Numerical simulations of ultrasound-induced deformation of the lung surface

Abstract

Ultrasound-induced lung hemorrhage remains the only known bioeffect of non-contrast, diagnostic ultrasound (DUS) found to occur in mammals. However, a fundamental understanding of the ultrasound-lung interaction is still lacking. In this study, we numerically simulate the deformation of the lung surface when subjected to clinically relevant pressure waves. We model the lung as air and the surrounding tissue as water. The two-dimensional, compressible Navier-Stokes equations are solved using a high-order accurate finite volume scheme. We first consider an air-water interface with a small sinusoidal perturbation and study the growth of the perturbations when subjected to a planar waveforms consisting of a step change in pressure. Scaling laws relating the waveform properties to the interface deformation rate are proposed for this simple case. Simulations with DUS waveforms indicate that the interface deformation depends on the unsteady nature of the wave. Preliminary analysis suggests that the initial interface deformation is driven by baroclinic vorticity deposited along the perturbed interface, and that the resulting stresses and strains are a possible candidate causing bioeffects.