Introduction: High-power holmium lasers are becoming increasingly popular for ureteroscopic laser lithotripsy and dusting technique. Because settings and power selection may impact fiber-tip degradation and lithotripsy efficiency, we investigated the effect of pulse duration and pulse energy on fiber-tip degradation when using high-power settings for popcorn laser lithotripsy.
Methods: BegoStones were fragmented in an 11 mm bulb to simulate renal calyx, using a 120W Ho:YAG laser (Lumenis, CA). A 242 µm fiber (Boston Scientific, MA) was introduced through a ureteroscope mounted to a 3D positioner with its tip positioned at 2 mm distance from the stones (popcorn model). To assess the effect of pulse duration on tip degradation, settings with variable power of 1.0Jx20Hz (20W), 0.5Jx70Hz (35W), and 1.0Jx40Hz (40W) were tested on long pulse (LP) and short pulse (SP) modes. To assess the effect of pulse energy on tip degradation, high-power settings with equal power of 40W were tested (0.5Jx80Hz, 0.8Jx50Hz, and 1.0Jx40Hz) using SP. Experiments were conducted for a total duration of 4 minutes and outcome was fiber-tip length measured before and after each experiment using a digital caliper. Pulse duration and peak power were measured using a photodetector (DTE05D2, Thorlabs, NJ).
Results: Fiber-tip degradation was greatest when using SP compared to LP for all settings tested (P<0.01), with the highest degradation occurring at 1.0Jx40Hz using SP (Figure 1A). For 40W settings tested, tip degradation was significantly lower when using a pulse energy of 0.5J compared to 0.8J or 1.0J (P < 0.004; Figure 1B). Pulse energy of 0.5J at SP and LP had low peak power of 2.4 and 2.0 kW, respectively (Table 1).
Conclusions: Using LP mode results in less fiber burnback for all power settings tested. High-power 40W settings can be utilized with minimal fiber burnback if low pulse energy settings are used. Understanding these parameters can help clinicians improve the longevity of the laser fiber and improve procedural efficiency. Source of