Comparison between Quantitative Stiffness Measurements and Ultrasonographic Findings of Fresh Carotid Plaques

Using a stiffness meter, we quantitatively measured the stiffness of fresh plaques that had been excised by carotid endarterectomy. The objective of this study was to clarify the correlation between plaque stiffness and pre-operative carotid ultrasonographic findings, and predict the stiffness of plaques before surgery by comparison with the stiffness of common items. The study population comprised 44 patients (44 lesions) who had undergone carotid endarterectomy at our institution between December 2009 and October 2014. The stiffness of excised fresh plaques was measured using a stiffness meter and compared with the pre-operative echographic findings for the plaques and the stiffness of selected foods and common items. The mean stiffness value for all plaques was 4.52 ± 3.30 MPa (mean ± standard deviation). The plaques exhibiting calcification were significantly harder (p = 0.001). On classification of lesions on the basis of echographic findings, plaque hardness was in the order low-echoic (15 lesions) < iso-echoic (20 lesions) < high-echoic (9 lesions) (p = 0.02). The stiffness of the low-echoic group was equivalent to that of tofu or sliced cheese, whereas the plaques in the iso- and high-echoic groups exhibited stiffness similar to that of ham and a plastic eraser, respectively. A significant correlation was observed between the quantitative stiffness values of carotid plaques and their brightness on carotid ultrasonography. Using these data, operators might be able to predict plaque stiffness from pre-operative echographic findings. In addition, it might be useful for operators to compare such quantitative stiffness measurements with stiffness data for foods and common items to gain an understanding of the state of the target plaque before treatment.