Ultrasound contrast microbubbles in imaging and therapy: physical principles and engineering.
Ultrasound contrast microbubbles in imaging and therapy: physical principles and engineering.
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DOI：
10.1088/0031-9155/54/6/r01
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发表时间：
2009-03-21
影响因子：
3.5
通讯作者：
Ferrara KW
中科院分区：
文献类型：
--
作者：
Qin S;Caskey CF;Ferrara KW
微泡造影剂和相关的成像系统在过去的二十五年中得到了发展，起源于引入用于冠状动脉内注射的手动搅拌流体。在此期间，稳定壳和低扩散性气体材料已被纳入微泡，延长体外和体内的稳定性。同时，这些小气泡与超声波的相互作用已经被广泛研究，产生了振荡模型和日益复杂的成像策略。早期的研究认识到，来自微泡的回波包含微泡共振频率的倍数的频率。尽管无法分辨单个的微泡造影剂--假设它们的直径是微米级--但是来自这些造影剂的非线性回波被用于绘制灌注组织的区域并估计局部微血管流速。这种策略克服了以前的超声血流策略的基本限制;以前的基于多普勒的策略对毛细血管流动不敏感。此外，共振气泡的声波作用导致了有趣的物理现象，这些现象已经被广泛研究用于药物和基因递送。超声波压力可以增强气体扩散，快速地将药剂破碎成一组较小的气泡或将微泡移位到血管壁。微泡的超声作用还可以产生液体射流和局部剪切应力，从而改变生物膜并促进运输。本文就这些药物的物理特性、微泡成像模式、微泡振荡模型以及微泡与内皮细胞的相互作用等方面进行综述。
Microbubble contrast agents and the associated imaging systems have developed over the past twenty-five years, originating with manually-agitated fluids introduced for intra-coronary injection. Over this period, stabilizing shells and low diffusivity gas materials have been incorporated in microbubbles, extending stability in vitro and in vivo. Simultaneously, the interaction of these small gas bubbles with ultrasonic waves has been extensively studied, resulting in models for oscillation and increasingly sophisticated imaging strategies. Early studies recognized that echoes from microbubbles contained frequencies that are multiples of the microbubble resonance frequency. Although individual microbubble contrast agents cannot be resolved—given that their diameter is on the order of microns—nonlinear echoes from these agents are used to map regions of perfused tissue and to estimate the local microvascular flow rate. Such strategies overcome a fundamental limitation of previous ultrasound blood flow strategies; the previous Doppler-based strategies are insensitive to capillary flow. Further, the insonation of resonant bubbles results in interesting physical phenomena that have been widely studied for use in drug and gene delivery. Ultrasound pressure can enhance gas diffusion, rapidly fragment the agent into a set of smaller bubbles or displace the microbubble to a blood vessel wall. Insonation of a microbubble can also produce liquid jets and local shear stress that alter biological membranes and facilitate transport. In this review, we focus on the physical aspects of these agents, exploring microbubble imaging modes, models for microbubble oscillation and the interaction of the microbubble with the endothelium.