Removal of Residual Nuclei Following a Cavitation Event Using Low-Amplitude Ultrasound
Removal of Residual Nuclei Following a Cavitation Event Using Low-Amplitude Ultrasound
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DOI：
10.1109/tuffc.2014.006316
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发表时间：
2014-10-01
影响因子：
3.6
通讯作者：
Hall, Timothy L.
中科院分区：
文献类型：
--
作者：
Duryea, Alexander P.;Cain, Charles A.;Hall, Timothy L.
在空化事件发生后，微观残余气泡核可以持续1s左右。这些气泡会限制超声波治疗的效果，如冲击波碎石术和组织碎裂术，因为它们会减弱在其形成后到达的脉冲，并在离散的一组位置（空化记忆）产生重复的空化活动。在这里，我们探索了一种去除空化事件后这些残余气泡的策略，使用低振幅超声脉冲来刺激气泡合并。所有实验均在除气水中进行，并采用高速摄影进行监测。在每种情况下，使用2 mhz的histotripsy换能器启动空化活动（空化气泡云），其崩溃产生残余气泡核的人口。然后使用来自单独的500 khz换能器的1 ms脉冲对残余核种群进行超声处理，我们称之为气泡去除脉冲。测试了0 ~ 1.7 MPa的气泡去除脉冲幅度，并计算了气泡去除后残留在现场的气泡阴影的背光面积，以量化效果。研究发现，存在一个理想的振幅范围（约180 ~ 570 kPa），在这个范围内，气泡去除脉冲刺激残余气泡核的聚集和随后的聚并，有效地将它们从场中去除。气泡去除脉冲序列的进一步优化将为基于空泡的超声治疗（如冲击波碎石术和组织切片术）提供辅助，减轻目前限制其疗效的残余气泡核的影响。
Microscopic residual bubble nuclei can persist on the order of 1 s following a cavitation event. These bubbles can limit the efficacy of ultrasound therapies such as shock wave lithotripsy and histotripsy, because they attenuate pulses that arrive subsequent to their formation and seed repetitive cavitation activity at a discrete set of sites (cavitation memory). Here, we explore a strategy for the removal of these residual bubbles following a cavitation event, using low-amplitude ultrasound pulses to stimulate bubble coalescence. All experiments were conducted in degassed water and monitored using high-speed photography. In each case, a 2-MHz histotripsy transducer was used to initiate cavitation activity (a cavitational bubble cloud), the collapse of which generated a population of residual bubble nuclei. This residual nuclei population was then sonicated using a 1 ms pulse from a separate 500-kHz transducer, which we term the bubble removal pulse. Bubble removal pulse amplitudes ranging from 0 to 1.7 MPa were tested, and the backlit area of shadow from bubbles remaining in the field following bubble removal was calculated to quantify efficacy. It was found that an ideal amplitude range exists (roughly 180 to 570 kPa) in which bubble removal pulses stimulate the aggregation and subsequent coalescence of residual bubble nuclei, effectively removing them from the field. Further optimization of bubble removal pulse sequences stands to provide an adjunct to cavitation-based ultrasound therapies such as shock wave lithotripsy and histotripsy, mitigating the effects of residual bubble nuclei that currently limit their efficacy.