An Inverse Method to Determine Arterial Stiffness with Guided Axial Waves

Many cardiovascular diseases can alter arterial stiffness; therefore, measurement of arterial wall stiffness can provide valuable information for both diagnosis of such diseases in the clinic and evaluation of the effectiveness of relevant drugs. However, quantitative assessment of the in vivo elastic properties of arterial walls in a non-invasive manner remains a great challenge. In this study, we found that the elastic modulus of the arterial wall can be extracted from the dispersion curve of the guided axial wave (GAW) measured using the ultrasound elastography method. It is shown that the GAW in the arterial wall can be well described with the Lamb wave (LW) model when the frequency exceeds a critical value f_c, whose explicit form is determined here based on dimensional analysis method and systematic finite-element simulations. Further, an inverse procedure is proposed to determine both f_c and the elastic modulus of the arterial wall. Phantom experiments have been performed to validate the inverse method and illustrate its potential use in the clinic.