256x256 2-D array transducer with row-column addressing for 3-D imaging

In previous work we presented experimental results using a prototype 64 x 64 2-D array with row-column methods. The main benefits of this row-column design are a reduced number of interconnects, a T/R switching scheme with a simple diode circuit, and an ability to perform transmit beamforming In azimuth direction and receive beamforming in elevational direction for a volumetric imaging of targets near the transducer. In this paper, we present experimental results acquired from a new 256 x 256 2-D array transducer. The center frequency was 6.4 MHz with a -6 dill bandwidth of 57%. The series resonant impedance was 120 Ohms near 5.8 MHz. The mean crosstalk of the adjacent element was -22 dB in the frequency range of interest. For a wire target, in azimuth direction with transmit beamforming, we measured the -6 dB beamwidth to be 0.75 rum at a depth of 25.5 mm compared to a theoretical beamwidth of 0.68 mm. We successfully acquired 3-D images of a wire target and a cylindrical anechoic cyst of 10 mm in diameter made of graphite scatterers in gelatin.