Investigating the significance of multiple scattering in ultrasound contrast agent particle populations
Investigating the significance of multiple scattering in ultrasound contrast agent particle populations
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DOI：
10.1109/tuffc.2005.1563278
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发表时间：
2005-12-01
影响因子：
3.6
通讯作者：
Saffari, N
中科院分区：
文献类型：
--
作者：
Stride, E;Saffari, N
大多数描述微泡超声造影剂行为的现有模型考虑单个孤立的微泡悬浮在无限介质中。通过对单个微泡的结果求和并忽略多次散射效应来预测微泡群体的行为。本研究的目的是确定微泡群体中多重散射的意义，并确定是否需要替代方法。在第一部分的工作中，线性模型推导出近似识别的条件下，多重散射可能是预期的。一个非线性模型的声音在微泡悬浮液中的传播，然后被开发和用于检查在较高的声压力下的多重散射。宽带衰减测量描述了两种不同类型的微泡悬浮液（白蛋白封装的三氟丙烷和共聚物封装的异丁烷），以确定是否可以观察到多次散射实验。模拟工作的结果表明，在中等浓度（106个微泡/ml）下，如可能存在于体内，多重散射效应将是可辨别的。然而，只有当群体包含足够比例的在其共振频率下激发的相对大（> 4 μ m半径）的微泡时，对悬浮液中的衰减的影响才是显著的。这也被发现是实验的情况。这些发现可能对超声造影剂的表征及其在定量诊断技术中的应用具有重要意义。
The majority of the existing models describing the behavior of microbubble ultrasound contrast agents consider single, isolated microbubbles suspended in infinite media. The behavior of a microbubble population is predicted by summing the results for single microbubbles and ignoring multiple scattering effects. The aim of this investigation is to determine the significance of multiple scattering in microbubble populations and establish whether an alternative approach is required. In the first part of the work, linear models are derived to identify approximately the conditions under which multiple scattering may be expected. A nonlinear model for sound propagation in a microbubble suspension then is developed and used to examine multiple scattering at higher insonation pressures. Broadband attenuation measurements are described for two different types of microbubble suspension (albumin encapsulated octofluropropane and copolymer encapsulated isobutane) to ascertain whether or not multiple scattering may be observed experimentally. The results from the simulation work indicate that multiple scattering effects would be discernible at moderate concentrations (106 microbubbles/ml) such as may be present in vivo. The effect upon attenuation in the suspension would be pronounced, however, only if the population contained a sufficient proportion of relatively large (> 4 mu m radius) microbubbles excited at their resonance frequency. This also is found to be the case experimentally. These findings may have important implications for the characterization of ultrasound contrast agents and their use in quantitative diagnostic techniques.