Study of Temperature Changes Around Fibres in Super Pulse Thulium Fibre Laser in Vitro Lithotripsy

Purpose: To investigate temperature changes around the fibres of the super pulse thulium fibre laser (SP-TFL) during in vitro lithotripsy. Materials and Methods: Stones were placed in the in vitro model. The laser was continuously excited for 180 s; the probe was positioned 5 mm around the fibre; the laser power was set at 10, 15, 20, 25, and 30 W; and the irri-gation rate was set at 0, 15, 25, 35 ml/min, using a domestic SP-TFL. The temperature variations around the fibre under different power settings and different irrigation rates were compared. Results: Without irrigation, the temperature around the fibre rapidly reached the safety threshold of 43? at 24 s. At an irrigation rate 15 ml/min and laser power <15 W, the temperature around the fibre was < 43?. Once the laser power increased to > 20 W, the temperature around the fibre increased to >43? at its lowest plateau. At irrigation rate 25 ml/min and laser power < 25 W, the temperature around the fibre was < 43?. At irrigation rate 35 ml/min and laser power < 30 W, the fibre temperature was < 43?. When laser power was > 30 W, the fibre temperature was > 43?.Conclusion: In extracorporeal ureteroscope SP-TFL lithotripsy, when the laser power is < 15 W, < 25 W, and < 30 W, the irrigation rate should be maintained at > 15 ml/min, > 25 ml/min, and > 35 ml/min, respectively.