Attenuated Vector Tomography -- An Approach to Image Flow Vector Fields with Doppler Ultrasonic Imaging
Attenuated Vector Tomography -- An Approach to Image Flow Vector Fields with Doppler Ultrasonic Imaging
复制标题
衰减矢量断层扫描——一种利用多普勒超声成像获取流矢量场的方法
DOI：
10.2172/943972
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
G. Gullberg
中科院分区：
文献类型：
--
作者：
Qiu Huang;Q. Peng;Bin Huang;A. Cheryauka;G. Gullberg
使用连续波多普勒超声获得的流量测量被表述为流矢量场的方向投影。当连续的超声波与流动的粒子碰撞时，信号就会反向散射。这个信号得到一个多普勒频移，与粒子沿超声光束的速度成正比。沿着光束的每个粒子都会发生这种情况，从而产生多普勒速度谱。光谱的第一个矩提供了沿超声光束流动的定向投影。从离探测器较远的点反射的信号的振幅将比从离探测器较近的点反射的信号的振幅低。这种效果非常类似于发射计算机断层扫描中衰减的氡变换所模拟的效果。采用最小二乘法对二维矢量场进行定向投影重建。只模拟了矢量场纵向投影的衰减投影。基于最小二乘准则，利用梯度算法重构矢量场分量。将此结果与无衰减的矢量场纵向投影重建结果进行了比较。如果衰减已知，该算法能够仅从一组方向投影测量中精确地重建全矢量more»场的两个组成部分。有衰减的流场重构效果优于无衰减的流场重构，说明衰减为流场重构提供了重要信息。这证实了之前的工作，我们表明衰减分布的知识有助于从少于所需的测量中重建MRI扩散张量场。在超声应用中，利用脉冲波透射计算机断层扫描获得衰减分布，利用连续波多普勒获得血流信息。«少
The measurement of flow obtained using continuous wave Doppler ultrasound is formulated as a directional projection of a flow vector field. When a continuous ultrasound wave bounces against a flowing particle, a signal is backscattered. This signal obtains a Doppler frequency shift proportional to the speed of the particle along the ultrasound beam. This occurs for each particle along the beam, giving rise to a Doppler velocity spectrum. The first moment of the spectrum provides the directional projection of the flow along theultrasound beam. Signals reflected from points further away from the detector will have lower amplitude than signals reflected from points closer to the detector. The effect is very much akin to that modeled by the attenuated Radon transform in emission computed tomography.A least-squares method was adopted to reconstruct a 2D vector field from directional projection measurements. Attenuated projections of only the longitudinal projections of the vector field were simulated. The components of the vector field were reconstructed using the gradient algorithm to minimize a least-squares criterion. This result was compared with the reconstruction of longitudinal projections of the vector field without attenuation. Ifattenuation is known, the algorithm was able to accurately reconstruct both components of the full vectormore » field from only one set of directional projection measurements. A better reconstruction was obtained with attenuation than without attenuation implying that attenuation provides important information for the reconstruction of flow vector fields.This confirms previous work where we showed that knowledge of the attenuation distribution helps in the reconstruction of MRI diffusion tensor fields from fewer than the required measurements. In the application of ultrasound the attenuation distribution is obtained with pulse wave transmission computed tomography and flow information is obtained with continuous wave Doppler.« less