Detection of low velocities by a novel ultrasound multigate system

A novel ultrasound multigate system, capable of computing in real-time the FFT of Doppler signals from 64 range cells, is proven suitable for detection of low blood velocities. By imposing appropriate weighting windows to the signals that are to be Fourier transformed, possible clutter components are restricted within a few frequency bins. Filtering, where really necessary, is limited to a first-order IIR HPF. Hence, most of the information related to useful Doppler frequencies are maintained. In particular, the maximum frequency of each spectrum, which is known to be related to the maximum velocity within the corresponding sample volume, turns out to be, to a large extent, unaffected by clutter. Detection of maximum frequencies from the various sample volumes is thus proposed as a reliable means to reconstruct the true profile down to velocities proximal to zero.