Assessment of Holmium:YAG, Pulsed-Thulium:YAG and Thulium Fiber Lasers for Urinary Stone Ablation. In Vitro Study.

Objective

To evaluate the ablation speed (AS), laser efficiency and direct thermal lesions during urinary stone lithotripsy with the current available laser technologies: Holmium:YAG (Ho:YAG), pulsed-Thulium:YAG (p-Tm:YAG) and thulium fiber laser (TFL) in vitro using different laser settings. Materials and

Methods

Ho:YAG, p-Tm:YAG, and TFL laser system were used in an in vitro ureteral model with a volume of 125 mm3 Begostone. The following parameters were tested across all laser devices: 0.6J/10 Hz (6 W), 0.6 J/20 Hz (12 W), 1.5 J/10 Hz (15 W), and 1.5 J/20 Hz (30 W), employing short pulse width for all lasers and long pulse width for Ho:YAG and p-Tm:YAG. Ten participants conducted the experimental setup during 3-minutes laser on time, combining the laser technology, settings, and pulse widths, with a total of 20 different combinations. The efficiency, AS and ureteral damage resulting from each intervention were analyzed.

Results

p-Tm:YAG and TFL demonstrated significantly higher efficiency compared with Ho:YAG (0.049 ± 0.02 Δgr/KJ and 0.042 ± 0.01 Δgr/KJ vs 0.029 ± 0.01 Δgr/KJ; p < 0.05). In all laser sources, as the power increases, the AS also increases (p < 0.05). Furthermore, only at high-energy settings (1.5 J) higher frequency led to increase AS (p < 0.05). Both, p-Tm:YAG and TFL exhibited higher AS compared to Ho:YAG (0.64 ± 0.33 Δgr/s and 0.62 ± 0.31 Δgr/s vs 0.44 ± 0.22 Δgr/s; p < 0.05). Regarding ureteral injuries, as the power increases, there is a higher chance of ureteral damage (p = 0.031). No differences were observed between laser technologies (p = 0.828).

Conclusions

Both, p-Tm:YAG and TFL exhibited superior performances during laser lithotripsy compared with Ho:YAG, as they demonstrated higher efficiency and ablation speed. Thermal damage did not appear to be associated with specific laser equipment, but higher grades of lesions are described by increasing power.