Synthetic aperture 3D ultrasound imaging schemes with S-sequence bias-encoded top-orthogonal-to-bottom-electrode 2D CMUT arrays

Crossed electrode arrays, wherein electrodes are connected in individually addressable rows and columns, have been previously investigated as a means to reduce the number of channels in two-dimensional ultrasound arrays for three-dimensional imaging. Previously envisioned imaging schemes have been limited in their resolution and focusing ability due to their inability to perform active focusing in both the lateral and elevational direction for both transmit and receive. As well, signal-to-noise ratio (SNR) can be compromised when transmitting or receiving on only one row or column at a time. A new imaging method is proposed for this array architecture using capacitive micromachined ultrasound transducers (CMUTs) which can provide two-way focusing in both lateral and elevational directions while providing optimal SNR. This method is a variation of synthetic aperture imaging wherein the columns active upon transmit and receive events are determined by applying a bias to specific columns upon transmission and reception in an S-sequence encoded pattern. Mathematical derivations of this method are presented and simulations are done to compare this imaging method to previously published crossed-electrode array imaging schemes, as well as to fully-populated 2-D phased array imaging.