Combined radiation pressure field in a dual-frequency ultrasound system

The radiation force incident on an object in an ultrasound field has been utilized to create local displacements for making elastographic measurements. This study looks at the combined pressure field from two ultrasound transducers in a dual-frequency system to determine the radiation pressure field incident on an object in the focal plane. The combined pressure fields from a concentric-element transducer and a separate-element system with intersecting foci are analyzed. First, the combined pressure fields are calculated using a computer simulation of the summed linear fields. Then, the simulation results are shown to be in close agreement with experimental measurement of the pressure fields. Finally, the simulations are expanded to compute the radiation pressures for various target sizes and transducer geometries. A more thorough understanding of the resulting time-varying radiation pressure fields, as presented in this paper, facilitates the optimization of the dual-frequency set-up for radiation force imaging by providing general design guidelines for a dual-frequency imaging system.