The natural frequency of nonlinear oscillation of ultrasound contrast agents in microvessels
The natural frequency of nonlinear oscillation of ultrasound contrast agents in microvessels
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DOI：
10.1016/j.ultrasmedbio.2006.12.009
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发表时间：
2007-07-01
影响因子：
2.9
通讯作者：
Ferrara, Katherine W.
中科院分区：
文献类型：
--
作者：
Qin, Shengping;Ferrara, Katherine W.
超声造影剂(UCAS)因其在生理、分子成像和药物传递方面的应用而受到广泛的研究。微血管内UCA振荡固有频率的预测越来越受到人们的关注。据我们所知，现有的预测微血管内UCA振荡固有频率的模型均采用线性近似，并将血管壁视为刚性边界。在超声成像药物和基因传递的潜在应用中，小血管的顺应性可能对气泡的振荡起重要作用。这项工作的目的是提供一个集总参数模型来研究微血管中UCA非线性振动的固有频率。考虑了三种类型的血管状况：即僵硬的血管、正常的顺应性血管和与肿瘤血管相对应的僵硬增加的血管。详细考察了半径小于100微米的容器内相应的气泡振荡频率。当半径为4um的气泡被限制在一个柔顺的容器中(内径为5am，长度为100um)时，气泡振动的固有频率比无界场中气泡的固有频率增加了1.7倍。柔顺容器中气泡振动的固有频率随容器尺寸的减小而增大，随容器刚性值的增大而减小。该模型建议在超声造影和药物输送中，应综合考虑造影剂的大小、血管大小分布和血管类型来选择发射频率。(电子邮件：spqin@ucdavis.edu)(C)2007年世界医学和生物学超声联合会。
Ultrasound contrast agents (UCAs) are under intensive investigation for their applications in physiological and molecular imaging and drug delivery. Prediction of the natural frequency of the oscillation of UCAs in microvessels has drawn increasing attention. To our knowledge, the existing models to predict the natural frequency of oscillation of UCAs in microvessels all apply the linear approximation and treat the blood vessel wall as a rigid boundary. In the potential applications of ultrasound imaging drug and gene delivery, the compliance of small vessels may play an important role in the bubble's oscillation. The goal of this work is to provide a lumped-parameter model to study the natural frequency of nonlinear oscillation of UCAs in microvessels. Three types of the blood vessel conditions have been considered: i.e., rigid vessels, normal compliable vessels and vessels with increasing stiffness that could correspond to tumor vasculature. The corresponding bubble oscillation frequencies in vessels with a radius less than 100 mu m are examined in detail. When a bubble with a radius of 4 um is confined in a compliable vessel (inner radius 5 Am and length 100 um), the natural frequency of bubble oscillation increases by a factor of 1.7 compared with a bubble in an unbounded field. The natural frequency of oscillation of a bubble in a compliable vessel increases with decreasing vessel size while decreasing with increasing values of vessel rigidity. This model suggests that contrast agent size, blood vessel size distribution and the type of vasculature should comprehensively be considered for choosing the transmitted frequency in ultrasound contrast imaging and drug delivery. (E-mail: spqin@ucdavis.edu) (C) 2007 World Federation for Ultrasound in Medicine & Biology.