Department of Electrical Engineering, Fu Jen Catholic University, New Taipei City 24205, Taiwan.
Med Phys. 2013 Apr;40(4):042901. doi: 10.1118/1.4794493.
Measurements of the viscoelastic properties of a thrombus can be used to assess whether blood clots are likely to become occlusive or to break apart and leak into the blood circulation and block smaller vessels. An accurate method for estimating both the shear elasticity and viscosity of a blood clot in vivo is still lacking, which prompted us to use a novel shear-wave approach to measure the viscoelastic modulus of blood clots.
The shear-wave dispersion ultrasound vibrometry was used to measure both the elasticity and viscosity of blood clots. The experimental system was verified by measuring the viscoelastic modulus of phantoms containing gelatin at different concentrations. Blood-clot experiments were carried out using porcine whole blood with hematocrits ranging from 3% to 40%. The measured values for both clots and gelatin phantoms were compared to those obtained using an embedded-sphere method in order to validate the accuracy of the viscoelastic modulus estimations.
The shear elastic modulus increased from 406.9 ± 15.8 (mean ± SD) Pa for 3% gelatin to 1587.2 ± 28.9 Pa for 7% gelatin, while the viscosity increased from 0.12 ± 0.02 Pa s to 0.86 ± 0.05 Pa s, respectively. The shear modulus increased from 196.8 ± 58.4 Pa for 40%-hematocrit clots to 641.4 ± 76.3 Pa for 3%-hematocrit clots, while the viscosity increased from 0.29 ± 0.02 Pa s to 0.42 ± 0.01 Pa s, respectively.
The results from the statistical analysis indicated that both the embedded-sphere and shear-wave approaches can provide accurate estimations of the shear elasticity for clots and gelatin phantoms. In contrast, the shear-wave approach as well as other methods of rheological measurements does not provide accurate viscosity estimations for blood clots. However, the measured viscosity range of 0.29-0.42 Pa s is reasonable for blood clots.
血栓的黏弹性测量可用于评估血液凝块是否可能变得闭塞，或者是否会破裂并漏入血液循环中并阻塞较小的血管。目前仍然缺乏一种准确估计体内血液凝块剪切弹性和粘度的方法，这促使我们使用一种新的剪切波方法来测量血液凝块的黏弹性模量。
使用剪切波弥散超声振动计测量血液凝块的弹性和粘性。通过测量含有不同浓度明胶的模型的粘弹性模量来验证实验系统。使用猪全血进行凝块实验，血细胞比容范围为 3%至 40%。将测量值与嵌入球方法获得的值进行比较，以验证粘弹性模量估计的准确性。
剪切弹性模量从 3%明胶的 406.9 ± 15.8（平均值 ± 标准差）Pa 增加到 7%明胶的 1587.2 ± 28.9 Pa，而粘度分别从 0.12 ± 0.02 Pa·s 增加到 0.86 ± 0.05 Pa·s。剪切模量从 40%-血细胞比容凝块的 196.8 ± 58.4 Pa 增加到 3%-血细胞比容凝块的 641.4 ± 76.3 Pa，而粘度分别从 0.29 ± 0.02 Pa·s 增加到 0.42 ± 0.01 Pa·s。
统计分析结果表明，嵌入球法和剪切波法都可以为凝块和明胶模型提供准确的剪切弹性估计。相比之下，剪切波方法以及其他流变学测量方法不能为血液凝块提供准确的粘度估计。然而，测量得到的 0.29-0.42 Pa·s 的粘度范围对于血液凝块来说是合理的。
