Handheld Large 2D Array with Azimuthal Planewave and Row-Multiplexed Elevation Beamforming Enabled by local ASIC Electronics.

Large aperture 2D arrays benefit from improved lateral resolution at depth, due to the dependence of beamwidth on the inverse of the aperture width, and improved contrast resolution due to electronic focusing. We have been developing modular large aperture multi-row 1,024 (64 azimuth × 16 elevation) element, 2D arrays based on custom-designed and locally integrated Application Specific Integrated Circuit (ASIC) multiplexing devices. The implemented handheld large array prototype probe for human imaging consists of multiple rows with multiplexed synthetic aperture in elevation and planewave transmits in azimuth. The pitch of the acoustic array is 650 μm in azimuth by 1,000 μm in elevation, with a 2.4 MHz (FBW=88%) center frequency and total active aperture of 42 mm × 16 mm. We interfaced the large aperture array and multiplexing ASICs, along with local preamplifier devices for improved sensitivity, and a local FPGA for digital ASIC control, to a configurable ultrasound imaging platform and demonstrate 2D orthogonal and full 3D-beamformed imaging. The implemented imaging prototype includes local buffering for improved sensitivity of the high impedance 2D array elements, and realizes penetration down to 140 mm, experimental lateral/axial resolution at 67 mm of 1.1 mm/0.4 mm, and maximum experimental CNR of 2.1 for 8 mm cylindrical cysts, and 1.7 for 10 mm spherical cysts. We demonstrate in-vivo imaging of liver in human volunteers utilizing a hermetically-sealed and safety-validated handheld prototype of the large 2D array. Preliminary results are promising for clinical imaging in future studies.