**Investigation of Laser Pulse‐induced Calculus Damage Mechanism by a High‐speed Camera**

Jian J. Zhang, Rongwei J. Xuan and Thomas Hasenberg

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http://dx.doi.org/10.5772/intechopen.69981

#### **Abstract**

Even though laser lithotripsy has become the most popular treatment choice for kidney stone disease, the mechanism calculus disintegration by laser pulse remains unclear. This is due to the multiple physical/chemical processes involved in laser pulse‐caused calcu‐ lus damage and their sub‐microsecond timescales. A high‐speed camera with a frame rate up to 1 million frames per second (fps) was employed in this study. The results revealed the cavitation bubble dynamics (oscillation and center of bubble movement) by Ho‐ and Tm‐laser pulses at a different energy level and pulse width. Besides, fiber‐tip degradation, damage, or burn‐back is a common problem during the ureteroscopic laser lithotripsy procedure to treat urolithiasis. The results suggested that using a high‐speed camera and the Schlieren method to visualize the shock wave provided valuable infor‐ mation about time‐dependent acoustic energy propagation and its interaction with cavi‐ tation, the fiber tip, and calculus. And lastly, calculus migration is a common problem during ureteroscopic laser lithotripsy procedure to treat urolithiasis. In this investigation, calculus retropulsion was studied using a suspended pendulum in water to get rid of the friction. The results suggested that using the pendulum model to eliminate the friction improved sensitivity and repeatability of the experiment.

**Keywords:** calculus, cavitation, bubble, dynamics, shock wave, oscillation, high‐speed camera, fiber burn‐back, retropulsion, laser lithotripsy

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