Advanced imaging and cavitation bubbles as promising tools for hemodynamic disorders diagnosis and treatment

Hemodynamic disorders encompass all anomalies occurring within blood vessels that disrupt the normal blood flow. Detecting these pathologies, assessing their severity, and evaluating the benefit-risk balance of associated treatments are essential for refining medical decision-making. In this context, the precise measurement of key parameters related to specific pathologies, as well as the understanding of physical phenomena involved in various endovascular intervention techniques and their complications, is of major importance. To this end, we use phase-contrast magnetic resonance imaging (PC-MRI), regarded as gold standard tools for quantifying hemodynamic parameters. Specifically, we leverage the high signal-to-noise ratio of ultra-high-field 7â ¯T MRI, recently introduced in clinical practice, to substantially enhance image spatial resolution, enabling the visualization of flow characteristics with unparalleled details and the assessment of velocity-field-derived parameters that strongly depend on spatial resolution, such as wall shear stress (WSS), a key factor implicated in numerous cardiovascular diseases. To ensure accurate in vitro PC-MRI flow measurements, we focus on eliminating mechanical resonance phenomena inherent to the hydraulic circuits used in this type of experiment, which would otherwise compromise the reproduction of physiological flows. We demonstrate that a compliance chamber, optimally placed at the outlet of the vascular model and of sufficient capacity, effectively overdamps the systemâ s first eigenmode, enabling faithful reproduction of pulsatile flow waveforms. Then, we measure near-wall hemodynamic parameters in silicone aneurysm models and show that the high spatiotemporal resolution arising from 7T PC-MRI enables to resolve high and low WSS patterns in an unprecedented way. Next, to better understand the physical mechanisms of ablation and collateral damage caused by cavitation bubbles during laser-assisted endovascular surgeries, we investigate their dynamics using high-speed imaging in two scenarios. First, we examine the dynamics of cavitation bubbles near the vibrating antinode of a low amplitude vibrating plate, analysing the influence of the stand-off distance, the plateâ s resonance frequency, and the bubble seeding phase, and compare these results to the well-established case of a bubble near a rigid surface. We show that bubble dynamics is strongly influenced by the instantaneous pressure and pressure gradient generated by plate motion, with the former capable of increasing the micro-jet velocity up to 145% and reducing the centroid displacement up to 38% compared to the rigid reference case. Then, we analyse the dynamics of cavitation bubbles inside elastic tubes designed to mimic the properties of arteries. We study the influence of ambient pressure, bubble size, and tube dimensions and stiffness on the behaviour of bubbles and tubes. We mainly demonstrate that the bubble motion is always in phase with