It is well known that the scatter of ultrasound by blood is mainly attributed to red blood cells (RBCs) and RBC aggregation. In the present review, researches of hemodynamic influence on RBC aggregation and ultrasound backscatter from blood were overviewed. A mock flow loop and a cylindrical chamber were employed to produce various blood flows, such as pulsatile, oscillatory, and rotational flow. The “black hole” (BLH), a dark hole at the tube center surrounded by bright zone in the cross sectional B-mode image and “bright collapsing ring” (BRCR) phenomena, appearance of bright ring at the periphery and collapse of it at the center during a pulsatile cycle, were observed under pulsatile flow. The combined effects of shear rate and flow acceleration on RBC aggregation were suggested as a possible mechanism for these phenomena. The stroke volume-dependence of the “bright ring” phenomenon under oscillatory flow could also be explained by flow acceleration. The enveloped echo images from rotational flow in a compact blood chamber showed the spatial and temporal variations of RBC aggregation, which varied with the mammalian species. In the stenotic model, it was found that the echogenic variation increased locally at a distance of three tube diameters downstream from the stenosis during decelerating period, which was proposed to be mainly due to flow turbulence. The similar ‘bright ring’ was also observed fromin vivo human carotid artery in harmonic imaging.

中文翻译：

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流动血液中红细胞动态行为的超声可视化

众所周知，血液对超声波的散射主要归因于红细胞 (RBC) 和红细胞聚集。在本综述中，概述了血液动力学对红细胞聚集和血液超声反向散射的影响的研究。模拟流动回路和圆柱形腔室用于产生各种血流，例如脉动、振荡和旋转流。“黑洞”（BLH），横截面B模式图像中被亮区包围的管中心的黑洞和“亮塌陷环”（BRCR）现象，在外围出现亮环并坍塌在脉动循环期间的中心，在脉动流下观察到。剪切速率和流动加速对红细胞聚集的综合影响被认为是这些现象的可能机制。振荡流下“亮环”现象的每搏量依赖性也可以用流加速来解释。来自紧凑血室中旋转流的包络回波图像显示了 RBC 聚集的空间和时间变化，这随哺乳动物的种类而变化。在狭窄模型中，发现减速期狭窄下游三个管径处回声变化局部增加，这被认为主要是由于流动湍流。在谐波成像中也从体内人颈动脉观察到类似的“亮环”。来自紧凑血室中旋转流的包络回波图像显示了 RBC 聚集的空间和时间变化，这随哺乳动物的种类而变化。在狭窄模型中，发现减速期狭窄下游三个管径处回声变化局部增加，这被认为主要是由于流动湍流。在谐波成像中也从体内人颈动脉观察到类似的“亮环”。来自紧凑血室中旋转流的包络回波图像显示了 RBC 聚集的空间和时间变化，这随哺乳动物的种类而变化。在狭窄模型中，发现减速期狭窄下游三个管径处回声变化局部增加，这被认为主要是由于流动湍流。在谐波成像中也从体内人颈动脉观察到类似的“亮环”。