An ultra-high-rate ultrasonic scanner has been developed that can give 5000 ultrasonic images per second of the body. With such a high frame rate, the propagation of transient shear waves can be followed, and from the spatio-temporal evolution of the displacement fields, various inversion algorithms allow us to recover the shear modulus map. A discussion on the various inversion algorithms will be presented. In order to obtain unbiased shear elasticity map, different configurations of shear sources induced by radiation pressure of focused transducer arrays are used. Both 2-D and 3-D imaging can obtained with this technique. In vitro and in vivo results on breast will be presented that demonstrate the interest of elasticity imaging with transient elastography.