Elucidation of viscoelasticity of common carotid artery from time series echograms recorded by high-frame-rate echography

The authors visualized the elasticity and viscosity of the common carotid artery noninvasively. The elastic index was calculated from the instantaneous velocity of the artery wall and continuous blood pressure. The instantaneous velocity was calculated from processing time series echograms recorded by high-frame-rate echography. Blood pressure was measured by a noninvasive sphygmomanometer using a cuff wound on the arm. The transition of velocity was related to blood pressure. Drawing pressure-velocity curve, elasticity and viscosity of carotid artery could be classified from the shape of the curve. In a young elastic artery, the curve was revealed to be similar to a circle. In a proportion of older arteries, the shape of the curve became flattened out. From the amplitude ratio of pressure and velocity, the elasticity and viscosity of an artery could be estimated.