High-intensity vessel sign on fluid-attenuated inversion recovery imaging: a novel imaging marker of high-risk carotid stenosis—a MRI and SPECT study

Background: Measurement of luminal stenosis and determination of plaque instability using MR plaque imaging are effective strategies for evaluating high-risk carotid stenosis. Nevertheless, new methods are required to identify patients with carotid stenosis at risk of future stroke. We aimed to clarify the mechanisms and clinical implications of the hyperintense vessel sign (HVS) as a marker of high-risk carotid stenosis. Methods: We included 148 patients who underwent carotid stent (CAS) or carotid endarterectomy (CEA). MRI FLAIR was performed to detect HVS prior to and within 7 days after CAS/CEA. MR plaque imaging and ¹²³I-iodoamphetamine SPECT was performed prior to CEA/CAS. Detailed characteristics of HVS were categorized in terms of symptomatic status, hemodynamic state, plaque composition, and HVS on time series. Results: Forty-six of 80 symptomatic hemispheres (57.5%) and 5 of 68 asymptomatic hemispheres (7.4%) presented HVS (P ' 0.01). Of the 46 symptomatic hemispheres with HVS, 19 (41.3%) presented with hemodynamic impairment and 27 (58.7%) presented without hemodynamic impairment. Of 19 hemispheres with hemodynamic impairment, 12 subjects (63.2%) showed high intensity and 7 (36.8%) showed iso-intensity plaques on T1WI. All 27 hemispheres without hemodynamic impairment showed high-intensity plaques. Of the five asymptomatic and HVS-positive hemispheres, one showed hemodynamic impairment; MR plaque imaging revealed T1 iso-intensity. The other four hemispheres that did not show hemodynamic impairment showed T1WI high-intensity plaques. Conclusion: There are two possible mechanisms of HVS, hemodynamic impairment due to severe carotid stenosis and micro-embolism from unstable plaques. HVS could be a radiological marker for high-risk carotid stenosis.