Luminal enhancement in intracranial aneurysms: fact or feature?\u2014A quantitative multimodal flow analysis

Franziska Gaidzik,Naomi Larsen,Mariya Pravdivtseva,Jan-Bernd Hövener,Olav Jansen,Philipp Berg

doi:10.1007/s11548-021-02486-y

Abstract

PurposeIntracranial aneurysm (IA) wall enhancement on post-contrast vessel wall magnetic resonance imaging (VW-MRI) is assumed to be a biomarker for vessel wall inflammation and aneurysm instability. However, the exact factors contributing to enhancement are not yet clarified. This study investigates the relationship between luminal enhancement and intra-aneurysmal flow behaviour to assess the suitability of VW-MRI as a surrogate method for determining quantitative and qualitative flow behaviour in the aneurysm sac.MethodsVW-MRI signal is measured in the lumen of three patient-specific IA flow models and compared with the intra-aneurysmal flow fields obtained using phase-contrast magnetic resonance imaging (PC-MRI) and computational fluid dynamics (CFD). The IA flow models were supplied with two different time-varying flow regimes.ResultsOverall, the velocity fields acquired using PC-MRI or CFD were in good agreement with the VW-MRI enhancement patterns. Generally, the regions with slow-flowing blood show higher VW-MRI signal intensities, whereas high flow leads to a suppression of the signal. For all aneurysm models, a signal value above three was associated with velocity values below three cm/s.ConclusionRegions with lower enhancements have been correlated with the slow and high flow at the same time. Thus, further factors like flow complexity and stability can contribute to flow suppression in addition to the flow magnitude. Nevertheless, VW-MRI can qualitatively assess intra-aneurysmal flow phenomena and estimate the velocity range present in the corresponding region.

Highlights

The prevalence of intracranial aneurysms (IA) in the adult population is estimated to be around 3% [1, 2]
IAs are generally associated with a relatively low risk of rupture, haemorrhage following the rupture of aneurysms is fatal in most cases
We aim to assess the suitability of vessel wall magnetic resonance imaging (VW-MRI) as a surrogate method for determining quantitative and qualitative flow behaviour by correlating VW-MRI

Summary

Introduction

The prevalence of intracranial aneurysms (IA) in the adult population is estimated to be around 3% [1, 2]. IAs are generally associated with a relatively low risk of rupture, haemorrhage following the rupture of aneurysms is fatal in most cases. Incidental unruptured aneurysm IAs cause significant concerns [3]. The treatment options available are associated with a variety of severe complications. A patient-specific IA rupture risk assessment is inevitable. Previous studies have identified numerous factors that are associated and correlated with a high risk of rupture such as morphological parameters (e.g., size and shape) [4, 5] and flow characteristics [6]

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