Observing Bubble Cavitation by Back-Propagation of Acoustic Emission Signals
Observing Bubble Cavitation by Back-Propagation of Acoustic Emission Signals
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DOI：
10.1109/tuffc.2019.2897983
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发表时间：
2019-02
期刊：
影响因子：
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通讯作者：
R. Koda;Takumu Origasa;Toshitaka Nakajima;Y. Yamakoshi
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文献类型：
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作者：
R. Koda;Takumu Origasa;Toshitaka Nakajima;Y. Yamakoshi
高强度超声照射产生的微泡空化现象的时间和空间分辨观测是提高超声辅助给药系统效率和疗效的关键。提出了一种利用声空化发射（ACE）信号反向传播图像重建技术测量气泡空化的方法。利用超声记录设备对气泡进行高强度聚焦超声波（泵波）同步照射，获取气泡空化过程中气泡辐射二次波时产生的射频信号的定时。通过超声波反向传播和振幅反卷积重建ACE信号源。通过改变泵浦波的声压，将该方法应用于超声造影剂的微泡中。通过对虚拟声源的调幅信号进行仿真，验证了该方法时间分辨率的可靠性。ACE信号的时间跃迁表现出亚微秒级的信号强度波动。从该方法的幅值信号图像和瞬时频率图像重构中，可以直观地看到两种不同的ACE现象。一种是低强度超声条件下非线性振荡的谐波和超谐波分量产生的节拍信号的周期性模式。二是在高强度超声条件下辐照的非周期性时空分布。
Temporal- and spatial-resolved observations of microbubble cavitation generated through high-intensity ultrasound irradiation are key in improving both the efficiency and efficacy of ultrasound-assisted drug delivery systems. A method of measuring bubble cavitation applying an image-reconstruction technique of back-propagation of an acoustic cavitation emission (ACE) signal is proposed. A high-intensity focused ultrasound wave (pump wave) irradiates the bubble synchronously using ultrasound recording equipment to acquire the timing of the RF signal, which is produced when the bubble radiates a secondary wave during bubble cavitation. The ACE signal source is reconstructed through ultrasound-wave back-propagation followed by amplitude deconvolution. The proposed method was applied to microbubbles of an ultrasound contrast agent by changing the sound pressure of the pump wave. The method reliability of the temporal resolution was verified by simulating the amplitude-modulated signal of the virtual sound source. The temporal transition of the ACE signal exhibited sub-microsecond-order fluctuations in the signal intensity. From the amplitude signal image and the instantaneous frequency image reconstruction of the proposed method, two different ACE phenomena were visualized. One is the periodic pattern by the beat signals from the harmonic and ultraharmonic component of nonlinear oscillation under low-intensity ultrasound conditions. The other is the nonperiodic temporal and spatial distributions of this irradiation under high-intensity ultrasound conditions.