Ultrasound-based transient elastography using a magnetic excitation

Magneto-motive ultrasound is an imaging technique where magnetic particles, in tissues, are displaced by an external magnetic field and the resulting displacements are evaluated using ultrasonic echo signals. The magneto-motive ultrasound method has been, for example, used to detect movements of superparamagnetic nanoparticles. However, the viscoelastic properties of tissues greatly affect the ability of magneto-motive force to displace the particles and, consequently, its surrounding medium. Therefore, having knowledge about the elastic properties of the region where the magnetic particles are located is a useful parameter to improve the magneto-motive ultrasound images. Several quantitative methods to estimate the elastic properties of tissues using ultrasound have been developed. In the present study, we propose the magneto-motive ultrasound as a method to characterize the viscoelastic properties of tissues. We used a coil to induce movements to a viscoelastic phantom containing magnetic particles, and the transient response was evaluated cross-correlating ultrasonic echoes acquired during the magnetic excitation. The resulting seismic waves (compressional, shear and surface waves) were detected, and used to estimate the elastic properties of the phantom.