Row-Multiplexed 1,024 Element Large Aperture Array for Electronic Scanning in Elevation

Abstract

We have been developing highly-integrated and modular large aperture multi-row 1.75D linear arrays interfaced to a configurable ultrasound system (Verasonics Vantage 32LE) using custom ASIC multiplexing electronics with the goal to improve detection of liver cancer deep in the body. The array consists of multiple rows which are capable of multiplexing an aperture in elevation for realization of synthetic focusing and imaging in both azimuthal and elevational planes. The large array addresses 1,024 acoustic elements $(\boldsymbol{42}\ \mathbf{mm} \times \boldsymbol{16}\ \mathbf{mm}$ aperture with $\boldsymbol{650}\mu \mathbf{m}\ \mathbf{azi}. \times \boldsymbol{1000\ \mu} \mathbf{m}$ elev. element pitch) with 64 elements in azimuth and 16 rows in elevation. Each of the columns are interfaced directly to a single respective imaging system channel. Rows are selected using commands sent to a local FPGA which controls the ASICs during imaging. Beamforming for individual rows in azimuth is accomplished by the configurable imaging system using plane wave imaging in azimuth and either SRA or STRA synthetic aperture imaging performed to create images in the elevation dimension. Imaging in elevation was performed at Fc $\boldsymbol{=2.5}$ MHz and achieved 1.3 mm and 0.8 mm resolution at a depth of 20 mm for SRA and STRA modes respectively. We are currently integrating the probe acoustic array and electronics into a handheld form factor for future use in human imaging.