In Vitro Ablation Rates of Ho:YAG, p-Tm:YAG and TFL Lasers

Abstract Objective This study compares the ablation rates of three laser systems—Holmium:YAG (Ho:YAG), Thulium Fiber Laser (TFL), and Pulsed Thulium:YAG (p-Tm:YAG)—for renal stone lithotripsy using a standardized robotic setup. Materials and Methods A robotic arm enabled consistent laser application on stone phantoms simulating calcium oxalate monohydrate (hard) and uric acid (soft) stones. Ablation efficiency (mm³/J) was assessed across different laser settings (0.2 J – 50 Hz, 0.5 J – 20 Hz, and 1.0 J – 10 Hz) and fiber diameters (200 and 272 µm). Ablated volumes were quantified via micro-CT and 3D segmentation using 3DSlicer. Statistical analysis evaluated differences in performance. Results TFL demonstrated the highest ablation rates for both hard and soft stones, significantly outperforming Ho:YAG in multiple settings. For hard stones, TFL exhibited greater ablation efficiency than Ho:YAG, particularly at 0.5 J − 20 Hz and 1.0 J − 10 Hz. The p-Tm:YAG laser also outperformed Ho:YAG at 0.5 J − 20 Hz. For soft stones, the difference between TFL and Tm:YAG was statistically significant at lower energy settings (0.20 J − 50 Hz and 0.5 J − 20 Hz). Compared to Ho:YAG, TFL showed significantly higher ablation rates across all tested settings (p < 0.05). The p-Tm:YAG laser showed intermediate performance, with higher efficiency than Ho:YAG but slightly lower than TFL. Fiber diameter influenced ablation, with 272 µm fibers yielding greater efficiency at lower energy settings (p < 0.05 at 0.20 J − 50 Hz and 0.5 J − 20 Hz for both stone types); this comparison was limited to p-Tm:YAG, as data for the other lasers are already available in the literature. Conclusion TFL achieved the highest in vitro ablation efficiency. However, p-Tm:YAG represents a promising compromise, offering improved performance over Ho:YAG and a balanced profile between fragmentation and dusting capabilities.