Jet formation and shock wave emission during collapse of ultrasound-induced cavitation bubbles and their role in the therapeutic applications of high-intensity focused ultrasound
Jet formation and shock wave emission during collapse of ultrasound-induced cavitation bubbles and their role in the therapeutic applications of high-intensity focused ultrasound
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DOI：
10.1088/0031-9155/50/20/004
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发表时间：
2005-10-21
影响因子：
3.5
通讯作者：
Matsumoto, Y
中科院分区：
文献类型：
--
作者：
Brujan, EA;Ikeda, T;Matsumoto, Y
研究了高强度聚焦超声短脉冲在刚性边界附近产生的惯性空化气泡的动力学，以便更好地理解气泡破裂过程中射流形成和冲击波发射在超声治疗应用中的作用。通过高达200万帧/秒的高速摄影和声学测量以及数值计算来研究气泡动力学。本研究的重要参数是无量纲距离，伽马，它被定义为气泡中心在最大膨胀时的距离，用最大气泡半径进行缩放。采用高速摄影技术观察了气泡的运动和气泡破裂时形成的液体射流的速度。水听器测量用于确定气泡反弹时所发出的冲击波的压力和持续时间。计算得到了气泡壁、最大速度和再入射流动能随时间的变化。关于气泡的形状历史和平移运动，实验数据与数值数据的比较是有利的。在气泡崩塌的能量平衡中，声能占最大的单个量。在距离发射中心10mm处测量的冲击波能量与空化泡能量之比在gamma = 1.55处为1:24 .4，在gamma = 1处为1:35 .5。在此距离上，冲击波压力范围为0.122 MPa，伽马值为1，至0.162 MPa，伽马值为1.55，半峰值持续时间为87 ns。最大射流速度范围为γ = 1时的27 m s（-1）到γ = 1.55时的36 m s（-1）。gamma < 1.2时，再入射流在附近边界产生的冲击压力大于50 MPa。我们讨论了结果对高强度聚焦超声治疗应用的意义。
The dynamics of inertial cavitation bubbles produced by short pulses of high-intensity focused ultrasound near a rigid boundary are studied to get a better understanding of the role of jet formation and shock wave emission during bubble collapse in the therapeutic applications of ultrasound. The bubble dynamics are investigated by high-speed photography with up to 2 million frames/s and acoustic measurements, as well as by numerical calculations. The significant parameter of this study is the dimensionless stand-off, gamma, which is defined as the distance of the bubble Centre at its maximum expansion scaled by the maximum bubble radius. High-speed photography is applied to observe the bubble motion and the velocity of the liquid jet formed during bubble collapse. Hydrophone measurements are used to determine the pressure and the duration of the shock wave emitted during bubble rebound. Calculations yield the variation with time of the bubble wall, the maximum velocity and the kinetic energy of the re-entrant jet. The comparisons between experimental and numerical data are favourable with regard to both shape history and translational motion of the bubble. The acoustic energy constitutes the largest individual amount in the energy balance of bubble collapse. The ratio of the shock wave energy, measured at 10 mm from the emission centre, to the cavitation bubble energy was 1:2.4 at gamma = 1.55 and 1:3.5 at gamma 1. At this distance, the shock wave pressure ranges from 0.122 MPa, at gamma 1, to 0.162 MPa, at gamma = 1.55, and the temporal duration at the half maximum level is 87 ns. The maximum jet velocity ranges from 27 m s(-1), at gamma = 1, to 36 m s(-1), at gamma = 1.55. For gamma < 1.2, the re-entrant jet can generate an impact pressure on the nearby boundary larger than 50 MPa. We discuss the implications of the results for the therapeutic applications of high-intensity focused ultrasound.