IEEE Trans Ultrason Ferroelectr Freq Control. 2013 Oct;60(10):2079-88. doi: 10.1109/TUFFC.2013.2798.
The signal backscattered by blood cells crossing a sample volume produces a Doppler power spectrum determined by the scatterers¿ velocity distribution. Because of intrinsic spectral broadening, the peak Doppler frequency observed does not correspond to the peak velocity in the flow. Several methods have been proposed for estimating the maximum velocity component--an important clinical parameter--but these methods are approximate, based on heuristic thresholds that can be inaccurate and strongly affected by noise. Reported here is a method of modeling the Doppler power spectrum of a flow, and from that model, determining what Doppler frequency on the descending slope of the power spectrum corresponds to the peak velocity in the insonated flow. It is shown that, for a fully insonated flow with a parabolic velocity distribution, the peak velocity corresponds to the Doppler frequency at the half-power point on that slope. The method is demonstrated to be robust with regard to the effects of noise and valid for a wide range of acquisition parameters. Experimental maximum velocity measurements on steady flows with rates between 100 and 300 mL/min (peak velocity range 6.6 cm/s to 19.9 cm/s) show a mean bias error that is smaller than 1%.
血细胞穿过样品体积所产生的背向散射信号产生一个由散射体速度分布决定的多普勒功率谱。由于固有频谱展宽，所观察到的峰值多普勒频率与流场中的峰值速度不对应。已经提出了几种估计最大速度分量（一个重要的临床参数）的方法，但这些方法是近似的，基于启发式阈值，这些阈值可能不准确，并受到噪声的强烈影响。本文报告了一种对流动的多普勒功率谱进行建模的方法，并从该模型中确定功率谱下降斜率上的哪个多普勒频率对应于被照射流场中的峰值速度。结果表明，对于具有抛物线速度分布的完全照射流，峰值速度对应于该斜率上半功率点的多普勒频率。该方法对于噪声的影响具有鲁棒性，并且适用于广泛的采集参数。对速率在 100 到 300 毫升/分钟之间（峰值速度范围为 6.6 厘米/秒至 19.9 厘米/秒）的稳态流进行的最大速度实验测量显示，平均偏差误差小于 1%。
