Abstract
Background: Evaluation of intracranial atherosclerosis currently relies on angiography techniques to detect luminal stenosis, among which 3D time-of-flight (TOF) MRA is most widely used. Recently, 3D vessel wall (VW) MRI has allowed direct plaque visualization in major intracranial arteries. Purpose: We sought to study the association between luminal stenosis on TOF-MRA and plaque on VW-MRI in major intracranial arteries. Methods: Patients with recent cerebral ischemic events and without cardioembolic or rare etiologies were scanned with intracranial TOF-MRA (resolution: 0.53x0.83x1.4 mm 3 ) and VW-MRI (0.8x0.8x0.8 mm 3 ). Eleven segments were evaluated, including cavernous and supraclinoid internal carotid artery (ICA), anterior cerebral artery (A1), middle cerebral artery (M1), basilar artery, and posterior cerebral artery (P1). TOF-MRA and VW-MRI were analyzed blinded to each other and clinical data. Luminal stenosis on TOF-MRA was categorized as mild (1-49%), moderate (50-69%), severe (70-99% or flow void), and occlusion (100%). Plaque on VW-MRI was defined as focal wall thickening that exceeded twice reference wall thickness, with plaque burden measured as 1 - lumen diameter / outer wall diameter at the level of maximum wall thickness. Results: Nineteen patients were recruited (59.4±14.3 years; 68.4% male). TOF-MRA detected stenosis in 28 segments while VW-MRI detected plaque in 88 segments. Sixty-three (71.6%) plaques on VW-MRI did not show luminal stenosis on TOF-MRA, which, compared to those showing luminal stenosis on TOF-MRA, had smaller plaque burden (0.48±0.09 vs. 0.58±0.11; p<0.001) and were more commonly localized in the supraclinoid ICA (p=0.029) and less likely in the A1 segment (p=0.043). Three (2 mild; 1 moderate) stenoses on TOF-MRA did not show plaque on VW-MRI. TOF-MRI and VW-MRI had a weak correlation both in detecting segmental atherosclerosis (Cohen’s kappa: 0.30 [0.20, 0.41]) and in evaluating lesion severity (stenosis vs. plaque burden; Spearman’s rho: 0.44 [0.25, 0.60]). Conclusions: In symptomatic patients, segmental atherosclerosis was three times more prevalent on VW-MRI than TOF-MRA. Further studies are warranted to understand the clinical implications of VW-MRI plaques that are undetected on TOF-MRA.
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