Geometric parameters on MRA source images to differentiate small Proximal Posterior communicating artery aneurysms from Infundibular dilation.

Abstract

We aimed to assess the accuracy of magnetic resonance angiography (MRA) in the differentiation of small aneurysms versus infundibular dilations (IDs) at the internal carotid artery-posterior communicating artery (ICA-PComA) junction, emphasizing the role of MRA axial source images. This retrospective study consisted of 83 focal arterial protrusions at ICA-PComA junction in 76 patients who underwent both MRA and digital subtraction angiography (DSA)/3-dimensional rotational angiography (3DRA). The diagnostic performance of MRA for differential diagnosis of aneurysm from ID was calculated using DSA/3DRA interpretation as the standard of reference. In addition, long-axis diameter, short-axis diameter, long-axis diameter/short-axis diameter (L/S) ratio, and angle of lesion (angle of the long-axis of lesion with respect to the x-axis) measured on MRA source images were compared between aneurysms and IDs. Sensitivity, specificity, and accuracy of MRA for distinguishing aneurysms from IDs were 74.4% (57.9-87.0%) to 76.9% (60.7-88.9%), 93.2% (81.3-98.6%) to 95.5% (84.5-99.4%), and 85.5% (76.1-92.3%), respectively. Significant differences were found for the long-axis diameter (P<.001), short-axis diameter (P<.001), L/S ratio (P<.05), and angle of the lesion (P<.001) on MRA axial source images between aneurysms and IDs. The angle of the lesion had the highest discriminatory ability (area under the curve = .966 [.902-.994]) to differentiate aneurysms from IDs. An angle of lesion >60° was 89.7% (75.8-97.1%) sensitive and 100% (92.0-100.0%) specific for diagnosis of aneurysm. MRA is a useful imaging modality for distinguishing between aneurysm and ID at the ICA-PComA junction. Furthermore, geometric parameters on MRA axial source images can provide added value in their differentiation.