Computational Hemoacoustic Investigation for Phonoangiography-Based Rupture Prediction in Compliant Fusiform...

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 ( $u_r^{\text{'}}$ ) and rupture potential index ( $\mathrm{RPI}$ ) are calculated for different configurations. A significant 71% increase in cutoff frequencies of skin-surface acoustic velocity $u_r^{\text{'}}$ 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 $u_r^{\text{'}}$ 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.