Diagnostic Performance of MRA for UnrupturedAneurysms at the Distal ICA.

Purpose: Unruptured intracranial aneurysms (UIAs) at the distal internal carotid artery (ICA) (segments C5-C7) are difficult to accurately display on computed tomography angiography (CTA) due to the influences of bone structures and vessel curvature. We investigated the utility of three-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA) at 3.0‑T for the detection of morphologic features compared to digital subtraction angiography (DSA).

Methods: This retrospective study included 2398 patients between January 2015 and May 2020 who underwent 3D-TOF-MRA and DSA within 3 months. Morphologic features including aneurysm size, neck width, shape and relation to adjacent arteries and other diagnostic parameters were recorded. Three observers blinded to the clinical and DSA results independently analyzed MRA data sets. The statistical difference of each aneurysm-specific variable was performed using χ²-tests and multivariate logistic regression analysis.

Results: A total of 551 aneurysms in 514 patients were confirmed at the distal ICA by DSA. Patient-based, aneurysm-based and location-based evaluations with 3D-TOF-MRA yielded high diagnostic accuracy in the detection of target UIAs. The accuracy of displayed morphologic features was 94.9% for size, 97.2% for neck width, 92.6% for shape, and 96.4% for relationship to adjacent vessels. Multivariate logistic regression showed that tiny (P < 0.001) or giant (P = 0.039) size and a lobulated shape (P = 0.006) significantly affected the morphologic assessment on 3D-TOF-MRA.

Conclusion: Three-dimensional TOF-MRA can accurately depict and display morphologic features of distal ICA UIAs. Tiny or giant-sized distal ICA aneurysms and with lobulation tend to carry a great risk of misdiagnosis in morphologic assessments.