Title :
Noise reduction in directional signals using multiple Morse wavelets illustrated on quadrature Doppler ultrasound
Author :
Olhede, Sofia C. ; Walden, Andrew T.
Author_Institution :
Dept. of Math., Imperial Coll. of Sci., Technol. & Med., London, UK
Abstract :
The use of multiple complex-valued Morse wavelets for the scalogram study of signals which are unidirectional at any time, but are bidirectional overall is considered. These wavelets are well-suited to identifying the forward and reverse components. Scalogram averaging which is possible due to the multiplicity of the complex-valued wavelets leads to a scalogram with reduced noise. Information from positive and negative scales can then be used to estimate a final "cleaned" scalogram. Quadrature Doppler ultrasound blood flow in the femoral artery is taken as an example to clearly illustrate the noise reduction.
Keywords :
Doppler measurement; biomedical ultrasonics; blood flow measurement; medical signal processing; patient diagnosis; signal denoising; wavelet transforms; bidirectional signals; blood flow; directional signals; femoral artery; multiple Morse wavelets; negative scales; noise reduction; positive scales; quadrature Doppler ultrasound; scalogram averaging; time-scale analysis; unidirectional signals; Arteries; Blood flow; Continuous wavelet transforms; Discrete wavelet transforms; Frequency estimation; Mathematics; Noise reduction; Ultrasonic imaging; Wavelet analysis; Wavelet transforms; Blood Flow Velocity; Computer Simulation; Echocardiography, Doppler; Femoral Artery; Humans; Models, Cardiovascular; Quality Control; Reproducibility of Results; Sensitivity and Specificity; Signal Processing, Computer-Assisted; Stochastic Processes;
Journal_Title :
Biomedical Engineering, IEEE Transactions on
DOI :
10.1109/TBME.2002.807322
