空间选择性降噪法提取血流超声多普勒信号

医学超声多普勒系统的高通滤波器在消除血管壁搏动带来的回波干扰时,也滤除了低速血流信息。为提取完整的血流超声多普勒信号,提出一种基于空间选择性降噪的方法。根据血管壁超声多普勒信号在小波尺度空间上的相关性,采用空间选择性降噪技术对管壁信号进行初步估计;然后用小波阈值滤波法消除管壁信号中残留的血流信号;最后从混合信号中减去管壁信号得到血流信号。对计算机仿真超声多普勒信号和人体颈总动脉超声多普勒信号应用本方法,实验结果表明:空间选择性降噪法能在较大的管壁/血流功率比范围内提取完整的血流信号,其平均相对误差比高通滤波器的结果降低了约45%。该方法有望成为超声多普勒系统中滤除管壁信号的一种有效方法。

Extracting Doppler ultrasound blood signals using the spatially selective noise filtration algorithm

In medical Doppler ultrasound systems, a high-pass filter is usually employed to remove wall clutter components which may also remove the information of the low velocity blood flow. To extract Doppler ultrasound blood signals exactly, a novel algorithm is proposed based on the spatially selective noise filtration. The wall signals are firstly estimated by the spatially selective noise filtration from their wavelet spatial correlation. Then the wall clutters are exactly obtained through a wavelet threshold de-noising approach which can eliminate the residual blood flow signals. Finally the intact blood flow signals are achieved by subtracting the wall clutters from the mixed signals. This algorithm has been applied to both computer simulated Doppler ultrasound signals and human carotid Doppler ultrasound signals. The experiment results show that the spatially selective noise filtration algorithm can exactly extract the blood flow signals, and achieve about 45 % lower results in the mean absolute error than that of the high-pass filtering. This algorithm is expected to be an effective method to remove the wall clutters in Doppler ultrasound systems.