Fredriksen Tonje D, Avdal Jorgen, Ekroll Ingvild K, Dahl Torbjorn, Lovstakken Lasse, Torp Hans
IEEE Trans Ultrason Ferroelectr Freq Control. 2014 Jul;61(7):1161-70. doi: 10.1109/TUFFC.2014.3015.
An important source of error in velocity measurements from conventional pulsed wave (PW) Doppler is the angle used for velocity calibration. Because there are great uncertainties and interobserver variability in the methods used for Doppler angle correction in the clinic today, it is desirable to develop new and more robust methods. In this work, we have investigated how a previously presented method, 2-D tracking Doppler, depends on the tracking angle. A signal model was further developed to include tracking along any angle, providing velocity spectra which showed good agreement with both experimental data and simulations. The full-width at half-maximum (FWHM) bandwidth and the peak value of predicted power spectra were calculated for varying tracking angles. It was shown that the spectra have lowest bandwidth and maximum power when the tracking angle is equal to the beam-to-flow angle. This may facilitate new techniques for velocity calibration, e.g., by manually adjusting the tracking angle, while observing the effect on the spectral display. An in vitro study was performed in which the Doppler angles were predicted by the minimum FWHM and the maximum power of the 2-D tracking Doppler spectra for 3 different flow angles. The estimated Doppler angles had an overall error of 0.24° ± 0.75° when using the minimum FWHM. With an in vivo example, it was demonstrated that the 2-D tracking Doppler method is suited for measurements in a patient with carotid stenosis.
传统脉冲波（PW）多普勒速度测量中一个重要的误差来源是用于速度校准的角度。由于当今临床中用于多普勒角度校正的方法存在很大的不确定性和观察者间的变异性，因此需要开发新的、更可靠的方法。在这项工作中，我们研究了先前提出的二维跟踪多普勒方法如何依赖于跟踪角度。进一步开发了一个信号模型，以包括沿任何角度的跟踪，从而提供与实验数据和模拟结果都具有良好一致性的速度谱。针对不同的跟踪角度，计算了半高宽（FWHM）带宽和预测功率谱的峰值。结果表明，当跟踪角度等于波束与血流角度时，谱具有最低的带宽和最大功率。这可能有助于开发新的速度校准技术，例如通过手动调整跟踪角度，同时观察对频谱显示的影响。进行了一项体外研究，其中通过二维跟踪多普勒频谱的最小FWHM和最大功率预测了3种不同血流角度下的多普勒角度。使用最小FWHM时，估计的多普勒角度总体误差为0.24°±0.75°。通过一个体内实例，证明了二维跟踪多普勒方法适用于颈动脉狭窄患者的测量。
