Plot of twinkle power versus time before, during, and after a pre-focal, off axis lithotripter pulse arrives at a cylindrical, artificial BegoStone. Overlaid on the plot are selected ROI Doppler images (image scale: 1-cm width) showing the stone (grey) and twinkling in color (if present). Twinkling is virtually nonexistent until the lithotripter pulse arrived at about 52 sec. When the pulse arrives, bubbles are excited on the BegoStone surface as observed with high-magnification, high-speed photography (right), and twinkling increases significantly for the duration of the pulse plus time for bubble oscillations. After the lithotripter pulse, twinkling returned to initial levels of little to no twinkling. These data were collected with the P4-2 transducer.