C arotid artery atherosclerosis is one of the important causes of ischemic stroke. The efficacy of carotid endarterectomy (CEA) for severe symptomatic stenosis of the carotid artery has been demonstrated in several multicenter, randomized, clinical trials. 7,8,18 Currently, the therapeutic approach for preventing future ischemic events, including CEA, carotid artery stenting (CAS), and medical treatment, is decided primarily based on the percentage of luminal narrowing of the vessel. However, it has been shown that thromboembolic mechanisms correlate strongly with ischemic events in carotid artery stenosis. 16,36 Thus, a method for evaluating the risk of thromboembolism might improve the ability to identify the actual high-risk patients who would benefit most from intervention. In recent studies, some investigators have reported that plaque with a lipid-rich necrotic core aBBreViatiONS BB = black blood; CAS = carotid artery stenting; CE = contrast enhanced; CEA = carotid endarterectomy; ERR = expansive remodeling ratio; ICA = internal carotid artery; IPH = intraplaque hemorrhage; rSI = relative plaque signal intensity; VD = vessel diameter. OBJectiVe Plaque characteristics and morphology are important indicators of plaque vulnerability. MRI-detected intraplaque hemorrhage has a great effect on plaque vulnerability. Expansive remodeling, which has been considered compensatory enlargement of the arterial wall in the progression of atherosclerosis, is one of the criteria of vulnerable plaque in the coronary circulation. The purpose of this study was risk stratification of carotid artery plaque through the evaluation of quantitative expansive remodeling and MRI plaque signal intensity. methOdS Both preoperative carotid artery T1-weighted axial and long-axis MR images of 70 patients who underwent carotid endarterectomy (CEA) or carotid artery stenting (CAS) were studied. The expansive remodeling ratio (ERR) was calculated from the ratio of the linear diameter of the artery at the thickest segment of the plaque to the diameter of the artery on the long-axis image. Relative plaque signal intensity (rSI) was also calculated from the axial image, and the patients were grouped as follows: Group A = rSI ≥ 1.40 and ERR ≥ 1.66; Group B = rSI < 1.40 and ERR ≥ 1.66; Group C = rSI ≥ 1.40 and ERR < 1.66; and Group D = rSI < 1.40 and ERR < 1.66. Ischemic events within 6 months were retrospectively evaluated in each group. reSultS Of the 70 patients, 17 (74%) in Group A, 6 (43%) in Group B, 7 (44%) in Group C, and 6 (35%) in Group D had ischemic events. Ischemic events were significantly more common in Group A than in Group D (p = 0.01). cONcluSiONS In the present series of patients with carotid artery stenosis scheduled for CEA or CAS, patients with plaque with a high degree of expansion of the vessel and T1 high signal intensity were at higher risk of ischemic events. The combined assessment of plaque characterization with MRI and morphological evaluation using ERR might be useful in risk stratification for carotid lesions, whic...