Assessment of the hyper-viscoelastic behavior of aorta phantoms from ultrasound images

International audienceThis work was carried out within a research project aiming to produce replicas (or phantoms) representing the mechanical behavior of the cardiovascular system as faithfully as possible. Healthy vessels as well as vessels suffering from pathologies should be considered. Various applications of these phantoms can be forecast: repeating surgical procedures before real interventions (including the effect of blood flow), validation of the medical image processing algorithms, assistance in modeling viscoelastic behavior of real tissues ... Specifically, the aim of this work was to validate a method for characterizing the hyper-viscoelastic behavior of silicone tubes by measuring the deformation (Inflation-Extension) using a medical imaging method (ultrasound) while the periodic blood flow is simulated in the tube. This is achieved by inserting the tube in a water circuit where the pressure is controlled to simulate the blood pressure. This circuit is itself immersed in a water bath for transmitting ultrasonic waves. The system was validated by showing that the hyper-viscoelastic behavior measured by this way was consistent with that determined by standard methods such as tensile tests and dynamic mechanical analysis. Diverse silicone formulations, exhibiting behaviors covering the range of those of real arterial tissues, were thus tested. Their behaviors were described on the basis of hyper-viscoelastic model constituted of several Maxwell elements in parallel with a hyperelastic branch (Yeoh model). Eventually, this method can be adapted to determine the hyper-viscoelastic behavior of real blood vessel walls by a non-invasive method based on medical imaging. Hence, it would be helpful to diagnose or predict pathologies affecting the hyper-viscoelastic behavior of the arterial wall