Discovery of the ring resonant frequency for noninvasively estimating local elastic modulus of arterial wall

Abstract

Increased stiffness of arteries has recently gained acceptance as an independent risk factor for cardiovascular and many other diseases. Pulse wave velocity (PWV) is widely used for estimating the stiffness of an artery. However, PWV is an average indicator of artery stiffness between the two measuring points, and therefore does not identify local stiffness. In addition, the thickness of the artery is needed to calculate artery elastic modulus. We have discovered that there is a series of ring resonant frequency in arteries that can be used for estimating local arterial elastic modulus. These resonances can be excited by remote palpation with selectively placed ultrasonic radiation force. Experiments on ring resonance were carried out on an excised artery as well as a rubber tube. This family of resonances occurs at relatively low frequency, around 356 Hz for the artery. Estimation of the Young’s modulus is 135 kPa by the ring frequency 356 Hz without the requirement of the arterial thickness. The estimated modulus is very consistent with the other ring resonant frequency measurements. The theory of ring resonance is developed and verified with the rubber tube experiments.