Characterization of plaque components with intravascular ultrasound elastography in human femoral and coronary arteries in vitro

Background-The composition of plaque is a major determinant of coronary-rel ated clinical syndromes. Intravascular ultrasound (IVUS! elastography has p roven to be a technique capable of reflecting the mechanical properties of phantom material and the femoral arterial wall. The aim of this study was t o investigate the capability of intravascular elastography to characterize different plaque components. Methods and Results-Diseased human femoral (n=9) and coronary (n=4) arterie s were studied in vitro. At each location (n=45), 2 IVUS images were acquir ed at different intraluminal pressures (80 and 100 mm Hg). With the use of cross-correlation analysis on the high-frequency (radiofrequency) ultrasoun d signal, the local strain in the tissue was determined. The strain was col or-coded and plotted as an additional image to the IVUS echogram. The visua lized segments were stained on the presence of collagen, smooth muscle cell s, and macrophages. Matching of elastographic data and histology were perfo rmed with the use of the IVUS echogram. The cross sections were segmented i n regions (n=125) that were based on the strain value on the elastogram. Th e dominant plaque types in these regions (fibrous, fibro-fatty, or fatty) w ere obtained from histology and correlated with the average strain and echo intensity. The strain for the 3 plaque types as determined by histology di ffered significantly (P=0.0002). This difference was mainly evident between fibrous and fatty tissue (P=0.0004), The plaque types did not reveal echo- intensity differences in the IVUS echogram (P=0.882). Conclusions-Different strain values are found between fibrous, fibro-fatty, and fatty plaque components, indicating the potential of intravascular ela stography to distinguish different plaque morphologies.