V03-01: Understanding non-contact laser lithotripsy for dusting – the popcorn effect: A video analysis
The mechanism of stone breakdown and factors affecting fragmentation during non-contact holmium laser lithotripsy (the popcorn effect) at ureteroscopy (URS) are not fully understood. Using an in vitro model, we undertook high speed video analysis to better understand this mechanism and determine the effects of laser settings, calyceal size, flow rate, time, and heat generation on sub-millimeter fragmentation (i.e. dusting).
BegoStones (15:3) of fixed size were pulverized in a test tube calyceal model of various sizes (11, 15, and 19 mm) using a 120 W holmium laser (P120, Lumenis). A 200 μm laser fiber (Flexiva 200, Boston Scientific) was introduced through the working channel of a URS (LithoVue, Boston Scientific) connected to a 3D positioning system. The fiber was placed 1-2 mm away from the stones. Irrigation was provided at a height of 100 cm. Four different settings were assessed (1.0J x 20-40Hz, 0.5J x 40-80Hz). Video analysis was undertaken using a Photron high speed camera (10,000 and 500 frames per second). Experiments to determine optimal laser setting were conducted for 4 minutes (with 30 second intervals) and subsequent experiments were done at 3 minutes utilizing the best setting - assessing impact of calyceal size, flow rate and time. Fragments were sieved and the primary outcome was % fragments