Frequency-wavenumber migration for orthogonal plane wave imaging using row-column-addressed arrays

Row-column-addressed (RCA) arrays, composed of two orthogonal linear arrays with elongated elements, enable three-dimensional (3D) imaging with a larger aperture and fewer channels than conventional matrix arrays. Orthogonal plane-wave (OPW) coherent compounding is a specialized insonation mode for RCA arrays, characterized by the emission of orthogonally tilted plane waves and the coherent compounding of echo data to generate 3D images. Nevertheless, 3D beamforming is computationally expensive when using the conventional delay-and-sum algorithm. Frequency-wavenumber (F-K) beamformers are highly efficient beamforming solutions and have been widely investigated for two-dimensional (2D) imaging using linear arrays and for 3D imaging with matrix arrays. In contrast, the F-K beamformer for RCA-based OPW imaging remains to be further developed. In this work, an F-K domain beamforming strategy (OPW f-k) is proposed for efficient volumetric image reconstruction in RCA-based OPW imaging. The proposed method achieves a computational complexity of O(PMH^2 \log_2(MH)) compared to O(PNMH^2) required by the conventional delay-and-sum algorithm, resulting in an 11-fold processing time reduction on a CPU-based MATLAB platform. Besides, simulation and phantom experimental results indicate that OPW f-k can improve imaging quality, with quantitative evaluations demonstrating enhanced spatial resolution (2.19% reduction in full width at half maximum), contrast ratio (12.96% increase), and contrast-to-noise ratio (17.84% increase) compared to OPW DAS. In vivo carotid artery imaging further confirms the clinical viability of the method for volumetric imaging. These results suggest that the proposed F-K method is a promising solution for RCA-based 3D OPW imaging.