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Abstract：
Ultrasound speckle image of blood is mainly attributed by red blood cells (RBCs) which tend to form RBC aggregates. RBC aggregates are separated into individual cells when the shear force is over a certain value. The dissociation of RBC aggregates has an influence on the performance of ultrasound speckle image velocimetry (SIV) technique in which a cross-correlation algorithm is applied to the speckle images to get the velocity field information. The present study aims to investigate the effect of the dissociation of RBC aggregates on the estimation quality of SIV technique. Ultrasound B-mode images were captured from the porcine blood circulating in a mock-up flow loop with varying flow rate. To verify the measurement performance of SIV technique, the centerline velocity measured by the SIV technique was compared with that measured by Doppler spectrograms. The dissociation of RBC aggregates was estimated by using decorrelation of speckle patterns in which the subsequent window was shifted as much as the speckle displacement to compensate decorrelation caused by in-plane loss of speckle patterns. The decorrelation of speckles is considerably increased according to shear rate. Its variations are different along the radial direction. Because the dissociation of RBC aggregates changes ultrasound speckles, the estimation quality of SIV technique is significantly correlated with the decorrelation of speckles. This degradation of measurement quality may be improved by increasing the data acquisition rate. This study would be useful for simultaneous measurement of hemodynamic and hemorheological information of blood flows using only speckle images.
摘要：
血液的超声斑点图像主要归因于倾向于形成RBC聚集体的红细胞(RBC)。当剪切力超过一定值时,RBC聚集体被分离成单个细胞。红细胞聚集体的解离对超声散斑图像测速（SIV）技术的性能有影响，在该技术中，将互相关算法应用于散斑图像以获得速度场信息。本研究旨在探讨红细胞聚集体解离对SIV技术估计质量的影响。从具有变化的流速的模拟流动回路中循环的猪血液捕获超声B模式图像。为了验证SIV技术的测量性能，通过SIV技术测量的中心线速度与通过多普勒频谱图测量的中心线速度进行了比较。通过使用散斑图案的去相关来估计RBC聚集体的解离，其中后续窗口的偏移与散斑位移一样多，以补偿由散斑图案的面内损失引起的去相关。斑点的去相关根据剪切速率而大大增加。其变化沿径向方向是不同的。因为红细胞聚集体的解离改变了超声斑点，SIV技术的估计质量与斑点的去相关显着相关。可以通过增加数据采集速率来改善测量质量的这种下降。这项研究对于仅使用斑点图像同时测量血流的血液动力学和血液流变学信息非常有用。
