Low f-number photoacoustic lens for tight ultrasonic focusing and free-field micro-cavitation in water
Low f-number photoacoustic lens for tight ultrasonic focusing and free-field micro-cavitation in water
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DOI：
10.1063/1.4943369
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发表时间：
2016-03-07
影响因子：
4
通讯作者：
Baac, Hyoung Won
中科院分区：
文献类型：
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作者：
Lee, Taehwa;Ok, Jong G.;Baac, Hyoung Won
我们展示了一种在15 mhz频率下具有低f值0.61和高焦增益220的光声透镜，用于激光产生聚焦超声（LGFU），可实现水中的自由场微空化。由于超声聚焦紧密（横向光斑宽度为90 μ m，纵向光斑宽度为200 μ m，距离为9.2 mm），使用仅为1 mJ/脉冲（时间宽度为6 ns）的输入激光能量，透镜产生的峰值压力为20 MPa（正）。值得注意的是，我们使用这种透镜确认了自由场条件下的单脉冲微空化，这是以前用LGFU没有实现的。利用气泡半径、寿命和概率对自由场空化进行了监测和表征。我们的研究结果表明，在微尺度的点上，LGFU的振幅可以足够高于自由场空化的阈值，这是高精度空化治疗的关键一步。(C) 2016 AIP出版有限责任公司
We demonstrate a photoacoustic lens with a low f-number of 0.61 and a high focal gain of 220 at 15-MHz frequency for laser-generated focused ultrasound (LGFU), which enables free-field micro-cavitation in water. Due to tight ultrasonic focusing (90 mu m in lateral and 200 mu m in longitudinal spot widths at a distance of 9.2 mm), the lens produces a peak pressure of 20 MPa (positive) using an input laser energy of only 1 mJ/pulse (6-ns temporal width). Remarkably, we confirm single-pulsed micro-cavitation in a free-field condition by using this lens, which has not previously been achieved with LGFU. The free-field cavitation was monitored and characterized in terms of a bubble radius, a lifetime, and a probability. Our result demonstrates that LGFU amplitudes can be sufficiently higher than a threshold for free-field cavitation at a microscale spot, which is a crucial step for cavitation-based therapy with high precision. (C) 2016 AIP Publishing LLC.