Impact of spacing of ultrasound receiving beams on estimation of 2D motion velocity

For more detailed measurement of cardiovascular motion and complex blood flow, a two-dimensional (2D) velocity estimation method is required in functional ultrasound imaging. The block matching method based on the correlation function is one of the standard 2D motion estimators. In this study, we investigated the effect of lateral sampling intervals of an ultrasonic B-mode image on the accuracy in velocity estimation. In simulation, bias error (BE) in estimated velocities became -13% with an ultrasonic center frequency of 7.5 MHz and spacings of receiving beams of 0.2 mm. Such a BE was improved from -13% to -1.4% by changing the spacings from 0.2 to 0.1 mm. In the in vivo experiment, the maximum velocity obtained with spacings of 0.2 mm was underestimated by -16% as compared to those obtained with 0.1 mm. Hence, the trend was similar to that in the simulation.