A 240 Elements Matrix Probe with Aberration Mask for 4D Carotid Artery Computational Ultrasound Imaging

Three-dimensional (3D) ultrasound provides enhanced visualization of the carotid artery (CA) anatomy and volumetric flow, offering improved accuracy for cardiovascular diagnosis and monitoring. However, fully populated matrix transducers with large apertures are complex and costly to implement. Computational ultrasound imaging (cUSi) offers a promising alternative by enabling simplified hardware design through model-based reconstruction and spatial field encoding. In this work, we present a 3D cUSi system tailored for CA imaging, consisting of a 240-element matrix probe with a 40 x 24 mm$^2$ large aperture and a spatial encoding mask. We describe the system's design, characterization, and image reconstruction. Phantom experiments show that computational reconstruction using matched filtering (MF) significantly improves volumetric image quality over delay-and-sum (DAS), with spatial encoding enhancing lateral resolution at the cost of reduced contrast ratio. LSQR-based reconstruction was demonstrated to further improve resolution and suppress artifacts. Using both Hadamard and 16-angle plane wave transmission schemes, the system achieved high-resolution images with reasonable contrast, supporting the feasibility of 4D CA imaging applications.