Holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripsy (LL) has been the treatment of choice for kidney stone disease for more than two decades, yet the mechanisms of action are not completely clear. Besides photothermal ablation, recent evidence suggests that cavitation bubble collapse is pivotal in kidney stone dusting when the Ho:YAG laser operates at low pulse energy (Ep) and high frequency (F). In this work, we perform a comprehensive series of experiments and model-based simulations to dissect the complex physical processes in LL. Under clinically relevant dusting settings (Ep = 0.2 J, F = 20 Hz), our results suggest that majority of the irradiated laser energy (>90 %) is dissipated by heat generation in the fluid surrounding the fiber tip and the irradiated stone surface, while only about 1 % may be consumed for photothermal ablation, and less than 0.7 % is converted into the potential energy at the maximum bubble expansion. We reveal that photothermal ablation is confined locally to the laser irradiation spot, whereas cavitation erosion is most pronounced at a fiber tip-stone surface distance about 0.5 mm where multi foci ring-like damage outside the thermal ablation zone is observed. The cavitation erosion is caused by the progressively intensified collapse of jet-induced toroidal bubble near the stone surface (<100 μm), as a result of Raleigh-Taylor and Richtmyer-Meshkov instabilities. The ensuing shock wave-stone interaction and resultant leaky Rayleigh waves on the stone surface may lead to dynamic fatigue and superficial material removal under repeated bombardments of toroidal bubble collapses during dusting procedures in LL.
Ultrasonics sonochemistry. 2023 Oct 15 [Epub ahead of print]
Gaoming Xiang, Junqin Chen, Derek Ho, Georgy Sankin, Xuning Zhao, Yangyuanchen Liu, Kevin Wang, John Dolbow, Junjie Yao, Pei Zhong
Thomas Lord Dept. of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708, USA; Current address: Optics and Thermal Radiation Research Center, Institute of Frontier and Interdisciplinary Science, Shandong University, Qingdao 266237, China., Thomas Lord Dept. of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708, USA., Dept. of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA., Dept. of Biomedical Engineering, Duke University, Durham, NC 27708, USA., Thomas Lord Dept. of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708, USA. Electronic address: .