Fast, extended velocity range flow imaging based on nonuniform sampling using adaptive wall filtering and cross correlation

Pulsed Wave Doppler (PWD) systems acquire an ensemble of N echoes per beam line at a constant pulse repetition frequency f/sub prf/. The total time span determines the velocity resolution, and f/sub prf/ the unambiguous velocity range. The ensemble size N is by approximation inversely proportional to the frame rate, assuming that the system performs interleaving. For a given frame rate, a tradeoff can only be made between velocity resolution and velocity range. We propose a pulse sequence, a velocity estimation algorithm and an adaptive wall filter for nonuniform sampling, i.e. sampling with varying sampling intervals. This approach allows to increase the frame rate by increasing the velocity estimation error for high flow velocities.