Zhong P, Lin H, Xi X, Zhu S, Bhogte E S
Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA.
J Acoust Soc Am. 1999 Mar;105(3):1997-2009. doi: 10.1121/1.426733.
A method of generating in situ shock wave-inertial microbubble interaction by a modified electrohydraulic shock wave lithotripter is proposed and tested in vitro. An annular brass ellipsoidal reflector (thickness = 28 mm) that can be mounted on the aperture rim of a Dornier XL-1 lithotripter was designed and fabricated. This ring reflector shares the same foci with the XL-1 reflector, but is 15 mm short in major axis. Thus, a small portion of the spherical shock wave, generated by a spark discharge at the first focus (F1) of the reflector, is reflected and diffracted by the ring reflector, producing a weak shock wave approximately 8.5 microseconds in front of the lithotripter pulse. Based on the configuration of the ring reflector (different combinations of six identical segments), the peak negative pressure of the preceding weak shock wave at the second focus (F2) can be adjusted from -0.96 to -1.91 MPa, at an output voltage of 25 kV. The preceding shock wave induces inertial microbubbles, most of which expand to a maximum size of 100-200 microns, with a few expanding up to 400 microns before being collapsed in situ by the ensuing lithotripter pulse. Physical characterizations utilizing polyvinylidene difluoride (PVDF) membrane hydrophone, high-speed shadowgraph imaging, and passive cavitation detection have shown strong secondary shock wave emission immediately following the propagating lithotripter shock front, and microjet formation along the wave propagation direction. Using the modified reflector, injury to mouse lymphoid cells is significantly increased at high exposure (up to 50% with shock number > 100). With optimal pulse combination, the maximum efficiency of shock wave-induced membrane permeabilization can be enhanced substantially (up to 91%), achieved at a low exposure of 50 shocks. These results suggest that shock wave-inertial microbubble interaction may be used selectively to either enhance the efficiency of shock wave-mediated macromolecule delivery at low exposure or tissue destruction at high exposure.
提出了一种利用改进型液电冲击波碎石机原位产生冲击波-惯性微泡相互作用的方法，并在体外进行了测试。设计并制造了一个环形黄铜椭圆形反射器（厚度 = 28 毫米），它可以安装在多尼尔 XL-1 碎石机的孔径边缘。这个环形反射器与 XL-1 反射器共享相同的焦点，但长轴短 15 毫米。因此，由反射器第一焦点（F1）处的火花放电产生的一小部分球面冲击波被环形反射器反射和衍射，在碎石机脉冲前约 8.5 微秒产生一个弱冲击波。基于环形反射器的结构（六个相同部分的不同组合），在 25 kV 的输出电压下，第二焦点（F2）处先前弱冲击波的峰值负压可在 -0.96 至 -1.91 MPa 之间调节。先前的冲击波诱导惯性微泡，其中大部分膨胀到最大尺寸 100 - 200 微米，少数膨胀到 400 微米，然后被随后的碎石机脉冲原位坍塌。利用聚偏二氟乙烯（PVDF）膜水听器、高速阴影成像和被动空化检测进行的物理表征表明，在传播的碎石机冲击波前沿之后立即有强烈的二次冲击波发射，并且沿波传播方向形成微射流。使用改进的反射器，在高暴露（冲击波次数 > 100 时高达 50%）下，对小鼠淋巴细胞的损伤显著增加。通过最佳脉冲组合，在低暴露 50 次冲击时，冲击波诱导的膜通透性的最大效率可大幅提高（高达 91%）。这些结果表明，冲击波-惯性微泡相互作用可被选择性地用于在低暴露下提高冲击波介导的大分子递送效率或在高暴露下进行组织破坏。
