3D Large-Scale Subwavelength-Resolution Sound Sheet Tomography Based on an Active and Programmable Circular Meta-Array.

Tomography enables volumetric visualization of internal structures with high fidelity, which has transformed diverse fields of science and engineering. Ultrasound tomography, in particular, provides radiation-free, real-time, and low-cost imaging. Conventional linear and planar array designs typically impose inherent limits on aperture, coverage, and resolution, hindering accurate imaging of deep structures. Here, we present an active and programmable circular meta-array of 2048 channels integrated with cylindrical acoustic lenses, generating a wide-angle point-source radiation in plane and a thin flat sound-sheet beam out of plane. This configuration delivers omnidirectional homogeneous coverage and dynamic focusing, allowing comprehensive full-matrix echo acquisition. Based on the circular meta-array, subwavelength resolution ultrasonic images (∼0.8λ) are obtained with delay multiply and sum reconstruction. Extending to the volumetric tomography, the acoustic system reconstructs complex 3D objects and resolves human soft tissues and musculoskeletal structures. Our work provides a versatile platform for ultrasound tomography and opens an avenue for various advanced applications in biomedical imaging and therapeutic monitoring.