High intensity signal in the plaque on routine 3D-TOF MRA is associated with ischemic stroke in the patients with low-grade carotid stenosis

Background and purpose: Carotid artery stenosis is one of the major causes of ischemic strokes. However, degree of stenosis is not always correlated with frequency of ischemic strokes. The aim of this study was to evaluate relationships between high intensity signal (HIS) in the carotid plaques on maximum intensity projection (MIP) images detected by routine three-dimensional time-of-flight magnetic resonance angiography (3D-TOF MRA) and ischemic strokes in the patients with low-grade stenosis. Methods: One hundred fifty two patients with low-grade carotid artery stenosis (30%-49%) were included. The presence of HIS located in the plaque but having no connection to the lumen in all projections on MIP images of 3D-TOF MRA was defined as HIS-positive using the previously reported criteria. We analyzed the relationship between the presence of HIS and prior ischemic strokes. Results: Prior ipsilateral ischemic strokes were observed more frequently in HIS-positive group (12 of 56, 21.4%) than HIS-negative group (1 of 96: 1%) (p < 0.001). In multivariate logistic regression analysis, the presence of HIS (odds ratio: 31.8, 95% confidential interval (CI): 3.81-264, p = 0.001) and hyperlipidemia (odds ratio: 10.45, 95% CI: 1.01-13.4, p = 0.048) were independent determinants of prior ischemic strokes after adjustment for age. Conclusions: HIS in plaques on MIP images of 3D-TOF MRA was an independent determinant of prior ischemic strokes.