Comparative Analysis of Steady-State and Burst Lasing in Thulium Fiber Laser Lithotripsy
Overview
This study compares steady-state (continuous) and burst lasing modes of thulium fiber laser (TFL) lithotripsy using an in vitro ureteral model. It evaluates stone ablation efficacy and ureteral thermal injury, highlighting the balance between effective stone fragmentation and safety concerns related to laser settings and activation patterns.
Background
Thulium fiber lasers have gained attention as a promising alternative to holmium:YAG lasers for urological lithotripsy due to potential improvements in safety and efficacy. However, concerns about thermal injury and ureteral strictures have emerged, especially with high-power settings and continuous lasing. Burst lasing, involving intermittent laser activation, has been proposed to mitigate thermal damage by allowing cooling periods, but its safety and efficacy compared to steady-state lasing remain under investigation. This study uses a controlled in vitro model to systematically compare these two lasing methods.
Data Highlights
Parameter
Steady-State Lasing (C)
Burst Lasing (B)
Laser On Time (LOT)
Continuous until 1.5 kJ delivered
Intermittent 5 s on / 5 s off cycles until 1.5 kJ delivered
Laser Active Time
100%
50%
Stone Ablation Measurement
Weight difference pre/post lithotripsy
Weight difference pre/post lithotripsy
Ureteral Damage Scoring
1 (no lesion) to 3 (burns)
1 (no lesion) to 3 (burns)
Key Findings
Steady-state lasing delivers continuous laser energy, resulting in consistent stone ablation but with potential for increased thermal injury.
Burst lasing uses a 5-second on/off cycle, reducing laser active time to 50%, which may help mitigate thermal damage by allowing cooling intervals.
Stone ablation efficacy was assessed by percentage weight reduction of BegoStone™ phantoms after treatment with both lasing modes.
Ureteral model damage was classified on a 3-point scale, with burst lasing hypothesized to reduce thermal lesions compared to steady-state lasing.
Participants included both trainees and experienced urologists, ensuring assessment across different operator skill levels.
Maintaining adequate irrigation (gravity plus hand-assisted) was critical to controlling thermal effects during both lasing modes.
Clinical Implications
Clinicians should consider burst lasing as a strategy to reduce thermal injury risk during TFL lithotripsy by incorporating intermittent laser activation and adequate irrigation. While steady-state lasing may offer continuous stone fragmentation, it carries a higher risk of thermal damage, especially at high power settings. Careful selection of laser mode and power settings, along with operator training, is essential to optimize safety and efficacy.
Conclusion
This comparative in vitro study highlights that burst lasing may provide a safer alternative to steady-state lasing by reducing thermal injury without compromising stone ablation efficacy. Further clinical studies are warranted to confirm these findings and guide optimal TFL lithotripsy protocols.
References
Recent studies on TFL vs Ho:YAG lasers (2020-2023) -- Safety and efficacy in lithotripsy
FDA Class 2 Device Recall (Olympus, 2023) -- Thermal injury concerns with TFL
In vitro ureteral model and BegoStone phantom methodology (2021-2023)
