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 calculus 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 information about time‐dependent acoustic energy propagation and its interaction with cavitation, 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.
Part of the book: Updates and Advances in Nephrolithiasis
Even though ureteroscopic laser lithotripsy (URSL) has become the preferred treatment option for urolithiasis due to shorter operation time and a better stone-free rate, the optimum laser pulse settings for URSL with the shortest operative times remain unknown. In this chapter, two sets of design of experiments (DOE) were conducted with response surface methodology: 1) the quantitative responses of calculus ablation and retropulsion in terms of the pulse energy, pulse width, and the number of pulses of a prototype Chromium (Cr3+), Thulium (Tm3+), Holmium (Ho3+) triple doped yttrium aluminum garnet (CTH:YAG) laser system. The ablation or retropulsion is inversely proportional to the pulse width, and the pulse width has a higher impact coefficient for the ablation than for the retropulsion. The quadratic fit of the response surface for the volume of ablation has a nonlinear relationship with the pulse width and number of pulses. 2) the laser setting optimization of laser lithotripsy of a commercially available CTH: YAG laser system. The experimental setup is based on a benchtop model first introduced by Sroka’s group. Comparing to frequency, the laser pulse energy or peak power has a higher impact coefficient to stone retropulsion as compared to stone ablation in CTH: YAG laser lithotripsy. The most efficient way to curtail stone retropulsion during laser lithotripsy is to lower the laser pulse peak power.
Part of the book: Response Surface Methodology in Engineering Science
The higher annual growth rate of kidney stone disease occurrence and the lower annual growth rate of practicing urologists require more efficient treatment tools. This chapter’s research explores ways to increase laser lithotripsy stone ablation efficiency while reducing the stone retropulsion so that the stone procedure time can be effectively shortened. It covers the investigation of laser stone ablation threshold, ablation efficiency, retropulsion control, and the optimal dusting mode of a concept Holmium-doped yttrium aluminum garnet (Ho:YAG) laser with advanced tailored pulse technology to produce a high ablation rate and low retropulsion. Ho:YAG laser stone damage and recoil movement were investigated in vitro utilizing a tabletop model in a highly reproducible manner while evaluating the effects of several laser mode pulses. A thorough evaluation of the pseudo-optimal dusting mode’s behavior (dusting rate and recoil movement) against a standard laser dusting mode was performed. The optimal dusting mode in this benchtop test model maintained a modest level of retropulsion while having a somewhat quick ablation rate. The transient pressure field measurement results of the standard and custom laser modes of a concept Ho: YAG laser are also included.
Part of the book: Lithotripsy