Measurement of Shear Wave Propagation and Investigation of Estimation of Shear Viscoelasticity for Tissue Characterization of the Arterial Wall

Purpose: The aim of this study was to find an array of frequencycomponents, ranging from 0 Hz (direct current) to several tens of hertz that comprise the small vibrations on the arterial wallusing noninvasive in vivo experiments. These vibrations are caused mainly by blood flow. The viscoelasticity of the arterial wallwas estimated from the frequency characteristics of these vibrations propagating from the intima to the adventitia. Methods: Propagation of these frequencies in human tissue displays certain frequency characteristics. Based on the Voigt model, shear viscoelasticity can be estimated from the frequency characteristics of the propagating vibrations. Moreover, we estimated shear viscoelasticity from the measured frequency characteristics of shearwave attenuation. Results: Shear wave propagation from the intima to the adventitia resulting from blood flow was explained theoretically based on the obtained measurements. Shear viscoelasticity was also estimated from the measured frequency characteristics of shear wave attenuation. Conclusions: Based on the proposedmethod, shear viscoelasticity can be estimated from ultrasonographic measurements. These results have a novel potential for characterizing tissue noninvasively.