Search

The coil separation of phased-array coils is an important issue if a wide area of interest is to be imaged. An equivalent circuit of two circular-shaped coils was used to compute the optimal distance in a two phased-array coil. This circuit included the mutual inductance of two circular coils. An expression for the mutual inductance was derived and the resulting values included in the circuit. With all these elements an equivalent circuit of two overlapped circular coils was built to simulate a phased-array coil. To find a solution to this circuit, specifically written programmes in Spice Opus Light were used. Optimal separations were calculated from separation-vs-attenuation for different coil radii. Results compare very well with those reported in the literature.

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.