An Adaptive Wavelet Method for Clutter Rejection of Doppler Signal: A Simulation Study
Bioinformatics and Biomedical Engineering, (2007)Abstract
An adaptive method combining wavelet transform
(WT) with the bivariate shrinkage function (BSF) with local
variance estimation is presented for rejecting the strong clutter
from Doppler ultrasound signal. The raw Doppler signal is
decomposed by the undecimated WT in which the fast algorithm
of translation invariant discrete wavelet transform (TIDWT) is
adopted, and then the scale and wavelet coefficients selected in
terms of clutter frequency range are shrunk by BSF. The clutter
is first reconstructed by updated coefficients. This new method
was validated by simulated carotid Doppler signal, and compared
to static high pass filter (HPF). The improvements including
spectrogram and signal-to-clutter (S/C) ratio by the new method
over HPF was noticeable. For the simulated signal with S/C ratio
-20 dB, the improvement in S/C ratio was 22.66 by the new
method, but 22.05 by HPF. The mean spectrum further indicated
that the new method effectively reject clutter and simultaneously
possess nicer retention of blood components.