Why is middle cerebral artery plaque augmented by contrast media? A phantom study using middle cerebral artery stenotic silicon model

Purpose: The pathophysiologic mechanisms of contrast enhancement (CE) of middle cerebral artery (MCA) plaque remain unclear since histologic and imaging findings have never been compared. The purpose of this study was to assess the pattern of CE between patients with MCA stenosis or occlusion and in an MCA stenotic silicone model. Methods: We retrospectively reviewed black blood (BB) contrast-enhanced T1-weighted (CE-T1W) imaging of patients who presented with acute stroke symptoms between January 2017 and January 2018. We subdivided the enrolled subjects according to whether the cerebral angiography findings suggested stenosis or occlusion. Silicone models were made with 4 degrees of MCA stenosis (stenotic area: 0.8 mm, 1.0 mm, 1.2 mm, and 1.4 mm) with a 3-mm lumen. BB CE-T1W imaging on silicone models with stenosis was obtained 5 min after contrast injection. Results: During the period of this study, 19 patients with complete MCA occlusion and 22 with MCA stenosis, as shown by the cerebral angiography, were enrolled in this study. The CE of the silicone models with stenosis were 0.8 (74%) mm and 1.0 (66.7%) mm. The SI ratios of the CE of the plaque and the lumen were similar between the silicone models and the MCA stenosis/occlusion groups (silicone models: 31.0 ± 11.2; MCA occlusion: 27.6 ± 19.6; MCA stenosis: 22.8 ± 9.8). Conclusion: The silicone stenotic MCA model was characterized by luminal enhancement through contrast stagnation. The findings of the CE of the MCA plaque may be partially associated with stagnation of the contrast media.