Generation of modulators for super-resolution imaging

Medical ultrasound imaging has a trade-off between the lateral image resolution and penetration depth. Using the Point Spread Function (PSF) modulation super-resolution imaging method developed recently (Lu, IEEE TUFFC 2024), it is possible to overcome such a limit. To implement the method, an ultrasound array transducer such as a one-dimensional (1-D), two-dimensional (2-D), or annular array transducer can be used to produce a shear wave deep in the biological soft tissues. The shear wave is then focused to form a modulator of a size of about one half of the shear wave wavelength. Notice that since the speed of sound of the shear wave is much smaller than that of the longitudinal waves, the shear wave wavelength can be small. Finally, the modulator is used to induce a phase modulation to the imaging wave for super-resolution ultrasound imaging. In this work, the mechanism of shear wave focusing is studied both theoretically and through computer simulations. The results show that it is possible to focus a shear wave to achieve a wave feature of about a half wavelength of the shear wave, opening up a possibility for super-resolution ultrasound imaging deep in the biological soft tissues.