Rectilinear 3-D ultrasound imaging using synthetic aperture techniques

In our continuing efforts to improve 3D rectilinear ultrasound, we present a new design using a simplified interconnect architecture, switching scheme, and synthetic aperture methods. The main benefit of this design is the interconnect, where an expensive multilayer flex circuit is no longer required. The interconnect uses a row-column addressing scheme to enable different groups of elements. Over multiple transmissions, this design is capable of essentially synthesizing a 256 × 256 = 65536-element, fully sampled 2D rectilinear array. Using a sparse synthetic transmit aperture, a column or several columns of elements are bussed together, so that a cylindrical wavefront is emitted into the field. In receive, the echoes from individual elements along a row are recorded by the system receive channels. Different columns and rows are selected in subsequent transmissions, and the echoes from these transmit events are then recorded to synthesize a fully sampled array. We have performed computer simulations of a 10 MHz, 256 × 256 2D synthetic array subaperture to determine the radiation pattern. For an F/2 aperture, the on-axis case (x,y,z) = (0,0,20) mm showed a narrow beam down to -52 dB. In the azimuth direction, on-axis lateral beamwidths at -6, -20, and -40 dB were 0.21 mm, 0.43 mm, and 0.87 mm, respectively. As a tradeoff, elevational on-axis beamwidths were wider, respectively 0.18 mm, 1.17 mm, and 7.82 mm for the same corresponding dB levels.