3D f-k migration beamformer for full matrix ultrasound imaging using row-column-addressed array

Different from conventional matrix array, row-column-addressed (RCA) array, composed of two orthogonal linear arrays with elongated elements, provides an efficient solution for three-dimensional (3D) ultrasound imaging with a small number of channels. The total focusing method (TFM) with full matrix capture (FMC) data using RCA array can realize dynamic focusing for each volumetric point in both the transmission and reception procedures, thereby producing ultrasound volumetric images with higher signal-to-noise ratio and improved resolution. However, 3D ultrasound beamforming remains computationally expensive when using the TFM with FMC data. In this study, a 3D frequency-wavenumber (f-k) migration beamformer was proposed for RCA array using FMC data. The computational cost and imaging performance of the proposed method were evaluated and compared with the conventional delay-and-sum (DAS) algorithm using point simulations, wire experiments, phantom studies, and in vivo validations. The results demonstrated that the f-k method can reduce the computational complexity from OMH²N² to OMH²log₂MH² and decrease the processing time by hundreds of times on a CPU-based MATLAB platform compared with DAS algorithm. It was also illustrated that, compared with DAS, the f-k method improved the average lateral full width at half maximum (FWHM) by 10.2% in point simulations, by 20.0% in wire experiments, and by 8.7% in wire experiments using a commercial phantom. In cyst experiments with the commercial phantom, f-k outperformed DAS in terms of contrast ratio (CR), contrast-to-noise ratio (CNR), speckle signal-to-noise ratio (sSNR), and generalized contrast-to-noise ratio (gCNR), with improvements of 28.96%, 26.45%, 11.86%, and 18.20%, respectively. In vivo validations were also conducted to evaluate the performance of the proposed method. The results demonstrate that f-k can improve imaging quality and reduce computational time for FMC 3D ultrasound imaging.