Various approaches for designing phased arrays for high-intensity focused ultrasound therapies: From sparse to fully-populated configurations

High-intensity focused ultrasound (HIFU) therapies are often performed using multi-element phased arrays. Independent variation of the amplitudes and phases at the array elements allows electronic steering of the focus and compensation for aberrations. To suppress the formation of grating lobes, the arrangement of the array elements should be non-periodic. Three approaches that have been recently employed in our studies to solve this problem are presented and discussed: a random element arrangement [L.R. Gavrilov and J.W. Hand, IEEE Trans. UFFC 2000], a multi-armed spiral arrangement [V.A. Khokhlova et al., Physics Procedia 2016], and recently proposed array design with tight packing of the elements based on the capacity-constrained tessellation [P.B. Rosnitskiy et al., IEEE UFFC 2018]. The efficiency of two arrays with the same geometric and physical parameters is compared: a 256-element array with a compact 16-spirals layout of circular elements and a fully populated array comprising polygonal elements of equal area. It is shown that for the same intensity at the elements, the fully-populated array provides twofold higher total power while maintaining the same electronic focusing capabilities as compared to the spiral one which can be beneficial for high-power applications such as histotripsy. [The work was supported by NIH R01EB7643 and R01EB025187, RFBR 17-02-00261, and Ph.D. student stipends from the “Basis” Foundation and of the President of Russia SP-2644.2018.4.]