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首页> 外文期刊>IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control >Correlation of rupture dynamics to the nonlinear backscatter response from polymer-shelled ultrasound contrast agents
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Correlation of rupture dynamics to the nonlinear backscatter response from polymer-shelled ultrasound contrast agents

机译：聚合物壳超声造影剂的破裂动力学与非线性反向散射响应的相关性

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摘要

Polymer-shelled ultrasound contrast agents (UCAs) may expel their encapsulated gas subject to ultrasound- induced shell buckling or rupture. Nonlinear oscillations of this gas bubble can produce a subharmonic component in the ultrasound backscatter. This study investigated the relationship between this gas-release mechanism and shell-thickness??? to???radius ratios (STRRs) of polymer-shelled UCAs. Three types of polylactide-shelled UCAs with STRRs of 7.5, 40, and 100 nm/??m were studied. Each UCA population had a nominal mean diameter of 2 ??m. UCAs were subjected to increasing static overpressure ranging from 2 to 330 kPa over a duration of 2 h in a custom-designed test chamber while being imaged using a 200?? magnification video microscope at a frame rate of 5 frames/s. Digitized video images were binarized and processed to obtain the cross-sectional area of individual UCAs. Integration of the normalized cross-sectional area over normalized time, defined as buckling factor (Bf), provided a dimensionless parameter for quantifying and comparing the degree of pre-rupture buckling exhibited by the UCAs of different STRRs in response to overpressure. The UCAs with an STRR of 7.5 nm/??m exhibited a distinct shell-buckling phase before shell rupture (Bf
机译：聚合物外壳的超声造影剂（UCA）可能会将其封装的气体排出体外，并受到超声引起的外壳屈曲或破裂。该气泡的非线性振荡会在超声反向散射中产生次谐波分量。这项研究调查了这种气体释放机理与壳厚度之间的关系。聚合物带壳的UCA与半径之比（STRRs）。研究了STRR分别为7.5、40和100 nm /λm的三种类型的带聚丙交酯壳的UCA。每个UCA人口的标称平均直径为2 ?? m。 UCA在定制设计的测试室中经过2小时的持续不断地承受2至330 kPa的静态超压，同时使用200升放大视频显微镜，帧率为5帧/秒。将数字化的视频图像进行二值化处理，以获得单个UCA的横截面积。归一化横截面积在归一化时间内的积分（定义为屈曲因子（Bf））为量化和比较不同STRR的UCA响应超压所表现出的破裂前屈曲的程度提供了无量纲参数。 STRR为7.5 nm /？m的UCA在壳破裂之前表现出明显的壳屈曲相（Bf

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