Sigel B, Machi J, Beitler J C, Justin J R
Radiology. 1983 Sep;148(3):799-802. doi: 10.1148/radiology.148.3.6878705.
The role of red cell aggregation as a cause of ultrasonic echogenicity in flowing blood was evaluated by in vitro experiments using fresh human blood. Blood was circulated in tubes of varying diameter (12 mm to 6 mm). In all experiments, echogenicity increased as blood approached static conditions. Echogenicity was greater in tubes with a larger diameter over the same range of blood velocity. However, echogenicity in tubes of various diameters was the same when evaluated in terms of shear rate. Thus, shear rate and not velocity is the flow condition that determines echogenicity. Since shear rate determines the degree of red cell aggregation, while other conditions affecting red cell aggregation (hematocrit, erythrocyte membrane conditions, and plasma macromolecules) are held constant, we conclude that these results provide additional evidence that red cell aggregation is a cause of echogenicity in flowing blood. Furthermore, a red cell aggregation mechanism for blood-flow echogenicity would explain the increased prominence of internal echoes in lower shear rate venous blood flow compared with those of higher shear rate arterial blood flow.
通过使用新鲜人血的体外实验，评估了红细胞聚集作为流动血液中超声回声源的作用。血液在不同直径（12毫米至6毫米）的管子中循环。在所有实验中，随着血液接近静态，回声增强。在相同的血流速度范围内，直径较大的管子中的回声更强。然而，就剪切率而言，不同直径管子中的回声是相同的。因此，决定回声的血流条件是剪切率而非速度。由于剪切率决定红细胞聚集程度，而影响红细胞聚集的其他条件（血细胞比容、红细胞膜状况和血浆大分子）保持不变，我们得出结论，这些结果提供了额外证据，证明红细胞聚集是流动血液中回声的一个原因。此外，血流回声的红细胞聚集机制可以解释与高剪切率动脉血流相比，低剪切率静脉血流中内部回声更明显的现象。
