Carotid Plaque Characterization Using Innovative Ultrasound Techniques

Strokes are the second leading cause of disability and death worldwide (according to World Health Organization in 2019). They are ischemic in origin in 80% of cases. Atheromatous disease, and more specifically carotid stenosis, is responsible for 20% of these ischemic strokes. Current recommendations, based on high levels of evidence, consider only the degree of carotid artery stenosis to define the threshold for surgical treatment. However, it is now accepted that the composition and rate of progression of atherosclerotic plaque are also criteria to be considered when selecting patients at high risk of stroke. The presence of hemorrhage and a lipid core in the atheromatous plaque, both factors of instability, is associated with a greater risk of ipsilateral ischemic events. The presence of intraplaque hemorrhage is therefore a marker of plaque instability. In this context, techniques for in vivo analysis of atherosclerotic plaque composition need to be developed to better target patients for surgery. Ultrafast ultrasound enables imaging rates of several thousand images per second. Ultrasound Localization Microscopy (ULM) gives access to the vascular microstructure of tissues: the localization of injected microbubbles, which enhance the ultrasound signal in vessels, and the tracking of these microbubbles enable the vascularization of the tissue in question to be mapped. Ultrasound spectroscopy qualifies tissue microstructure: this operator- and system-independent technique is based on frequency analysis of ultrasound signals backscattered by tissue, and more specifically on analysis of the backscatter coefficient (BSC). Measuring the BSC is intrinsic to the tissue, and provides quantitative parameters on the scatterers to qualify the tissue. The study hypothesis is that these two ultrasound techniques will provide information on the characteristics of the atherosclerotic plaque: the presence of neovessels and biomarkers linked to its composition, including intraplaque hemorrhage.