Sector-vortex scanning for hyperthermia with a large square ultrasound phased array aperture

Planar ultrasound (US) phased arrays with square element are easier to fabricate and model than other concave shaped phased arrays. Combined with phases derived for single spot focusing, the sector-vortex phase scheme can be applied to the square planar array to generate a vortex shaped pressure field that can be controlled by the mode number M. Increasing the mode number M also increases the diameter of the annular focus. The location of the annular focus can be moved along the axis or off axis by steering the single spot focus. The weight of the phase for single spot focusing can control the axial length of the sector-vortex pattern. Superposing the SAR of multiple modes can heat large tumors with diameters up to 5 cm by broadening the temperature distribution.