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首页> 外文期刊>Ultrasound in Medicine and Biology >The Effect of Flow Acceleration on the Cyclic Variation of Blood Echogenicity Under Pulsatile Flow
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The Effect of Flow Acceleration on the Cyclic Variation of Blood Echogenicity Under Pulsatile Flow

机译：脉搏流动下血流加速对血液致电子性循环变化的影响

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It has been shown that the echogenicity of blood varies during a flow cycle under pulsatile flow both in vitro and in vivo. In general, the echogenicity of flowing whole blood increases during the early systole phase and then reduces to a minimum at late diastole. While it has been postulated that this cyclic variation is associated with the dynamics of erythrocyte aggregation, the mechanisms underlying this increasing echogenicity with flow velocity remain uncertain. The effect of flow acceleration has also been proposed as an explanation for this phenomenon, but no specific experiments have been conducted to test this hypothesis. In addition, the influence of ultrasonic attenuation on the cyclic variation of echogenicity requires clarification. In the present study, a Couette flow system was designed to simulate blood flowing with different acceleration patterns, and the flow velocity, attenuation, and backscattering coefficient were measured synchronously from 20%- and 40%-hematocrit porcine whole blood and erythrocyte suspensions using 35-MHz ultrasound transducers. The results showed ultrasonic attenuation exerted only minor effects on the echogenicity of blood under pulsatile flow conditions. Cyclic variations of echogenicity were clearly observed for whole blood with a hematocrit of 40%, but no variations were apparent for erythrocyte suspensions. The echogenicity did not appear to be enhanced when instantaneous acceleration was applied to flowing blood in any case. These findings show that flow acceleration does not promote erythrocyte aggregation, even when a higher peak velocity is applied to the blood. Comparison of the results obtained with different accelerations revealed that the cyclic variation in echogenicity observed during pulsatile blood flow may be jointly attributable to the effect of shear rate and the distribution of erythrocyte on aggregation.
机译：已经表明，在体外和体内，在脉动流的作用下，血液的回声性在一个流动循环中会变化。通常，流动的全血的回声性在收缩期早期增加，然后在舒张末期降低到最小。尽管已经假定这种周期性变化与红细胞聚集的动力学有关，但这种随流速回声增加的机制仍不确定。还提出了流动加速的影响来解释这种现象，但是还没有进行具体的实验来检验这种假设。此外，超声衰减对回声的周期性变化的影响需要澄清。在本研究中，设计了Couette流动系统来模拟不同加速模式下的血液流动，并使用35分别从20％和40％血细胞比容的猪全血和红细胞悬液中同步测量了流速，衰减和反向散射系数-MHz超声换能器。结果表明，在脉动流动条件下，超声衰减对血液的回声性影响很小。在血细胞比容为40％的全血中，明显观察到了回声的周期性变化，但对于红细胞悬液则没有明显变化。在任何情况下，对流动的血液施加瞬时加速度时，回声性似乎都没有增强。这些发现表明，即使对血液施加更高的峰值速度，血流加速也不会促进红细胞聚集。比较以不同加速度获得的结果，发现在脉动血流中观察到的回声性的周期性变化可能归因于剪切速率和红细胞分布对聚集的影响。

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