Designing an array for acoustic manipulation of kidney stones

Remote acoustic manipulation of objects in three dimensions has been achieved through acoustic radiation forces imparted by designed acoustic beam traps. This technology can be used as a noninvasive medical tool to control foreign objects in the body. Success of this technology requires the ability to transmit complex beam shapes through the tissue while maintaining stable and robust acoustic traps. Vortex beams and other acoustic beam traps were synthesized using a 1.5 MHz, focused, multi-element array to trap and manipulate glass spheres mimicking stones. Measurements of the radiation forces agreed with calculations to within <10%. The strength of the trapping stability and steering range of the acoustic traps were achieved by controlling the pulsing directionality to eliminate rotational instability, geometrical shape of the beam relative to target size, and acoustic power of the beam. Spheres were noninvasively moved along predefined paths in the urinary bladders of pigs without morphological injury. To further improve the technology of remote manipulating of kidney stones, simulations and experiments were used to define a design and parameters of a 256-element array to move 2–5mm stones distances up to 3 cm in a kidney. [Work supported by NIH P01-DK043881 and APL SEED Fellowship.]