pulsed Doppler techniques used in Colour Flow Mapping such as spectral Doppler
or autocorrelation are
monochromatic, focused on the analysis of the centre transmit frequency. As such all the algorithms using those approaches are
limited: in terms of spatial Doppler resolution because of the long pulses
typically used for transmission, in terms of frame rate because of the
necessity to perform many Doppler lines repetitions and additional B-mode
imaging transmissions, and in terms of accuracy which depends on the stability
of the Doppler signal at the frequency considered. A velocimetry technique is presented which estimates
the shifts between successive Doppler line segments using the phase information
provided by the Fourier transform. Such an approach allows extraction of more
information from the backscattered signal through the averaging of results from
multiple frequencies inside the bandwidth, as well as the transmission of wide
band-high resolution-pulses. The technique
is tested on Doppler signals acquired with a research scanner in a straight
latex pipe perfused with water and cellulose scatterers, and on an ultrasound
contrast agent solution. The results are compared with the velocity estimates
provided by standard spectral Doppler and autocorrelation methods. Results show
that the proposed technique performs better than both other approaches, especially
when few Doppler lines are processed. The technique is also shown to be
compatible with contrast Doppler imaging. The proposed approach enables high
frame rate, high resolution Doppler.
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