Modal analysis of ultrasound radiation force generated shear waves on arteries.

Arterial elasticity has gained importance in the past few decades as a predictor of cardiovascular diseases and mortality. Measuring the speed of propagation of the pressure wave traveling in the wall of the arteries has been used for a very long time to estimate the mechanical properties of the artery. Two of the major disadvantages of this method are the low temporal resolution (1 sample per second) and the low spatial resolution (carotid-femoral or carotid-radial segments). In our laboratory, we have been working on an ultrasound radiation force-based method to generate high frequency local shear waves, which will allow the study of the mechanical properties of short arterial segments within the heart cycle. In this work we present a modal analysis of the waves generated by our method on an excised pig artery. By doing a two-dimensional fast Fourier transform (2D FFT) of the propagating waves, it was possible to differentiate the multiple Lamb-like modes propagating in the wall. These modes showed changes with varying transmural pressure; this was expected as the arterial stiffness increases with pressure. This work shows the feasibility of our method for the study and characterization of propagating modes in the arterial wall. Future studies include developing a Lamb wave model for cylindrical viscoelastic structures to fit our data.