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

Abstract

To investigate temperature changes around the fibres of the super pulse thulium fibre laser (SP-TFL) during in vitro lithotripsy. 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 irrigation 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. Without irrigation, the temperature around the fibre rapidly reached the safety threshold of 43℃ at 24 s. At 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℃. 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.