An ultrasound-based approach for the characterization of fluid–structure interaction of large arterial vessels

Abstract

An ultrasound-based approach to characterize the fluid–structure interaction in large arterial vessels is presented. The ultrasound-based data are fed into a new dynamic model accounting for a two-dimensional (2D) stress state, which in turn provides a better estimate of the material elasticity under dynamic loading. In order to validate the semi-empirical model, a compliant, synthetic vessel was subjected to a range of pulsatile and steady flow profiles. Ultrasound imaging was used to capture the flow field through the compliant vessel and its change in diameter over time. Internal pressure was extracted from ultrasound image velocimetry using spatial integration of the Navier–Stokes equation, and used to find the pressure–area relationship. Two constitutive laws describing a one-dimensional expansion of a cylindrical vessel, the Laplace law and one from Olufsen (Am J Physiol-Heart Circul Physiol 276(1):H257–H268, 1999), were also used to estimate the instantaneous elastic modulus. A uniaxial tensile test of the vessel material was performed to provide validation criteria. Under steady flow, the Laplace law predicted the elasticity of the vessel material with 255% error and the results from Olufsen (Am J Physiol-Heart Circul Physiol 276(1):H257–H268, 1999) had an error of 99%. In contrast, our developed 2D stress model predicted the elasticity with less than 10% error. The Laplace law and the Olufsen (Am J Physiol-Heart Circul Physiol 276(1):H257–H268, 1999) model were revealed to be flow-dependent such that the trend of the resultant elastic modulus varied for each pulsatile flow case. However, the 2D stress model showed no flow dependency, presenting consistent elasticity results across all test cases.