Radial shear strain elastography imaging of carotid atherosclerotic plaques in a porcine model

The objective is to show the feasibility of shear strain elastography (SSE) in vivo with intravascular ultrasound (IVUS) radio-frequency (RF) data acquired at 20 MHz in carotid arteries of atherosclerotic pigs. We previously proposed the Lagrangian speckle model estimator (LSME) to estimate the strain tensor including the shear strain that could be involved in atherosclerotic plaque hemorrhage, inflammation and rupture mechanisms. However, the LSME performance to compute SSE had never been validated. Atherosclerotic pigs with significant plaques on carotids were studied. To induce atherosclerosis, pigs were put on an atherogenic diet and partial ligations of common carotid arteries were performed. Diabetes was induced by selective intra-arterial injection of streptozotocin. IVUS acquisitions were performed before sacrifice and histology analyses were realized on fixed dissected carotids. SSE maps at end diastole were estimated with a new implementation of the LSME and matching with histology sections was realized. SSE clearly identified all plaques with cohabitation of high positive and high negative shear values, and minimum shear elsewhere within the vessel wall. This study demonstrates the performance of the LSME implementation to estimate the shear strain distribution, and the feasibility of SSE to highlight atherosclerotic plaque vulnerability characteristics.