ACOUSTIC BEHAVIOR OF HALOBACTERIUM SALINARUM GAS VESICLES IN THE HIGH-FREQUENCY RANGE: EXPERIMENTS AND MODELING
ACOUSTIC BEHAVIOR OF HALOBACTERIUM SALINARUM GAS VESICLES IN THE HIGH-FREQUENCY RANGE: EXPERIMENTS AND MODELING
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DOI：
10.1016/j.ultrasmedbio.2016.12.020
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发表时间：
2017-05-01
影响因子：
2.9
通讯作者：
Shapiroz, Mikhail G.
中科院分区：
文献类型：
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作者：
Cherin, Emmanuel;Melis, Johan M.;Shapiroz, Mikhail G.
气泡是一类新型的、独特的亚微米级生物超声造影剂，其声学特性尚未完全阐明。在这项研究中，我们调查了声崩溃的压力和行为的盐盐杆菌气泡在发射中心频率范围从12.5到27.5兆赫。在所有频率下，声崩溃压力都在550 kPa以上，比在静水条件下观察到的临界压力高9倍。我们说明，气泡的行为非线性时，暴露于超声波在入射压力范围从160千帕的崩溃压力，并产生二次谐波振幅22至26分贝以下的基本在介质中的粘度范围从0.89至8 mPa. s。使用Rayleigh-Plesset型模型解释屈曲和动态有限元分析进行的模拟表明，屈曲是谐波产生背后的机制。我们发现，在20 MHz和瑞利-Plesset模型预测的二次谐波相对于基本测量的水平之间有很好的协议。有限元模拟扩展这些发现的非球形几何形状，证实了声屈曲压力对应于流体静力学条件下的临界压力，并支持有限的气体流量在压缩阶段的GV壳在频率范围内调查的假设。从模拟，GV带宽限制散射的估计表明，一个单一的GV具有散射截面的红细胞。这些发现将为基于GV的造影剂和脉冲序列的开发提供信息，以优化超声检测。(C)2017年世界医学和生物学超声联合会。
Gas vesicles (GVs) are a new and unique class of biologically derived ultrasound contrast agents with sub-micron size whose acoustic properties have not been fully elucidated. In this study, we investigated the acoustic collapse pressure and behavior of Halobacterium salinarum gas vesicles at transmit center frequencies ranging from 12.5 to 27.5 MHz. The acoustic collapse pressure was found to be above 550 kPa at all frequencies, ninefold higher than the critical pressure observed under hydrostatic conditions. We illustrate that gas vesicles behave non-linearly when exposed to ultrasound at incident pressure ranging from 160 kPa to the collapse pressure and generate second harmonic amplitudes of 22 to 26 dB below the fundamental in media with viscosities ranging from 0.89 to 8 mPa.s. Simulations performed using a Rayleigh-Plesset-type model accounting for buckling and a dynamic finite-element analysis suggest that buckling is the mechanism behind the generation of harmonics. We found good agreement between the level of second harmonic relative to the fundamental measured at 20 MHz and the Rayleigh-Plesset model predictions. Finite-element simulations extended these findings to a non-spherical geometry, confirmed that the acoustic buckling pressure corresponds to the critical pressure under hydrostatic conditions and support the hypothesis of limited gas flow across the GV shell during the compression phase in the frequency range investigated. From simulations, estimates of GV bandwidth-limited scattering indicate that a single GV has a scattering cross section comparable to that of a red blood cell. These findings will inform the development of GV-based contrast agents and pulse sequences to optimize their detection with ultrasound. (C) 2017 World Federation for Ultrasound in Medicine & Biology.