Ultrasound-mediated destruction of contrast microbubbles used for medical imaging and drug delivery
Ultrasound-mediated destruction of contrast microbubbles used for medical imaging and drug delivery
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DOI：
10.1063/1.2011468
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发表时间：
2005-10-01
影响因子：
4.6
通讯作者：
Sarkar, K
中科院分区：
文献类型：
--
作者：
Chatterjee, D;Jain, P;Sarkar, K
微米大小的气泡被表面活性物质的稳定层包裹，用于医学超声成像和药物输送。超声在体内刺激它们的破坏在这两种应用中都起着关键作用。我们通过测量超声波通过造影剂的衰减来研究市售造影剂中微泡的破坏过程。测量由无聚焦换能器（中心频率为5 MHz）在50、100和200 hz脉冲重复频率（PRF）下的单周期脉冲进行，占空比分别为0.001%、0.002%和0.004%。在低激励下，衰减随时间增加。随着激发强度的增加，衰减强度随时间的增加而减小，表明微泡已被破坏。所有三种PRFs都有一个临界压力幅值（类似于1.2 MPa），低于此值没有明显的气泡破坏。在临界压力幅值以上，破坏速率取决于激发水平。但在高压振幅下，破坏与激励压力幅值无关。结果表明，通过气泡衰减特征可以确定两种不同的气泡破坏机制，即扩散缓慢溶解和灾难性壳破裂。详细讨论了不同的模式及其在医学应用中的含义。(c) 2005年美国物理研究所。
Micron-size bubbles encapsulated by a stabilizing layer of surface-active materials are used in medical ultrasound imaging and drug delivery. Their destruction stimulated by ultrasound in vivo plays a critical role in both applications. We investigate the destruction process of microbubbles in a commercially available contrast agent by measuring the attenuation of ultrasound through it. The measurement is performed with single-cycle bursts from an unfocused transducer (with a center frequency of 5 MHz) for varying pressure amplitudes at 50-, 100-, and 200-Hz pulse repetition frequencies (PRF) with duty cycles 0.001%, 0.002%, and 0.004%, respectively. At low excitation, the attenuation is found to increase with time. With increased excitation level, the attenuation level decreases with time, indicating destruction of microbubbles. There is a critical pressure amplitude (similar to 1.2 MPa) for all three PRFs, below which there is no significant bubble destruction. Above the critical pressure amplitudes the rate of destruction depends on excitation levels. But at high-pressure amplitudes the destruction becomes independent of excitation pressure amplitude. The results are interpreted to identify two different mechanisms of bubble destruction by its signature in attenuation, namely, slow dissolution by diffusion and catastrophic shell rupture. The different modes are discussed in detail with their implications in medical applications. (c) 2005 American Institute of Physics.