Qualitative and quantitative comparison of simulated ultrasound images generated by delay-and-sum and minimum variance techniques

The beamforming technique has been successfully used for real-time ultrasound imaging and applications. Traditionally, the most commercially available ultrasound systems still implement standard Delay-and-Sum (DAS) beamforming for B-mode imaging. This technique performs the time delay and coherent summation of ultrasonic radiofrequency (RF) echoes received by individual transducer elements to align the backscattered signals at the focal point. However, the transducer aperture size and system operating frequency limit the image resolution and contrast achievable with DAS. For this reason, new methods based on adaptive beamforming algorithms, such as Minimum Variance (MV), have been studied to improve the quality of the signal received by the transducer and reduce the effects of noise and interference. This work compares a B-mode ultrasound image generated by the DAS technique and the MV combined with DAS beamforming using Field II acoustic field simulation software. A simulated phantom with 18 targets, separated into three groups, and surrounded by a uniform background, was created. For qualitative analysis, two-dimensional and three-dimensional images simulated using DAS and MV beamformers are presented. The quantitative analyses were employed to compare the performance of the MV over the DAS beamforming using axial and lateral full width at half maximum (FWHM) and geometric distortion ratio (GDR) measurements of the central target group. According to those metrics, no significant changes were observed regarding the axial FWHM. However, the MV method considerably reduced the lateral FWHM by more than 40%, with a minimum GDR of 37%.