结石表面曲率对HIFU碎石过程影响的实验分析

发布时间：2018-04-09 08:11

本文选题：高强度聚焦超声　切入点：超声空化碎石　出处：《清华大学》2014年硕士论文

【摘要】：肾结石病是一种常见病，在我国发病规模逐年增大。目前肾结石病的治疗方式如外科手术、体外冲击波碎石术等都存在副作用大、治疗效果差等弊端。随着超声空化现象的深入研究，越来越多的研究者开始致力于将超声空化运用于肾结石病的体外治疗。高强度聚焦超声(HIFU-High Intensity Focused Ultrasound)在液体中可以诱发强烈的空化现象，这种空化现象以空化云的形式出现。当这些空化云作用于肾结石时，空化泡破碎产生的高温高压以及微射流将会快速磨蚀肾结石，粉末可达微米级大小，足以快速排出体外。考虑到结石的不规则形状，本文通过改变由结石作用面曲率定义的参数ξ（ξ越大曲率越小；ξ=1时，结石作用面为平面）研究不同形状结石的碎石过程，，并通过高速摄影和声致发光的方法观察和测量空化云的行为。具体来说，本文建立了一套完整的超声空化碎石试验台，使用高强度聚焦超声换能器以及其配套设施产生聚焦空化场，制作不同曲率仿天然结石进行碎石试验，并通过3D扫描研究其体积损失随时间的变化。在除气NaCl溶液中，利用高强度脉冲激光诱发空化核定位空化云位置，使用高速摄像机记录空化云在聚焦超声场中的运动。在配置的鲁米诺溶液中，利用单反相机和光电倍增管观察、测量空化云造成的声致发光分布。主要研究结论如下：（1）超声空化碎石过程分两个阶段，第一阶段结石磨蚀由边缘开始，随后向中心靠拢。结石截面积逐渐增加，当达到空化云作用面面积（超声声场焦域截面积）时，外缘将不会被磨蚀进入第二阶段。在碎石开始阶段（0-30s），曲率更大（ξ更小）的结石模型获得了更快的碎石速度，随着曲率增加（ξ减少），体积损失越来越大，但在0.5后，体积损失的变化不再明显。（2）超声波在障碍物处反弹形成驻波，使空化云的上升过程出现脉动现象，在接触曲率壁面后，由于声流和壁面顶端的分流作用，空化云的振动区域在顶端附近形成环形区域。障碍物曲率的变化将会对空化云上升的速度有所影响，曲率更大（ξ更小）的壁面对应的空化云上升速度更快，反之则速度更慢。（3）加入结石模型后整体空化强度提高，结石周围形成回流，导致结石模型下方出现阻滞区域。这种情况随着ξ的逐步增大（曲率减小）越来越明显。结石模型的处于焦域中心偏上位置空化强度最高。
[Abstract]:Kidney stone disease is a common disease, in our country the scale of disease increases year by year.At present, the treatment of renal calculi, such as surgery, extracorporeal shock wave lithotripsy, has many disadvantages.With the in-depth study of ultrasound cavitation, more and more researchers begin to apply ultrasound cavitation to the treatment of renal calculi in vitro.HIFU-High Intensity Focused ultrasound (HIFU-High Intensity Focused ultrasound) can induce strong cavitation in liquid, which appears in the form of cavitation cloud.When these clouds act on the kidney stones, the high temperature and high pressure produced by the cavitation bubble breakup and the micro-jet will erode the kidney stone rapidly, and the powder can be as large as micron size, which is enough to be discharged from the body quickly.Considering the irregular shape of stone, this paper studies the lithotriptic process of stone with different shapes by changing the parameter 尉 defined by curvature of the action surface of stone, which is defined by curvature of stone action surface, which is smaller and bigger curvature; 尉 = 1, stone action surface is plane.The behavior of cavitation cloud was observed and measured by high-speed photography and sonoluminescence.Specifically, a complete set of ultrasonic cavitation gravel test bench is established, which uses high intensity focused ultrasonic transducer and its supporting facilities to produce focused cavitation field, and makes lithotripsy test with different curvature imitating natural stones.The change of volume loss with time was studied by 3D scanning.High intensity pulsed laser induced cavitation nuclei were used to locate the position of cavitation cloud in NaCl solution, and high-speed cameras were used to record the motion of cavitation cloud in focused ultrasound field.The sonoluminescence distribution caused by cavitation cloud was measured by using a SLR camera and a photomultiplier tube in the collocated Lumino solution.The main findings are as follows:Ultrasonic cavitation lithotripsy process is divided into two stages, the first stage of stone erosion from the edge, and then close to the center.The cross section area of stone increases gradually, and when the area of cavitation cloud action surface (focal area of ultrasonic sound field) is reached, the external edge will not be eroded into the second stage.In the initial stage of lithotripsy, the stone model with larger curvature (尉 smaller) obtains faster gravel velocity. With the increase of curvature (尉 decreases), the volume loss becomes larger and larger, but after 0.5, the change of volume loss is not obvious.2) the ultrasonic wave bounces back at the obstacle to form standing wave, which makes the rising process of cavitation cloud appear pulsating phenomenon. After contacting the curvature wall, the vibration region of the cavitation cloud forms a ring area near the top because of the flow of sound and the shunt of the top of the wall.The change of obstacle curvature will affect the rising speed of cavitation cloud, and the cavitation cloud with larger curvature (尉 smaller) will rise faster, otherwise it will be slower.3) after the stone model was added, the overall cavitation intensity increased and the reflux formed around the stone, which led to the block area under the stone model.This situation becomes more and more obvious with the gradual increase (curvature decrease) of 尉.The cavitation intensity of stone model is the highest in the center of focal region.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：R692.4

【参考文献】