Basic acoustic properties of microbubbles
Basic acoustic properties of microbubbles
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DOI：
10.1046/j.1540-8175.2002.00229.x
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发表时间：
2002-04-01
影响因子：
1.5
通讯作者：
Frinking, P
中科院分区：
文献类型：
--
作者：
de Jong, N;Bouakaz, A;Frinking, P
造影剂中的小（包膜）气泡会对外部振荡压力场产生体积脉动反应。根据超声波的强度，振动与所施加的声压呈线性或非线性相关。在低声压下，瞬时半径相对于所施加的外部压力场的振幅呈线性振荡。气泡的振荡受共振频率、阻尼系数和包膜特性等参数控制。对于较高的外场振幅，气泡的脉动变为非线性。散射超声波的频谱除了基频外，还包含发射频率的高次谐波。发射频率、气泡大小和非线性传播效应对谐波的产生有显著影响。对于暴露在更高声幅下的包膜气泡，其散射效率急剧增加并变为瞬态。散射频谱变宽，包含更高次谐波。这种结果是由于破裂、消失、气体含量变化等原因造成的。利用造影气泡的这些特定特性将为医学诊断的成像和分析开辟新的视角。
Small (encapsulated) gas bubbles in a contrast medium react to an external oscillating pressure field with volume pulsations. Depending on the magnitude of the ultrasound wave, the vibrations will be related either linearly or nonlinearly to the applied acoustic pressure. For low acoustic pressures, the instantaneous radius oscillates linearly in relation to the amplitude of the applied external pressure field. The oscillation of the bubble is governed by parameters such as resonance frequency, damping coefficients, and shell properties. For higher amplitudes of the external field, the pulsation of the bubbles becomes nonlinear. The spectrum of the scattered ultrasound wave also contains higher harmonics of the emitted frequency in addition to the fundamental frequency. The emitted frequency, bubble size, and nonlinear propagation effects have significant influence on the harmonic generation. For encapsulated bubbles exposed to even higher acoustic amplitudes, their scattering effectiveness increases dramatically and becomes transient. The scattered frequency spectrum broadens, containing higher harmonics. This consequence is due to rupture, disappearance, change of gas content, etc. Using these specific characteristics of the contrast bubbles will open new perspectives in imaging and analysis for medical diagnosis.