Abstract 7: Higher Prevalence of High-t1w-signal Plaques on the Symptomatic Side in Patient with Recent Ischemic Stroke

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Introduction: Inversion-recovery prepared variable-flip-angle 3D FSE (IR-SPACE) was recently proposed as a whole-brain vessel wall MRI method to assess intracranial vessel wall (IVW) abnormalities. Compared with conventional SPACE or 2D FSE, it provides more heavily T1 weighted (T1w) contrast that, based on extensive research on carotid atherosclerosis, is highly sensitive to vulnerable atherosclerotic plaque features - intraplaque hemorrhage and inflammation. It was hypothesized that, using the new approach, the prevalence of HT1S plaques is higher in the symptomatic side in patients with recent anterior circulation ischemic stroke.Methods: From Oct 2015 to Aug 2016, 33 patients with ischemic stroke (<14 days) and an intracranial stenosis of > 50% were consecutively recruited. The MRI protocol included regular brain MRI and intracranial MRA followed by pre- and post-contrast IR-SPACE. After excluding those with nonatherosclerosis etiology (5) and uninterpretable images (3), 25 patients were available for image review by two independent blind readers. Plaques defined as eccentric wall thickening with or without luminal stenosis were first identified and were then categorized as either hyper-intense or iso-intense using adjacent normal vessel wall for reference.Results: In 25 patients, 65 plaques were identified, with 40 and 25 at the symptomatic and asymptomatic side, respectively. HT1S was shown in 32 plaques on pre-contrast IR-SPACE and in 23 plaques on post-contrast IR-SPACE on the symptomatic side, with 22 plaques in both scenarios. On the asymptomatic side, the incidence of HT1S was lower (i.e. 7 on pre-contrast, 4 on post-contrast, 1 in both).Conclusion: In the current study, IR-SPACE revealed higher prevalence of HT1S in the symptomatic side. Pre-contrast scans identified more HT1S plaques than post-contrast scans, and almost all (22/23) of these HT1S plaques shown on post-contrast images also demonstrated HT1S feature on pre-contrast images. Further classification of these HT1S plaques according to the likelihood to cause stroke will help elucidate the clinical relevance of the above findings and this analysis is underway.

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