The Relationship Between Carotid Plaque on Magnetic Resonance Plaque Imaging and Time From Stroke Onset.

Introduction: Previous studies report that rate of recurrent stroke, as well as the risk of carotid surgery, is highest in the early stages following cerebral infarction and decreases over time, which suggests a process of plaque healing and stabilization. The purpose of this study is to identify differences in carotid plaque components according to the time from stroke onset, using carotid magnetic resonance plaque imaging (MRPI) to evaluate the dynamic phase of plaque development following an acute cerebrovascular ischemic event.Methods and Results: MRPI on 3T scanners was obtained in 128 patients enrolled in the Carotid Artery Stenting study (MRCAS). MRCAS is a non-randomized multicenter prospective observational study to compare the plaque characteristics evaluated by MRI and ischemic complications after CAS in Japan. Among the 128 subjects, 60 presented with TIA or stroke and 68 were asymptomatic. The 60 TIA/stroke cases were classified into four groups based on the interval from the onset of symptoms to the date of carotid MRPI (Group 1: <14 days [n=25]; Group 2: 15-30 days[n=13]; and Group 3: >31 days [n=22]). The 68 asymptomatic cases were classified as Group 4. The volume of intraplaque hemorrhage (IPH), necrotic core, calcification and loose matrix was quantified on MRPI using Radiant DICOM viewer. Further, the presence of inner Loose Matrix (iLM) was identified as a high intensity area located between the vessel lumen and necrotic core or IPH on both T2WI and proton density weighted images.Patients characteristics were not significantly different among all groups. The mean volume of loose matrix in Group 3 was significantly lower than Group 1 and Group 4 (0 mm3 vs 12.3 mm3 and 15.5 mm3; p= 0.01, 0.03, respectively). The prevalence of iLM in Group 1 was higher than in Group 3 and 4 (68% vs 18.2%, 38.3% ; p<0.01, <0.01, respectively). Conclusions: The prevalence of inner Loose Matrix, located at the interface between the lumen surface and the necrotic core or IPH, is significantly higher in the early stage after stoke/TIA. This study suggests that carotid plaques undergo rapid evolution, especially adjacent to the luminal surface, after an acute cerebrovascular ischemic event.