Shear Wave Generation by Remotely Stimulating Aluminum Patches With a Transient Magnetic Field and Its Preliminary Application in Elastography

Objective: This article presents shear wave generation by remotely stimulating aluminum patches through a transient magnetic field, and its preliminary application in the cross-correlation approach based ultrasound elastography. Methods: A transient magnetic field is employed to remotely vibrate the patch actuators through the Lorentz force. The origin, and the characteristics of the Lorentz force are confirmed using an interferometric laser probe. The shear wave displacement fields generated in the soft medium are studied through the ultrafast ultrasound imaging. The potential of the shear wave fields generated through the patch actuators for the cross-correlation approach based elastography is confirmed through experiments on an agar phantom sample. Results: Under a transient magnetic field of changing rate of 10.44 kT/s, the patch actuator generates a shear wave source of amplitude of 100 μm in a polyvinyl alcohol (PVA) phantom sample. The shear wave fields created by experiments agree qualitatively well with those by theory. From the shear wave velocity map computed from 100 frames of shear wave fields, the boundaries of cylindrical regions of different stiffness can be clearly recognized, which are completely concealed in the ultrasound image. Conclusion: Shear wave fields in the level of 100 μm can be remotely generated in soft medium through stimulating aluminum patches with a transient magnetic field, and qualitative shear wave velocity maps can be reconstructed from the shear wave fields generated. Significance: The proposed method allows potential application of the cross-correlation approach based elastography in intravascular-based or catheter-based cardiology.