A multi-element HIFU array system: Characterization and testing for manipulation of kidney stones

Abstract

Most progress in acoustic trapping and levitation has been achieved with the use of multiple sound sources, standing waves, and low density or very small objects. Repositioning kidney stones in the human body is an important clinical application where acoustic levitation could be employed; however, it requires manipulation of larger and heavier objects. The goal of this work was to calibrate the acoustic output of a 1.5-MHz, 256-element array designed in our laboratory for HIFU research, which is also capable of generating vortex beams to manipulate mm-sized objects in water and to move them in any direction without moving the source. Electrical circuits were developed for matching each element of the array to an output channel of a Verasonics ultrasound engine to allow for efficient power transfer to the transducer. Acoustic holography was used to calibrate and equalize outputs across all channels. Manipulation of artificial kidney stone targets made of plastic, glass, or cement (2—8 mm) and comparable in size to or larger than the wavelength in water by electronic steering of the vortex beam lateral to the acoustic axis was demonstrated. [Work supported by NIH P01 DK043881, K01 DK104854, R01 EB007643, and NSBRI through NASA NCC 9-58.]