Acoustic manipulation of large solid objects for medical applications

Abstract

Most progress in acoustic manipulation through radiation forces has been achieved in the trapping and levitation of small and low-density objects. We are developing traps to manipulate large dense objects. Such technology could be used to noninvasively steer a kidney stone along a complex path in the kidney fluid space to pass a small stone before it is symptomatic. In this work various acoustic beams were generated with a focused, 1.5-MHz, 256-element array and used to trap, levitate, and manipulate in three-dimensions (3-D) 3-5 mm glass spheres. The radiation forces from these beams were simulated and measured for different target and trap sizes. Good agreement between calculations and measurements of the forces was found, with an average discrepancy of 12 %. At 10-W acoustic power, the lateral trapping forces were 0.5–3 times the gravitational forces in water. 3-D stability and off-axis steering were achievable only when the ratio of beam diameter to the target diameter was ≳1. Glass spheres placed in the focus of the array were manipulated over a preprogrammed 3-D path at pressure and intensity levels safe for clinical exposure. [Work supported by NIH P01-DK043881, K01-DK104854, R01-EB007643, and RBBR 17-02-00261.]