Computational Hemoacoustic Investigation for Phonoangiography-Based Rupture Prediction in Compliant Fusiform Abdominal Aortic Aneurysm

Abstract

For sound signal-based diagnosis and rupture prediction of abdominal aortic aneurysms (AAA), this study performs a physiological fluid flexible-structure acoustic interaction (FfSAI) analysis for pulsatile blood-flow using an in-house solver. The presence of murmurs is computationally presented for the first time using a qualitative indicator of the acoustic signal. A pulsatile Newtonian blood-flow at the inlet, with Womersley number $\mathrm{Wo}$ = 16.5, is considered. For a fusiform (axisymmetric) AAA, a parametric FfSAI study is presented with various height ($H$) to diameter ($D$) ratios $H/D$ = 0.3, 0.5, 0.7, 1.0, and 1.2, and width ($W$) to diameter ($D$) ratios $W/D$ = 0.5 and 1.0. Vertical skin-surface velocity ($u_r^{\prime }$) and rupture potential index ($\mathrm{RPI}$) are calculated for different configurations. A significant 71% increase in cutoff frequencies of skin-surface acoustic velocity $u_r^{\prime }$ is found with the variation of $H/D$ from 0.3 to 1.2—indicating phonoangiography-based diagnosis as well as distinction of aneurysm levels. The proposed CFD-based flow-visualization indicates a vortex impingement on the aneurysm wall as the primary cause of high cutoff frequencies in the acoustic spectrum. A correlation is proposed to calculate rupture-risk through frequency data based on $\mathrm{RPI}$ and $u_r^{\prime }$ spectrum. The decibel values predicted by neglecting structural flexibility over-predict the bulge level ($H/D\ge$1)—emphasizing the importance of arterial compliance in a computational study. This work establishes the efficacy of phonoangiography-based diagnosis in assisting medical practitioners with treatment planning and underscores the necessity of using an elastic model for structure.