Xu Tiantian, Bashford Gregory R
Department of Biological System Engineering, University of Nebraska Lincoln, Room 23, L. W. Chase Hall, Lincoln, NE 68583 USA.
Annu Int Conf IEEE Eng Med Biol Soc. 2009;2009:491-4. doi: 10.1109/IEMBS.2009.5332618.
Conventional blood flow velocity measurement using ultrasound is capable of resolving the axial component (i.e., that aligned with the ultrasound propagation direction) of the blood flow velocity vector. However, these Doppler-based methods are incapable of detecting blood flow in the direction normal to the ultrasound beam. In addition, these methods require repeated pulse-echo interrogation at the same spatial location. In this paper, we introduce a method which estimates the lateral component of blood flow within a single image frame using the observation that the speckle pattern corresponding to the blood reflectors (typically red blood cells) stretches (i.e., is "smeared") if the blood is moving in the same direction as the electronically-controlled transducer line selection in a 2D image. The situation is analogous to the observed elongation of a subject photographed with a moving camera. Here, we develop a relationship between speckle size, scan speed, and blood flow velocity. Experiments were performed with a blood flow phantom and high-frequency transducer of a commercially available ultrasound machine. Data was captured through an interface allowing access to the raw beam formed data. Blood flow with velocities ranging from 15 to 40 cm/s were investigated in this paper. Results show that there is a linear relationship between the reciprocal of the stretch factor and blood flow velocity. Two scan speeds were used in our experiments. When the scan velocity is 64.8 cm/s, compared with the theoretical model, fitting results based on experimental data gave us a linear relationship with average flow estimation error of 1.74+/-1.48 cm/s. When the scan velocity is 37.4 cm/s, the average estimation error is 0.65+/-0.45 cm/s.
使用超声进行传统的血流速度测量能够解析血流速度矢量的轴向分量（即与超声传播方向对齐的分量）。然而，这些基于多普勒的方法无法检测与超声束垂直方向的血流。此外，这些方法需要在相同空间位置重复进行脉冲回波询问。在本文中，我们介绍一种方法，该方法利用这样的观察结果来估计单个图像帧内血流的横向分量：如果血液在二维图像中与电子控制的换能器线选方向相同的方向上移动，则与血液反射体（通常是红细胞）对应的散斑图案会拉伸（即“模糊”）。这种情况类似于用移动相机拍摄的物体所观察到的伸长。在此，我们建立了散斑大小、扫描速度和血流速度之间的关系。使用商用超声设备的血流模型和高频换能器进行了实验。通过一个允许访问原始波束形成数据的接口捕获数据。本文研究了速度范围为15至40厘米/秒的血流。结果表明，拉伸因子的倒数与血流速度之间存在线性关系。我们的实验使用了两种扫描速度。当扫描速度为64.8厘米/秒时，与理论模型相比，基于实验数据的拟合结果给出了线性关系，平均血流估计误差为1.74±1.48厘米/秒。当扫描速度为37.4厘米/秒时，平均估计误差为0.65±0.45厘米/秒。
