LAUSR

Objective: To evaluate using an inanimate model the thermal injury and laser efficiency on high frequency, high energy and its combination in hands of junior and experienced urologists during holmium YAG (Ho:YAG) and Thulium fiber laser (TFL) lithotripsy. Methods: Cyber: Ho 150 WTM and Fiber Dust TFL (Quanta System) with 200µm core-diameter laser fibers (LF) were used in a saline in vitro ureteral model. Each participant (5 junior -5 experienced urologist) performed 32 sessions of 5 minutes lasering (125 mm3 phantom BegoStonesTM), comparing four modes (3J/5Hz (1.5W), 0.3J/20Hz (6W), 1.2 J/5Hz (6W), and 1.2J/20Hz (24W)). Transparent tip and cleaved LF, and digital and fiberoptic ureteroscopes were also compared. Ureteral damage was classified in a scale (0-5) according to the burns and holes seen in the ureteral model's surface. Results: High-power setting (24W) was associated with higher delivered energy and higher ablation rates in both lasers (p<0.001). For the same power setting (6W), there were no differences in delivered energy nor stone ablation rates. Regardless the settings, higher ablation rate was observed with TFL than with Ho:YAG ((0.5Δmg/s ± 0.33 vs 0.39 Δmg/s ± 0.31, p:0.002) laser. Higher mean ablation rate was found with cleaved tip vs transparent tip (p:0.03) in TFL. For both lasers, higher ureteral damage was observed in the 24W group (p: 0.006) and in the junior urologists (p: 0.03). Between 6W groups, different type of lesions were found and junior urologist have more lesions when high frequency was used, for both Ho:YAG (p=0.05) and TFL (p=0.04). Conclusion: High-power settings have more stone ablation rate and may reduce the operative time; however, more ureteral thermic-related damage is produced. When comparing the same power, higher energy or frequency does not modify the ablation rate. Nonetheless, more ureteral thermic-related thermal damage is observed in high frequency settings in unexperienced hands.