Recent Advances in the Science of Burst Wave Lithotripsy and Ultrasonic Propulsion
Photoelastic image of stress waves created in a model stone by BWL. Photoelastic imaging reveals the stress (black) of the guided waves in the mm acrylic bar. The arrow shows the direction of ultrasound propagation (350 kHz). In this larger stone, the multiple-cycle structure of the BWL pulse causes guided waves to develop which cyclically concentrates and amplifies the stress  (courtesy of Adam Maxwell, University of Washington).