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.
Ultrason Sonochem. 2023 Dec;101:106649. doi: 10.1016/j.ultsonch.2023.106649. Epub 2023 Oct 15.
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 (E) 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 (E = 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.
钇铝石榴石（Ho:YAG）激光碎石术（LL）作为治疗肾结石的首选方法已经有二十多年了，但作用机制尚不完全清楚。除光热消融外，最近的证据表明，当 Ho:YAG 激光以低脉冲能量（E）和高频率（F）运行时，空化气泡的坍塌在肾结石粉化中起着关键作用。在这项工作中，我们进行了一系列全面的实验和基于模型的模拟，以剖析 LL 中的复杂物理过程。在临床相关的粉化设置下（E=0.2 J，F=20 Hz），我们的结果表明，大部分辐照激光能量（>90%）通过在光纤尖端周围的流体和辐照结石表面耗散产生的热来耗散，而只有约 1%可能用于光热消融，不到 0.7%转换为最大气泡膨胀时的势能。我们揭示了光热消融局限于激光照射点，而空化侵蚀在光纤尖端-结石表面距离约 0.5 mm 处最为明显，在热消融区外观察到多焦点环状损伤。空化侵蚀是由近结石表面（<100 μm）的射流诱导的环形气泡逐渐增强的坍塌引起的，这是由于 Raleigh-Taylor 和 Richtmyer-Meshkov 不稳定性造成的。随后的冲击波-结石相互作用以及结石表面上的漏射瑞利波可能导致在 LL 粉化过程中，在环形气泡反复坍塌的反复轰击下，结石表面出现动态疲劳和浅层材料去除。
