Intracranial aneurysm stiffness assessment using 4D flow MRI

Background Although arterial stiffness is a known biomarker for cardiovascular events and stroke, there is limited information in the literature regarding the stiffness of intracranial aneurysms. This study aimed to assess intracranial aneurysm stiffness using four-dimensional flow magnetic resonance imaging (4D flow MRI). Methods A total of 27 aneurysms in 25 patients with internal carotid artery aneurysms were included. Using 4D flow MRI, we measured the arterial pulse waveform during a cardiac cycle at planes proximal and distal to the target aneurysm. The damping of these waveforms through the aneurysm was defined as the aneurysm damping index (ADI) and compared with that of the contralateral side. Additionally, we investigated the clinical factors associated with the ADI. Results ADI assessment was successful in all cases. The obtained ADI was 1.18 ± 0.28 (mean ± standard deviation), significantly larger than 1.0 (P=0.0027 [t-test]). The ADI on the aneurysm side was larger than on the contralateral side (1.19 ± 0.30 vs 1.05 ± 0.17, P=0.029 [t-test]). On multivariate analysis, the use of beta-blockers (β=0.46, P=0.015) and smoking history (β=-0.22, P=0.024) showed a significant correlation with ADI. Conclusions We proposed a novel method to assess the stiffness of intracranial aneurysms using 4D flow MRI. The quantitative observation of the damping of arterial pulse waves revealed a correlation between ADI and clinical factors, such as the use of antihypertensive drugs and smoking. Further studies should focus on evaluating the aneurysm stiffness and its clinical applications.