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Mechanisms of Stone Fragmentation Produced by Nano Pulse Lithotripsy (NPL)

机译：纳米脉冲碎石术（NPL）产生碎石的机制

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摘要

Nano Pulse Lithotripter (NPL) is a new technology in intracorporeal lithotripsy. It utilizes a high-voltage spark discharge of about 30-nanosecond duration, released at the tip of a flexible probe under endoscopic guidance, to break up kidney stones into fine powders for spontaneous discharge. Several primary damage patterns have been observed during the NPL treatment of hard and soft BegoStones: crater formation near the probe tip, crack development from the distal wall of the stone, and crack initiation in the form of radial and ring-shape circumferential fracture in the proximal surface of stones of small sizes. Compared to the traditional intracorporeal lithotripsy technologies (laser and EHL), NPL has been shown to comminute kidney stones with higher efficiency, especially with hard stones, although its working mechanisms are largely unclear. Multiple potential contributory factors have been proposed: direct dielectric breakdown in the stone material near the NPL probe tip, shock wave induced by the spark discharge in the fluid, and cavitation and resultant asymmetric collapse of bubbles. Various experiments have been carried out to correlate each of the proposed mechanisms with the damage patterns observed. Comparison between micro-CT images of the damage initiation sites and COMSOL simulation of the stress field in the stone indicate that the observed cracks are most likely to be produced by the locally intensified tensile stresses associated with the surface acoustic waves (SAW) generated by the incidence of the spark-generated, spherically divergent shock wave on the proximal surface of the stone, and/or their interactions with bulk acoustic waves (P or S) upon reflection from the stone boundaries. Dielectric breakdown is found to potentially contribute to crater formation, especially for soft BegoStones. However, the contribution of cavitation to stone fragmentation in NPL appears to be minimal.
机译：纳米脉冲碎石机（NPL）是一种体内碎石术的新技术。它利用约30纳秒持续时间的高压火花放电，在内窥镜引导下在柔性探头的尖端释放，将肾结石分解成细粉，用于自发放电。在NPL处理硬和软BegoStones的过程中，已经观察到几种主要的损坏模式：在探针尖端附近形成火山口，从石头的远端壁产生裂纹，以及以径向和环形圆周断裂的形式产生裂纹。小尺寸结石近端表面。与传统的体内碎石术技术（激光和EHL）相比，NPL已被证明能以更高的效率粉碎肾结石，尤其是硬结石，尽管其工作机理尚不清楚。已经提出了多种潜在的促成因素：NPL探针尖端附近石材中的直接介电击穿，流体中火花放电引起的冲击波，气蚀和气泡的不对称塌陷。已经进行了各种实验，以使每个提出的机制与观察到的损伤模式相关。损伤起始位点的微CT图像与石头中应力场的COMSOL模拟结果之间的比较表明，观察到的裂纹最有可能是由与表面声波（SAW）相关的局部增强拉伸应力产生的。在石头近端表面上产生火花的球形发散冲击波的发生率，和/或它们在从石头边界反射时与体声波（P或S）的相互作用。已发现介电击穿可能会形成陨石坑，特别是对于柔软的BegoStones。但是，空化对不良贷款中石头碎裂的贡献似乎很小。

著录项

  • 作者

    Yang, Chen.;

  • 作者单位

    Duke University.;

  • 授予单位 Duke University.;
  • 学科 Mechanical engineering.;Acoustics.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 177 p.
  • 总页数 177
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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