Collateral damage to the ureter and Nitinol stone baskets during thulium fiber laser lithotripsy

BackgroundThe experimental Thulium fiber laser (TFL) is currently being studied as a potential alternative lithotripter to the clinical gold standard Holmium:YAG laser. Safety studies characterizing undesirable Holmium:YAG laser-induced damage to ureter tissue and stone baskets have been previously reported. Similarly, this study characterizes TFL induced ureter and stone basket damage. MethodsA TFL beam with energy of 35mJ per pulse, pulse duration of 500 mu s, and variable pulse rates of 50-500Hz, was delivered through 100-mu m-core optical fibers, to either porcine ureter wall, in vitro, or a standard 1.9-Fr Nitinol stone basket wire. Ureter perforation times were measured and gross, histological, and optical coherence tomography images of the ablation area were acquired. Stone basket damage was graded as a function of pulse rate, number of pulses, and working distance. ResultsTFL operation at 150, 300, and 500Hz produced mean ureter perforation times of 7.9, 3.8, and 1.8seconds, respectively. Collateral damage widths averaged 510, 370, and 310 mu m. Nitinol wire damage decreased with working distance and was non-existent at distances greater than 1.0mm. In contact mode, 500 pulses delivered at pulse rates 300Hz (1.5seconds) were sufficient to cut Nitinol wires. ConclusionsThe TFL, operated in low pulse energy and high pulse rate mode, may provide a greater safety margin than the standard Holmium:YAG laser for lithotripsy, as evidenced by longer TFL ureter perforation times and shorter non-contact working distances for stone basket damage than previously reported with Holmium:YAG laser. Lasers Surg. Med. 47:403-410, 2015. Lasers Surg. Med. 47:???-???, 2015. (c) 2015 Wiley Periodicals, Inc.