Design of a phased-array for radiation force generation following a closed path

This work demonstrates with numerical simulations, the feasibility of an ultrasound probe for the generation of radiation forces in set of points following a path surrounding a tumor. Such strategy is adapted to induce resonance elastography of breast tumors and/or to increase displacement magnitudes induced by low frequency shear waves. Transducer elements were based on 1-3 piezocomposite material. 3D simulations combining the finite element method and boundary element method with periodic boundary conditions in the elevation direction were used to predict acoustic wave radiation in the breast. The crosstalk between neighbor elements was not taken into account. The coupling factor of the piezocomposite material and the radiated power of the transducer were optimized. The transducer electrical impedance was targeted to 50 Ω. The final probe was simulated by assembling the designed transducer to build an octagonal phased-array, with 256 elements on each edge. Using dynamic transmitter beamforming techniques, the electrical excitation that generates the radiation force along a path and resulting acoustic pattern in the breast were evaluated. Transducers central frequency was 4.5 MHz; they were able to deliver enough power and could generate the radiation force with a relatively low level of voltage excitation. Magnitude and orientation of the acoustic intensity (radiation force) at any point of a path were controlled.