Synthetic transmit beams with multi-line and diverging wave transmission for real-time, high frame rate, low-artefact tissue Doppler imaging

The use of wide beams in transmission and parallel beamforming in reception allows increasing the frame rate of ultrasound images. Any misalignment between the transmitted beams and the received lines determines spatial discontinuities that appear as strip-like imaging artifacts. The use of synthetic transmit beams (STB) has been shown effective to reduce these artifacts, although with an increased computational burden that might compromise its real-time implementation. This paper shows how STB was implemented on the ULA-OP 256 research scanner in combination with both multiline and diverging wave transmissions. The system performance is demonstrated in cardiac tissue Doppler imaging applications, showing that strip-like artifacts can be attenuated and, at the same time, real-time B-mode images can be obtained at a rate of 688 frames/s, which is high enough to process tissue Doppler images up to 230 frame/s, depending on the ensemble length.