Department of Electrical Engineering, Fu Jen Catholic University, Hsin Chuang District, Taipei, Taiwan.
Ultrasound Med Biol. 2011 Oct;37(10):1722-33. doi: 10.1016/j.ultrasmedbio.2011.06.026. Epub 2011 Aug 6.
The viscoelastic properties of thrombus play a significant role when the clot closes a leak in a vessel of the blood circulation. The common method used to measure the viscoelastic properties of a clot employs a rheometer but this might be unsuitable due to the clot fiber network being broken up by excessive deformation. This study assessed the feasibility of using a novel acoustic method to assess the viscoelastic properties of blood clots. This method is based on monitoring the motion of a solid sphere in a blood clot induced by an applied instantaneous force. Experiments were performed in which a solid sphere was displaced by a 1 MHz single-element focused transducer, with a 20 MHz single-element focused transducer used to track this displacement. The spatiotemporal behavior of the sphere displacement was used to determine the viscoelastic properties of the clot. The experimental system was calibrated by measuring the viscoelastic modulus of gelatin using different types of solid spheres embedded in the phantoms and, then, the shear modulus and viscosity of porcine blood clots with hematocrits of 0% (plasma), 20% and 40% were assessed. The viscoelastic modulus of each clot sample was also measured directly by a rheometer for comparison. The results showed that the shear modulus increased from 173 ± 52 (mean ± SD) Pa for 40%-hematocrit blood clots to 619.5 ± 80.5 Pa for plasma blood clots, while the viscosity decreased from 0.32 ± 0.07 Pa∙s to 0.16 ± 0.06 Pa∙s, respectively, which indicated that the concentration of red blood cells and the amount of fibrinogen are the main determinants of the clot viscoelastic properties.
血栓的黏弹性特性在血栓封闭血液循环中血管的漏口时起着重要作用。常用的测量血栓黏弹性特性的方法是使用流变仪，但由于血栓纤维网络因过度变形而被破坏，这种方法可能并不适用。本研究评估了使用新型声学方法评估血液凝块黏弹性特性的可行性。该方法基于监测施加瞬时力后血栓中固体球的运动。实验中，使用 1 MHz 单元件聚焦换能器使固体球发生位移，并用 20 MHz 单元件聚焦换能器跟踪此位移。通过球位移的时空行为来确定血栓的黏弹性特性。通过在不同类型的固体球嵌入的体模中测量明胶的黏弹性模量来校准实验系统，然后评估红细胞比容分别为 0%（血浆）、20%和 40%的猪血凝块的剪切模量和黏度。还使用流变仪直接测量每个凝块样本的黏弹性模量进行比较。结果表明，红细胞比容为 40%的血凝块的剪切模量从 173 ± 52（均值 ± 标准差）Pa 增加到血浆血凝块的 619.5 ± 80.5 Pa，而黏度从 0.32 ± 0.07 Pa∙s 降低到 0.16 ± 0.06 Pa∙s，这表明红细胞浓度和纤维蛋白原含量是凝块黏弹性特性的主要决定因素。
