Parallel- and micro-beamforming challenges in real-time, high-frame-rate, ultrasound imaging

Delay-and-sum beamforming for classic (line-by-line) ultrasound imaging is usually performed in real-time by FPGAs and GPUs. However, when a high-frame-rate (HFR) has to be achieved, beamforming becomes challenging. Here, the echoes following the transmission of multi-line focused beams, plane waves, or diverging waves, must be simultaneously beamformed along multiple view lines. Such parallel beamforming is feasible online when the scanner is endowed with high flexibility and processing power. This talk will show how the FPGAs of the ULA-OP 256, a hardware-based open scanner, were efficiently utilized to enable parallel beamforming at high speed. The talk will also discuss how the data transfer between the scanner boards impacts the frame rate, which actually achieved 4400 frames per second through a new communication topology. The talk will also examine the image quality deterioration emerging when HFR imaging sequences are implemented in probes equipped with a microbeamformer (uB) that was designed for focused beam transmission. Simulations show how the transmitted beamwidth and uB size impact the image contrast and resolution, taking into account that the uB ASIC cannot handle multiple sets of delays and apodization weights after each transmit event. Technological improvements needed in the next generation uBs will be finally discussed.