Time-frequency distribution applied to blood flow velocity profiles

The Fourier analysis has become a standard tool to study blood flow in cardiovascular system. However it is not able to perform a time-frequency analysis of signals generated by the blood flow. Non-stationary signals, such as Doppler signals, require the notion of frequency analysis that is local in time. Time-frequency distributions can be applied to perform time-frequency analysis. The aim of this work is to reconstruct the blood flow profiles using Cohen´s class time-frequency distribution by estimating the instantaneous frequency of a simulated pulsed Doppler signal. Velocity profiles were theoretically computed from Womersley´s equation for a pulsatile stationary-state flow in a circular-cross section tube. Errors in the estimation of the pseudo-instantaneous mean frequency were computed for different sampling windows sizes. The blood flow velocity profiles of a carotid artery calculated with the Wigner-Ville time-frequency distribution show a good agreement with the velocity profiles given by the Womersley´s model.