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中国物理学会期刊

多层膜结构载磁微泡声散射特性

CSTR: 32037.14.aps.71.20220847

Acoustic scattering properties of multilayer membrane structured magnetic microbubbles

CSTR: 32037.14.aps.71.20220847
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  • 搭载有磁性纳米颗粒的包膜微泡, 作为一种新型试剂在多模造影、溶栓治疗及靶向药物输运等多领域得以应用及研究. 常通过原位测量技术进行微泡研究, 而散射解析模型是声反演技术的基础. 由空气内核、均匀悬浮磁纳米颗粒的磁流体层及磷脂外层组成多膜层结构载磁微泡, 考虑磁流体密度变化及磷脂层黏弹性, 通过简正级数法求解多层结构微泡各区域的散射声场. 将载磁微泡散射模型与其他气泡进行对比, 并数值分析载磁微泡共振散射特性, 包括初始半径、磁纳米颗粒体积分数、磁流体层厚度及磷脂层特性参数等对微泡散射影响. 结果表明: 当膜层中磁纳米颗粒的体积分数α不超过0.1时, 颗粒对微泡共振散射的影响具有两面性, 既可增强也可减弱散射, 主要取决于微泡半径; 存在一个临界微泡半径值, 微泡半径超过此临界则颗粒将增强微泡散射, 反之减弱; 微泡半径一定, α不超过0.1时, α取值越高微泡散射越强; 膜层材料的拉梅常数和厚度越小的同尺度微泡散射更强. 该研究对载磁微泡结构优化设计、原位监测及诊疗应用有理论意义.

     

    Normal ultrasound contrast agents (UCAs) loaded with magnetic nanoparticles are called magnetic microbubbles (MMBs), which can be used in multimodal imaging, thrombolytic therapy, and targeted drug delivery. The MMBs are often studied by in situ measurement techniques, however scattering model is the basis of inversion techniques. Therefore, we develop a scattering model of multilayer structured MMBs with magnetic fluid inner layer and phospholipid outer layer, in which outer layer’s viscoelasticity and the effect of nanoparticles on inner layer’s density are considered, while scattered sound fields in each region are obtained by solving normal series. The MMB model is compared with other bubbles, and its acoustic scattering characteristics are analyzed numarically, including the effects of radius, magnetic nanoparticle volume fraction, inner layer thickness and outer layer characteristics parameters. The results show that when the volume fraction α of magnetic nanoparticles in the inner layer does not exceed 0.1, magnetic nanoparticles have a two-sided effect on resonant scattering of MMBs, depending mainly on its radius, and the bubble has a critical radius value. If the radius of MMBs exceeds this critical value, the particles will enhance scattering, on the contrary, if the radius of MMBs is smaller than this critical value, the particles will reduce scattering; for a given microbubble radius, when α is not more than 0.1, the larger the α value, the stronger the resonant scattering of MMBs will be; the smaller the thickness of the inner film layer and outer film layer or the Larmé constant, the stronger the scattering will be. This study provides a theoretical guidance for the optimal structural design of MMBs and its in situ monitoring and therapeutic applications.

     

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