Passive elastography: Extracting mechanical properties of soft tissues from natural elastic waves

Clinical devices that give elastography imaging from a shear wave speed measurement within tissues uses controlled sources for elastic wave generation. It can be a mechanical vibrator for transient elastography and magnetic resonance elastography (MRE) or ultrasound radiation pressure for ARFI and shear wave elastography technique. Generally speaking, the main drawback of all these methods is the drop of efficiency for deep regions and obese patient. Delivering robust elastic waves in depth is an issue. We have proposed in the past a solution that avoid the problem of shear wave penetration using active sources. It consists in using natural shear waves that exist everywhere in living tissues. These natural shear wave are created thanks to heart beating, to pulse wave within arteries or to muscle activities. Since a few years now, we have been tracking natural shear waves in different soft tissues of the human body and we have not yet been disappointed. Using uncontrolled shear wave needs a change in the group velocity measurement paradigm. This approach is the so-called noise correlation technique developed in the field of seismology.Clinical devices that give elastography imaging from a shear wave speed measurement within tissues uses controlled sources for elastic wave generation. It can be a mechanical vibrator for transient elastography and magnetic resonance elastography (MRE) or ultrasound radiation pressure for ARFI and shear wave elastography technique. Generally speaking, the main drawback of all these methods is the drop of efficiency for deep regions and obese patient. Delivering robust elastic waves in depth is an issue. We have proposed in the past a solution that avoid the problem of shear wave penetration using active sources. It consists in using natural shear waves that exist everywhere in living tissues. These natural shear wave are created thanks to heart beating, to pulse wave within arteries or to muscle activities. Since a few years now, we have been tracking natural shear waves in different soft tissues of the human body and we have not yet been disappointed. Using uncontrolled shear wave needs a change in the g...