Phonoangiographic Diagnosis of Stenosed Arteries: A Computational Fluid Flexible-Structure Acoustic Interaction Study

The present article is on pulsatile hemodynamics-induced sound-based diagnosis of stenosis in compliant arteries of three types: Coronary, carotid, and femoral. Considering axisymmetric stenosis in straight arteries along with clinically observed dimensions of the arteries and enveloping tissue, the present numerical study considers blood as a Newtonian fluid and both artery and tissue as isotropic and geometrically nonlinear (materialistically linear) solid. For the physiological fluid flexible-structure acoustic interaction (FfSAI) study, an in-house multiphysics solver is used for a parametric study—using various stenosis level $S$ (60%, 70%, and 80%) and stenosis length $L_{\mathrm{st}}$ (2D and 4D); for each of the arteries. With increasing $S$, an increase in acoustic acceleration's FFT spectrum-based cut-off frequency $f_c$ is found—indicating possibility of quantitative phonoangiographic diagnosis. The variation of this frequency $f_c$ with $S$ follows similar trend as that of frequency calculated by pressure fluctuation's FFT spectrum, thus correlating the hemodynamics as the cause for generation of the sound/bruits. Also, a flow-visualization-based frequency, which is calculated using vortex length and velocity during vortex dissipation stage, matches reasonably (≤ 15% difference) with the cut-off frequency of pressure fluctuation. For the first time in the literature, our sound velocity level-based study shows over-prediction of stenosis by neglecting flow-induced tissue deformations. This implies the importance of modeling structural flexibility, along with flow and acoustics while developing a computational Point-of-Care diagnostic tool. Finally, using analytical method for acoustics, a computationally efficient semi-analytical FfSAI approach is proposed. The present work is significant since an accurate and computationally efficient framework and flow-physics-based analysis are presented for phonoangiographic diagnosis of stenosed arteries of three types.