Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina, USA.
Division of Urology, Department of Surgery, Duke University Medical Center, Durham, North Carolina, USA.
J Endourol. 2021 Jun;35(6):860-870. doi: 10.1089/end.2020.0349. Epub 2021 Mar 18.
Although cavitation during laser lithotripsy (LL) contributes to the Moses effect, the impact of cavitation on stone damage is less clear. Using different laser settings, we investigate the role of cavitation bubbles in energy delivery and stone damage. The role of cavitation in laser energy delivery was characterized by using photodetector measurements synced with high-speed imaging for laser pulses of varying durations. BegoStone samples were treated with the laser fiber oriented perpendicularly in contact with the stone in water or in air to assess the impact of cavitation on crater formation. Crater volume and geometry were quantified by using optical coherence tomography. Further, the role of cavitation in stone damage was elucidated by treatment in water with the fiber oriented parallel to the stone surface and by photoelastic imaging. Longer pulse durations resulted in higher energy delivery but smaller craters. Stones treated in water resulted in greater volume, wider yet shallower craters compared with those treated in air. Stones treated with the parallel fiber showed crater formation after 15 pulses, confirmed by high-speed imaging of the bubble collapse with the resultant stress field captured by photoelastic imaging. Despite improved energy delivery, the longer pulse mode produced smaller crater volume, suggesting additional processes secondary to photothermal ablation are involved in stone damage. Our critical observations of the difference in stone damage treated in water in air, combined with the crater formation by parallel fiber, suggest that cavitation is a contributor to stone damage during LL.
虽然激光碎石术 (LL) 过程中的空化作用有助于摩西效应，但空化作用对结石损伤的影响尚不清楚。我们使用不同的激光设置，研究了空化气泡在能量传递和结石损伤中的作用。通过使用与不同持续时间的激光脉冲同步的光电探测器测量和高速成像来表征空化对激光能量传递的作用。使用光学相干断层扫描对贝戈石样品进行处理，将激光光纤垂直于与水或空气中的结石接触的方向定位，以评估空化对坑形成的影响。通过光弹性成像，进一步阐明了空化在结石损伤中的作用，具体方法是将光纤平行于结石表面定位并在水中进行处理。较长的脉冲持续时间导致更高的能量传递，但坑更小。与在空气中处理相比，在水中处理的结石会产生更大的体积、更宽但更浅的坑。用平行光纤处理的结石在 15 次脉冲后出现坑形成，这通过气泡坍塌的高速成像得到证实，同时通过光弹性成像捕获的结果应力场。尽管能量传递得到了改善，但较长脉冲模式产生的坑体积较小，这表明在结石损伤中除光热烧蚀外，还有其他次要过程参与。我们对水和空气中处理的结石损伤差异的关键观察结果，结合平行光纤产生的坑形成结果，表明空化是 LL 过程中结石损伤的一个因素。
