Time Domain Formulation of Pulse-Doppler Ultrasound and Blood Velocity Estimation by Cross Correlation
Time Domain Formulation of Pulse-Doppler Ultrasound and Blood Velocity Estimation by Cross Correlation
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DOI：
10.1177/016173468600800201
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发表时间：
1986-04
影响因子：
2.3
通讯作者：
O. Bonnefous;P. Pesque
中科院分区：
文献类型：
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作者：
O. Bonnefous;P. Pesque
多普勒效应通常被描述为来自运动目标的后向散射信号相对于发射频率的频移。最近，由于开发了一种基于连续回波相移测量的新型速度估计器，实时血流成像已经成为可能。然而，这种方法受到众所周知的脉冲多普勒仪器的限制。本文提出了一种新的脉冲多普勒效应公式，将运动目标云连续回波的脉冲多普勒效应描述为由于散射体在两个激励之间的位移而引起的时间上的递进平移。这种方法使我们能够有效地生成计算机模拟数据，以便准确地评估各种处理技术。此外，它还导致了一种新的时域速度估计器，用于测量与局部血流速度成比例的时移。其中，接收到的射频信号相互关系很好。首先从连续的距离门控回波对计算局部互相关函数，然后通过搜索具有最大相关性的时间位置来确定时移。用宽频带换能器，时间相关技术可以提供精确的速度剖面。此外，克服了传统的脉冲多普勒速度限制，因为在测量时移而不是相移时没有歧义。这些主要优点应该使定量流映射成为可能，并且更加可靠。
The Doppler effect is usually described as a frequency shift of the backscattered signals from moving targets with respect to the frequency transmitted. Recently, real-time blood flow imaging has become possible thanks to the development of a new velocity estimator based on phase-shift measurements of successive echoes. However, this method suffers from the well-known limitations of pulse-Doppler instruments. A new formulation is presented which describes the pulse-Doppler effect on the successive echoes from a cloud of moving targets as a progressive translation in time due to the displacement of the scatterers between two excitations. This approach allows us to generate efficiently computer-simulated data in order to evaluate accurately the various processing techniques. Furthermore, it leads to a novel class of velocity estimators in the time domain which measure the time shifts which are proportional to the local blood velocity. Among them, the cross correlation of the received rf signals turns out to be well suited. A local cross-correlation function is first calculated from a consecutive pair of range-gated echoes and the time shift is then determined by searching for the time position with the maximum correlation. The time-correlation technique is shown to provide accurate velocity profiles with broadband transducers. Moreover, the classical velocity limitation of pulse-Doppler is overcome because there is no ambiguity in measuring a time shift instead of a phase shift. These major advantages should make quantitative flow mapping possible and more reliable.