The ARFI derived data and the QUS derived data will be combined with clinically available measures currently used for diagnosis of carotid stenosis to form the input parameters for the algorithm. In order to train and test the algorithm the plaque removed during CEA procedure will be collected and the histology slides prepared from these plaques will be analyzed for the same regions where ARFI and QUS data were collected. This histology review provides the 'gold' standard for training and testing the algorithm. The majority of these matched sets (75%) will be used for training the algorithm. While the remainder (25%) will provide a test of the accuracy of the algorithm for these types of matched data. The sensitivity and specificity for each tissue type defined during the histology review will be reported.