Superpulse thulium fiber laser lithotripsy: an in vitro comparison of 200 μm and 150 μm laser fibers

Purpose To investigate the thermal effects, stone retropulsion and ablation rate of SuperPulse Thulium-fiber laser (SP TFL) with two different surgical fibers of 200 and 150 mu m in diameter. Methods SP TFL (NTO IRE-Polus, Fryazino, Russia) performance with 200 and 150 mu m fibers (NTO IRE-Polus, Fryazino, Russia) was evaluated. Before each test, the laser fiber was cleaved, and the power measurement was taken to verify the actual laser output power. To compare the laser fibers in well-controlled environments, a number of setups were used to assess retropulsion, ablation efficacy, fiber burnback, energy transmission, and safety. Results Power measurements performed before each test revealed a 4.7% power drop for a 200 mu m fiber SP TFL (14.3 +/- 0.5 W) and 7.3% power drop for a 150 mu m fiber SP TFL (13.9 +/- 0.5 W) versus the nominally indicated power (15.0 W). Retropulsion with the TFL was minimal and comparable between fibers. We found no clinically relevant temperature differences between SP TFL with either 200 or 150 mu m fibers. The ablation efficacy tended to be comparable under most parameters. Yet, we did observe a decreased diameter of residual fragments after the ablation with a 150 mu m fiber. Conclusion The smaller fiber (150 mu m) is not inferior to 200 mu m fiber in terms of fiber burnback, retropulsion, safety, and ablation rate. Moreover, it has the potential to decrease the diameter of fragments during lithotripsy, which may facilitate dusting during RIRS.