Optical and acoustical observations of the effects of ultrasound on contrast agents
Optical and acoustical observations of the effects of ultrasound on contrast agents
复制标题
DOI：
10.1109/58.741536
复制
发表时间：
1999-01-01
影响因子：
3.6
通讯作者：
Ferrara, KW
中科院分区：
文献类型：
--
作者：
Dayton, PA;Morgan, KE;Ferrara, KW
超声造影剂和药物递送的封装微泡的最佳使用需要理解影响造影剂回声和持续性的一组复杂现象。随着使用的视频显微镜系统耦合到一个超声流幻影或一个腔室声穿透静止的气泡，我们表明，超声封装微泡有显着的影响。体外研究表明，一系列超声脉冲可以改变白蛋白壳气泡的结构，启动各种气泡破坏机制或产生改变回波频谱的聚集。在该分析中，将光学观察到的变化与声学观察到的白蛋白和脂壳制剂的变化进行比较。我们表明，当声与窄带脉冲在几百千帕的声压，磷脂壳的气泡可以经历至少15%的净半径波动，和白蛋白壳的气泡最初表现出受约束的膨胀和收缩。如果白蛋白壳中含有空气，壳最初可能不会经历表面张力，因此，回声的变化更显着与重复脉冲;。一组观察造影剂破坏，其中包括缓慢扩散的气体通过壳和壳缺陷的形成，然后气体快速扩散到周围的液体。这些观察结果表明，这些造影剂中使用的低溶解度气体可以在溶液中持续几百毫秒，在高脉冲重复频率和低压力下，造影剂的回波可以受到二次辐射力的影响。二次辐射力是这些实验条件下一个有吸引力的闹剧，创造具有独特的回声特征和延长的持久性聚集。来自聚集体的散射回波比来自单个气泡的回波强几倍，并且更窄。
Optimal use of encapsulated microbubbles for ultrasound contrast agents and drug delivery requires an understanding of the complex set of phenomena that affect the contrast agent echo and persistence. With the use of a video microscopy system coupled to either an ultrasound flow phantom or a chamber for insonifying stationary bubbles, we show that ultrasound has significant effects on encapsulated microbubbles. In vitro studies show that a train of ultrasound pulses can alter the structure of an albumin-shelled bubble, initiate various mechanisms of bubble destruction or produce aggregation that changes the echo spectrum. In this analysis, changes observed optically are compared with those observed acoustically for both albumin and lipid-shelled agents. We show that, when insonified with a narrowband pulse at an acoustic pressure of several hundred kPa, a phospholipid-shelled bubble can undergo net radius fluctuations of at least 15%; and an albumin-shelled bubble initially demonstrates constrained expansion and contraction. If the albumin shell contains air, the shell may not initially experience surface tension; therefore, the echo changes more significantly with repeated pulsing;.A set of observations of contrast agent destruction is presented, which includes the slow diffusion of gas through the shell and formation of a shell defect followed by rapid diffusion of gas into the surrounding liquid. These observations demonstrate that the low-solubility gas used in these agents can persist for several hundred milliseconds in solution.With the transmission of a high-pulse repetition rate and a low pressure, the echoes fi om contrast agents can be affected by secondary radiation force. Secondary radiation force is an attractive farce for these experimental conditions, creating aggregates with distinct echo characteristics and extended persistence. The scattered echo from an aggregate is several times stronger and more narrowband than echoes from individual bubbles.