Effects from correction of speed of sound in transmit and receive beamforming using focus beam

In this study, focusing methods were investigated for generation of an ultrasonic beam with a uniform lateral width across the axial imaging field of view through numerical simulation using Field II. Also, the influence of the mismatch between the speed of sound (SoS) assumed in beamforming process and actual one was evaluated by wire and cyst phantom experiments. In the simulation, conventional, hybrid, and non-cylindrical focusing methods were evaluated based on the evaluation metrics, i.e. depth of field and lateral beam width. For the three focusing methods, the proper imaging parameters were determined based on the simulation results. In the phantom experiments, the lateral resolution was improved by correcting the SoS in receive beamforming. Additionally, the correction of the SoS in transmission focusing improved the uniformity of beam width and image contrast.