Adaptive Rejection of Nonstationary Clutter in Ultrasonic Color Flow Imaging

For accurate biomedical ultrasound blood flow measurement, it is important to suppress the clutter signals originated from stationary and slowly moving tissue sufficiently. Without sufficient clutter rejection, low velocity blood flow can´t be measured, and estimates of higher velocities will have a large bias. Traditional clutter rejection methods such as FIR, IIR, regression filters and down mixing with the mean frequency of the clutter signal are based on the hypothesis that the clutter signal originates from stationary or moving tissue with a constant velocity. While in realistic ultrasonic imaging, there exists considerable acceleration of tissue motion because of pulsation, breathing and movement of the transducer, therefore, the clutter signal is a non-stationary stochastic process. Under this condition, traditional clutter rejection filters will bring large bias to the flow velocity estimation. In this paper, we propose a new clutter filter adapted to accelerated tissue motion. Simulation results show that non-stationary clutter signals can be efficiently attenuated using this clutter filter, especially for low blood flow velocity and high amplitude clutter conditions