Prediction of silent ischemic lesions after carotid artery stenting using integrated backscatter ultrasound and magnetic resonance imaging

Objective: A major concern with carotid artery stenting (CAS) is the potential for cerebral embolism. The purpose of this study was to determine whether integrated backscatter (IBS) ultrasound and black-blood magnetic resonance imaging (BB-MRI) can predict the risk of a silent ischemic lesion after CAS.

Methods: We performed quantitative analysis of plaque characteristics in carotid arteries using IBS ultrasound and BB-MRI before CAS in 50 patients. We measured IBS values and the signal intensity ratio (SIR) from T1 weighted images of all plaques. We also performed diffusion-weighted (DWI) MRI of the brain before and after CAS.

Results: In the patient group that was positive (n=19) for newly appearing ipsilateral silent ischemic lesions (NISIL), relative unstable component area (%UCA) evaluated by IBS analysis (60.2+/-23.4% and 35.3+/-19.2%, p<0.001) and SIR (1.40+/-0.19 and 1.18+/-0.25, p<0.01) in most stenotic lesions were higher than in the NISIL-negative group (n=31). From the analysis of receiver operating characteristic curves, 50% of the %UCA measured by IBS and an SIR of 1.25 measured by BB-MRI were the most reliable cutoff values for predicting NISIL. In multivariate logistic regression analysis, the independent predictors of NISIL were SIR (p=0.030), the CRP level (p=0.041) and the %UCA measured by IBS (p=0.049).

Conclusions: Quantitative tissue characterization of carotid plaques using IBS ultrasound and BB-MRI was useful to predict NISIL after CAS. The plaque components in carotid arteries should be evaluated by BB-MRI or IBS ultrasound before CAS to improve the clinical outcome of this procedure.