Ultrafast imaging of transient shear waves for breast elastography: First clinical results

Abstract

Transient elastography of soft human tissues has been developed in our lab for several years. This technique consists in following the shear wave propagation induced by a low frequency pulsed vibrator located at the surface of the body with an ultrasonic imaging system. As the shear wave speed can reach up to 10 m/s, an ultrafast imaging system made of 128 fully programmable and independent channels has been developed able to produce 5000 images/s. Such frame rates are attainable by limiting the emission to a plane wave illumination and achieving the beamforming only in the receive mode. The comparison of successive images by classical cross-correlation techniques allows us to produce a 2-D movie of the displacements induced by the shear wave deep inside the body. An inversion algorithm is then used to recover the shear modulus map from the spatiotemporal data. We present here the first clinical results obtained on 20 female patients. These preliminary results of quantitative imaging of breast elasticity are very promising. The limits of the system due to shear wave diffraction are discussed and the improvements planned for the next clinical experiments are discussed.