Excitation and measurement of flexural waves in arterial vessels

Pulse wave velocity in an artery is a very important indicator of the stiffness and disease of the artery. The pulse wave velocity is directly related to the Young´s modulus in the circumferential direction of the artery by the well known Moens-Korteweg equation. Pulse wave velocity in an artery is measured with the standard pulse delay technique. However, the precise timing of the pressure wave is difficult due to the presence of reflected waves. In this paper we propose to excite flexural waves in an artery by low frequency localized radiation force ultrasound. These waves can be measured very accurately over a short distance. Experimental studies were carried out on a pig carotid artery in gelatin. The flexural wave speed was measured by the phase change at a known distance for a given frequency. Velocity dispersion was found for the flexural wave. This is very important because the Moens-Kertowag equation does not consider dispersion. Viscoelastic properties of the artery were also measured and discussed. The present technique offers a new tool for measuring wave speed in arterial vessels.