distribution of AWE and hemodynamic parameters measured at pixel-level was evaluated for each aneurysm. Results: In aneurysms with AWE, the spatial distribution of WSS was negatively correlated with AWE in 100% (24/24) of aneurysms, though 2 had an absolute value of the correlation coefficient <0.1. The OSI was positively correlated with AWE in 90.9% (22/24) of aneurysms; the other 2 aneurysms showed a negative correlation with AWE. in aneurysms with no AWE, there was no correlation between WSS (100%, 5/5), OSI (80%, 4/5), and wall inflammation. Conclusions: The spatial distribution of WSS was negatively correlated with AWE in aneurysms with AWE, and OSI was positively correlated with AWE in most aneurysms with AWE. While aneurysms that did not contain AWE showed no correlation between hemodynamics and wall inflammation.

Automated summary

This study explored the relationship between inflammation, hemodynamics, and intracranial aneurysm rupture risk factors using high-resolution magnetic resonance imaging and four-dimensional flow MRI. The results showed a negative correlation between the spatial distribution of wall shear stress (WSS) and aneurysm wall enhancement (AWE) in aneurysms with AWE, and a positive correlation between oscillatory shear index (OSI) and AWE in most aneurysms with AWE. Aneurysms without AWE showed no correlation between hemodynamics and wall inflammation.