Real-time rectilinear 3-D ultrasound with 4:1 receive mode multiplexing

In previous work, we developed two generations of a real-time rectilinear volumetric scanner operating at 5 MHz for abdominal, breast or vascular imaging using Mills cross 2-D array and rectilinear periodic 2-D array. To improve spatial resolution performance and sensitivity, we developed a new design using 4:1 receive mode multiplexing. With 4:1 multiplexing, the new 2-D array of 65,000 elements has 4 × 256 = 1024 receivers so that 256 receivers can be used on any image line. The two major benefits of using receive mode multiplexing include: (1) an increase in receive sensitivity due to the greater number of receive elements; and (2) an increase in receive element density which reduces grating lobe and clutter levels. Theoretical simulations and analysis show an increase of about 13 dB in sensitivity compared to our previous work. With these encouraging results, a new 65,000 element 5 MHz 2-D array having 1024 receivers and 169 transmitters was prototyped. In addition, multiplexer and control circuitry were designed, built, and interfaced with both the transducer and volumetric scanner. Images of tissue-mimicking phantoms and in vivo were obtained. Using a spherical cyst phantom, experimental results showed a +12 dB improvement in signal-to-noise ratio and a +6 dB improvement in contrast compared to our previous work.