Stefan Catheline - LabTau (Lyon)

Elastography, sometimes referred as seismology of the human body, is an imaging modality now implemented on medical ultrasound systems, on MRI and recently in optical coherence tomography devices. It allows to measure shear wave speeds within soft tissues and gives a tomography reconstruction of the shear elasticity. Elastography is thus a palpation tomography. It is also an efficient tool to visualize in situ and to study elastic wave propagation in soft materials such as foams, tubes and membrane.
Understanding the wave physics of porous material has important implication in human soft tissues where liquid is present, as blood for instance. We report experimental observation of a slow (few meters per second) compression wave within a foam.
Elastography experiment in a soft tube is also of interest. The pulse wave that can be felt with fingers along arteries is known to be an indicator of the cardiovascular health of a patient. But the physics of propagation of these guided waves still have secrets that will be discussed during this presentation.
The last part is devoted to elastography of membranes. Elastic membranes are often used as didactic demonstration of gravitation from the general relativity perspective. Indeed, trajectories of rolling spheres such as billiard balls influence each other through the deformation their mass print within the membrane tissue as would the space-time curvature of gravity. The analogy is pushed here using membrane waves. This allows revisiting through membrane waves, the famous 1919 Eddington experiment that demonstrated light deviations of stars in the vicinity of the sun.