Spectral Doppler flow velocity and Doppler angle estimations for small vessel by large sample volume

In this paper, we present a Doppler angle and flow velocity estimation method for small vessels by using a large sample volume length. We use the mode frequency, f_d, and the -3 dB maximum frequency, to calculate the Doppler angle and flow velocity while keeping the sample volume length larger than the beam path length across the blood vessel. We have successfully implemented this approach in a clinical ultrasound system for measuring a constant and pulsatile flow generated by a UHDC flow phantom in a 4 mm polyethylene tube between 50° and 80° Doppler angle. The standard deviation of the estimated flow velocity is 3.4 cm/s (about 11%) for a constant flow with 23.8 cm/s flow velocity, and is 6 cm/s (about 15%) for a pulsatile flow with 35.8 cm/s peak flow velocity