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 destruction efficiency. 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 an aquarium set-up. 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. For hard calculi the ablation process takes a much longer time compared to soft stones.
In addition the fluorescence of human urinary stones was investigated in-vitro as well as in-vivo. In-vitro investigations (n=30) were performed using fluorescence spectrometer and fluorescence microscopy techniques. Urinary stones show broad band fluorescence emission. Inhomogeneous local fluorescence sites and homogeneous surface fluorescence can be distinguished. The shell-like structure of the stones showed difference fluorescence behavior. The impact of fluorescence guidance during endoscopic laser lithotripsy will be discussed.
Ronald Sroka, Thomas Pongratz, Frank Strittmatter, Maximilian Eisel, and Stephan Ströbl, "In-vitro investigation on fragmentation/dusting and fluorescence during Ho:YAG-Laser induced lithotripsy (Conference Presentation)," Proc. SPIE 10468, Therapeutics and Diagnostics in Urology 2018, 1046807 (Presented at SPIE BiOS: January 27, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2291892.5751328145001.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon