Fabrication and performance of a 128-element crossed-electrode relaxor array, for a novel 3D imaging approach

Abstract

3D Ultrasound systems present several technical challenges, particularly the large number of elements in a 2D array, high electrical impedance, and image acquisition time. Crossed electrode arrays address some of these issues, especially the huge reduction in number of elements. However, creating a two-way focused 3D image in real-time is difficult with these arrays because azimuth and elevation dimensions cannot be beamformed at the same time. This typically forces one to use a synthetic aperture approach which is inherently slow and requires increased beamforming complexity over a 1D array. We have developed a new, fast and simple 3D imaging approach referred to as Simultaneous Azimuth and Fresnel Elevation (SAFE) compounding. The principle behind this technique is to perform conventional plane wave compounding with the top set of electrodes, while implementing a reconfigurable Fresnel elevation lens with the bottom electrodes. While a Fresnel lens would usually result in unacceptable secondary lobe levels, these lobes can be suppressed by compounding different Fresnel patterns. Since plane wave imaging already compounds the same slice repeatedly, the elevation Fresnel lens can be simultaneously compounded to increase the beam quality, resulting in no loss in frame rate. In this study, the design, fabrication, and characterization of a crossed electrode array based on an electrostrictive ceramic (eg. Pulse polarity depends on a DC bias) is presented.