FIG. 7.

(Color online) Artificial plaster stones that mimic human stones were fragmented with the broadly focused transducer (focal width ∼11 mm) and conventional spherically focused transducer (focal width in lateral plane = 6 mm). The cylindrical stones had a diameter of 6 mm and length of 11 mm with avg. weight = 0.690 ± 0.011 g. They were fragmented for half an hour, and the mass of fragments smaller than 2 mm was measured every 10 min. The transducers were operated at 350 kHz with a pulse repetition frequency of 20 and at the same negative pressure amplitude (–5.7 MPa). The broadly focused transducer fragmented 44 ± 9% of stone by weight in 30 min, whereas the focused transducer fragmented only 16 ± 4% of the stone in the same duration.