Quantification of aneurysm wall enhancement in intracranial fusiform aneurysms and related predictors based on high-resolution magnetic resonance imaging: a validation study

Abstract

Background: Aneurysm wall enhancement (AWE) in high-resolution magnetic resonance imaging (HR-MRI) has emerged as a new imaging biomarker of intracranial aneurysm instability.

Objective: To determine a standard method of AWE quantification for predicting fusiform intracranial aneurysms (FIAs) stability by comparing the sensitivity of each parameter in identifying symptomatic FIAs. The predictors of AWE and FIA types were also identified.

Methods: We retrospectively analyzed consecutive fusiform aneurysm patients who underwent HR-MRI from two centers. The aneurysm-to-pituitary stalk contrast ratio (CR_stalk), aneurysm enhancement ratio, and aneurysm enhancement index were extracted, and their sensitivities in discriminating aneurysm symptoms were compared using the receiver-operating characteristic curve. Morphological parameters of fusiform aneurysm were extracted based on 3D vessel model. Uni- and multivariate analyses of related predictors for AWE, CR_stalk, and FIA types were performed, respectively.

Results: Overall, 117 patients (mean age, 53.3 ± 11.7 years; male, 75.2%) with 117 FIAs underwent HR-MRI were included. CR_stalk with the maximum signal intensity (CR_stalk-max) had the highest sensitivity in identifying symptomatic FIAs with an area under the curve value (0.697) and a cut-off value of 0.90. The independent predictors of AWE were aneurysm symptoms [(odds ratio) OR = 3.754, p = 0.003], aspirin use (OR = 0.248, p = 0.037), and the maximum diameter of the cross-section (OR = 1.171, p = 0.043). The independent predictors of CR_stalk-max were aneurysm symptoms (OR = 1.289, p = 0.003) and posterior circulation aneurysm (OR = 1.314, p = 0.001). Transitional-type showed higher rates of hypertension and mural thrombus over both dolichoectatic- and fusiform-type FIAs.

Conclusion: CR_stalk-max may be the most reliable parameter to quantify AWE to distinguish symptomatic FIAs. It also has the potential to identify unstable FIAs. Several factors contribute to the complex pathophysiology of FIAs and need further validation in a larger cohort.

Keywords: fusiform aneurysm; magnetic resonance imaging; symptoms; validation; vessel wall imaging.

Figure 1.

Quantification of D_max and L_max in the 3D space. (a) The 3D vessel model was first extracted from 3D TOF MRA. (b) The centerline of the vessel was then automatically extracted. (c and d) Finally, L_max was calculated based on the boundary definition, and D_max was measured in the cross-section.

Figure 2.

Post-contrast 3D T1-weighted images revealed the 20 mm² of corpus callosum (red circle), four points of the pituitary infundibulum (black plus), and fusiform aneurysm of the right vertebral artery (white triangle).

Figure 3.

Flowchart of patient selection.

Figure 4.

Assessment of aneurysm morphology and AWE in fusiform, dolichoectatic, and transitional FIAs. The upper column shows 3D TOF MRA, the middle column shows AWE of three types of FIA, and the bottom column shows D_max (yellow line) and L_max (red line).

Figure 5.

ROC curves for CR_stalk-max, AER_max, AEI_max, CR_{stalk-average}, and AEI_average with AUC values of 0.697, 0.675, 0.624, 0.622, and 0.613, respectively.