Temperature variations with Ho: YAG and thulium fiber lasers, including advanced fragmentation pulse (AFP) technology: an experimental analysis

Abstract

Purpose: Recent developments in high-power systems and the super-pulsed thulium fiber laser (TFL) promise enhanced efficiency but raise concerns about thermal safety. This study examines the intrarenal temperature profiles of Ho: YAG and TFL systems including the advanced fragmentation pulse (AFP) mode under simulated conditions.

Methods: A custom-designed kidney and ureter model was used to measure intrarenal temperature changes during laser activation. Real-time temperature data were recorded via thermocouples placed in collecting system. Results were analyzed to compare water temperature increases with the safety threshold of 43 °C.

Results: At an irrigation flow rate of 23 mL/min and an initial water temperature of 22 ± 1 °C, WTIs for all laser systems remained below the safety threshold of temperature increase (STTI) during 60 s of laser activation. Ho: YAG consistently demonstrated the lowest WTIs, whereas TFL in AFP mode showed higher WTIs comparable to Ho: YAG but lower compared to TFL standard mode. Across all settings, WTIs were highest in the pelvis due to proximity to the laser fiber, with lower values in the upper and lower poles. The rapid temperature rise observed in the first 10-15 s was followed by a slower, steady increase. These findings confirm that with proper irrigation, even high-power laser lithotripsy systems, including TFL with AFP, operate within thermally safe limits.

Conclusion: This study confirms that both Ho: YAG and TFL systems, including AFP mode, remain thermally safe with adequate irrigation (23 mL/min) during 60-second activation sessions.

Keywords: Ho:YAG; Laser lithotripsy; Thermal injury; Thulium fiber laser.