Laser lithotripsy is the preferred application for the destruction of ureteral and kidney stones. Clinically Ho:YAG lasers (λ=2.1μm) are used due to high absorption by water to induce thermomechanical ablation. This study focussed on the investigation of different laser parameters in relation to the stone dusting efficiency. The term dusting was defined when the ablated fragments were d<1mm in diameter while fragmentation is defined to pieces of d> 1mm. The discussion about fragment-size showed advantages like reduced surgery time.
Experiments were performed using clinical available Ho:YAG laser energy transferred via a standard fibre (Ø: 365μm) onto phantom calculi (Bego-Stones of different hardness) in a water filled vessel.
Dusting can be reached most efficient by using low energy/pulse (approx. 0.5J/pulse) and repetition rate of around 40 Hz. Higher energy/pulse showed strong repulsion and thereby increased mobility, while using lower repetition rates result in longer ablation times. With regard to the hardness of the phantoms it can be derived that on soft calculi or calculi with a very rugged surface dusting can be observed less because the stone breaks into large fragments after a short time of laser application. For hard calculi the ablation process takes a much longer time compared to soft stones.
In the following will be shown that dusting and fragmentation process depends not only on the energy/pulse and repetition rate of a Ho:YAG-laser, but also there are differences between Ho:YAG-laser systems according to the dusting efficiency.
Max Eisel, Keerthanan Ulaganathan, Frank Strittmatter, Thomas Pongratz, and Ronald Sroka, "Investigations to improve laser induced lithrotripsy (Conference Presentation)," Proc. SPIE 10038, Therapeutics and Diagnostics in Urology: Lasers, Robotics, Minimally Invasive, and Advanced Biomedical Devices, 100380E (Presented at SPIE BiOS: January 28, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2254982.5369935431001.
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