Elastosonography as an ultrasound tool to characterize and quantify plaque stiffness

Background: Since the last 30 years, plaque texture characterization with ultrasound has become reliable and consistent with vulnerable plaques identification, along with the degree of stenosis. “Hard” hyperechoic plaques, predominantly composed of collagen or calcium, are indeed at lower embolic risk than “soft” hypoechoic plaques containing atheroma debris, lipids and intraplaque hemorrhage. Elastography is a recently new technique able to determine tissue stiffness and mostly applied for breast, thyroid, prostate glands and, recently, also for carotid plaques. The principle is based on the compression of tissue with ultrasound pulses that generates shear waves propagating within the tissue at a measurable velocity and correlated with the tissue stiffness. We describe a sample study carotid plaques imaging with Elastography. Material and Methods: Shear‐Wave elastography (Virtual Touch IQ, Siemens S2000) was used to present images of 30 heterogeneous carotid plaques, of different echogenicity. According to the elastographic image presentation, stiffness data (velocity measurements) were calculated in manually selected areas of different echogenicity and correlated with the GSM values calculated in the same areas. Results: Elastography was easily, quickly feasible and reproducible in 28/30 patients, with imaging limitations related to the strong acoustic shadows in highly calcified plaques. Plaque presentation with elastography images allowed a good visualization of the different areas of the heterogeneous plaques, allowing measurements of the shear wave velocity in the different echogenic regions. Shear wave velocities were directly related to the GSM values, with shear velocities lower than 4 m/sec in low GSM (<30) areas. Conclusions: Elastography of carotid plaques helps to determine plaque stiffness, with the ability to easily visualize and quantify differences in the plaque tissue elasticity. Further studies will correlate the usefulness of stiffness quantification with plaque vulnerability and stroke risk.