Composition Analysis And Classification Of Carotid Atherosclerotic Plaque With 3.0T MRI

Objective:To evaluate the value of 3.0T high resolution MRI in differentiating carotid atherosclerotic plaque composition, determining plaque type, and predicting plaque stability.Materials and Methods:Thirty three consecutive patients with carotid atherosclerotic plaques which admitted in neuro-medicine department were collected in the study group from June 2013 and December 2014.All the patients were scanned using GE 3.0T MRI after informed consents were obtained.The standardized protocols include three-dimensional time-of-flight (3D-TOF),double-inversion recovery Ti weighted image,T2 weighted image,proton density weighted image,enhanced-T1 weighted imageand carotid artery MRA.The scan field of view covered the distal part of common carotid artery, its bifurcation,and proximal part of internal carotid artery with a total length of 2cm.Image analyzing were focused on plaque composition such as lipid rich necrotic core, intraplaque hemorrhage, thrombosis, calcification in the plaque and fibrous cap condition as well at previous mentioned 3 locations (CCA, CA and ICA). Carotid atherosclerotic plaque classification was based on criteria of American Heart Association (AHA). Fisher’s exact test were performed, P<0.05 was considered as statistically significant. All carotid atherosclerotic plaques were divided into stable plaque group and unstable plaque group, and both groups were compared with chi-square test in terms of lipid necrotic core,hemorrhage, thrombosis,calcification and fibrous cap surface state(complete or broken).Measuring The lipid core and Intraplaque hemorrhage volume and Calculating the proportion of plaque volume to evaluate the significance of lipid core size in diagnosis of unstable plaques,and to look for the best diagnostic threshold of Intraplaque hemorrhage volume percent in determining plaque nature with ROC curve analysis.Results:1、plaque type distribution at 3 different locations of carotid arteryTotal 63 carotid atherosclerotic plaques were found in 33 patients. According to American Heart Association classification, type Ⅰ-Ⅱ plaques accounts for 12.7% of total plaques, type Ⅲaccounts for 27% of total, type Ⅳ-Ⅴtogether occupies 19% of them, type VI with number of 31.8% is the biggest in the group, and type Ⅷ accounts for 9.5%. There was no statistical significant difference for plaque location (Fisher’s exact test:P=0.016).2、Comparison of plaque compositions between stable plaque group and unstable plaque groupA total of 63 plaques includes 5 lipid rich necrotic core,4 hemorrhage,0 thrombosis,7 calcification,2 ruptured fibrous cap in stable plaque group,and includes 26 lipid rich necrotic core,11 hemorrhage,8 thrombosis,3 calcification,12 ruptured fibrous cap in unstable plaque group.There was statistical significant difference (P<0.05)between stable plaque group and unstable plaque group in terms of the occurrence rate of lipid rich necrotic core, hemorrhage, thrombosis and integrity of fibrous cap. No significant differences(P> 0.05) were found for the number of calcification between the two groups.3、ROC curve analysis of Intraplaque hemorrhage volume percent31 stable plaques as control group,32 unstable plaques as case group,The ROC curve analysis of Intraplaque hemorrhage volume percent shows that the area under curve is 0.630,95%confidence interval is(0.517,0.748),there was statistical significance(P=0.0130<0.05),16.7% is considered as the best diagnostic threshold with a sensitivity of 34.88%,and a specificity of 100%.Conclusion:3.0T MRI can identify and distinguish plaque compositions, determine plaque type and identify plaque compositions between table plaque group and unstable plaque group. It can be an important guidance for treatment option and outcome evaluation.