Velocity and acceleration estimation employing nonuniform sampling

Our group has previously proposed nonuniform sampling for flow velocity estimation. Standard pulsed wave Doppler (PWD) systems acquire an ensemble of N echoes per beam line at a constant pulse repetition frequency f_prf. The total time span determines the velocity resolution, and f_prf the unambiguous velocity range. The ensemble size N is by approximation inversely proportional to the frame rate, assuming that the system performs interleaving. If sampling intervals are chosen nonuniformely, the total time span can be increased, while keeping N and the shortest sampling interval constant. In this example velocity range and frame rate are unchanged, and measurement accuracy for low flow velocities is gained at the expense of measurement accuracy for high flow velocities. The extended time span makes the flow estimation susceptible to effects of acceleration and decorrelation. Thus, we have refined the flow estimation algorithms by taking into account both effects.