Zhang Yufeng, Xu Lei, Chen Jianhua, Ma Huahong, Shi Xinling
Department of Electronic Engineering, Information School, Yunnan University, Kunming, Yunnan 650091, PR China.
Med Eng Phys. 2006 Jul;28(6):596-603. doi: 10.1016/j.medengphy.2005.09.002. Epub 2005 Oct 26.
The conventionally used spectral estimation technique for Doppler blood flow signal analysis is short-time Fourier transform (STFT). But this method requires stationarity of the signal during the window interval. Wavelet transform (WT), which has a flexible time-frequency window, is particularly suitable for nonstationary signals. In recently years, the WT has been used to investigate its advantages and limitations for the analysis of Doppler blood flow signals. In these studies, the estimated spectral width of Doppler blood flow signals using the WT might include significant window and nonstationarity broadening errors. These broadening errors of the time-varying spectrum were clearly undesirable since it would tend to mask the effect of flow disturbance on the spectra width. In this paper, a closed form expression for window and nonstationary root-mean-squared (rms) spectral width is given when using the WT to estimate the Doppler blood flow spectrum. The increases in the rms spectral width can be calculated and then the spectral width estimation based on the WT can be corrected.
传统上用于多普勒血流信号分析的频谱估计技术是短时傅里叶变换（STFT）。但这种方法要求信号在窗口间隔内具有平稳性。具有灵活时频窗口的小波变换（WT）特别适用于非平稳信号。近年来，小波变换已被用于研究其在分析多普勒血流信号方面的优缺点。在这些研究中，使用小波变换估计的多普勒血流信号频谱宽度可能包括显著的窗口和非平稳性展宽误差。时变频谱的这些展宽误差显然是不可取的，因为它往往会掩盖血流扰动对频谱宽度的影响。本文给出了使用小波变换估计多普勒血流频谱时窗口和非平稳均方根（rms）频谱宽度的闭式表达式。可以计算均方根频谱宽度的增加量，然后对基于小波变换的频谱宽度估计进行校正。
