Sparse Volumetric PZT Array with Density Tapering

Volumetric medical ultrasound imaging currently provides either high resolution or high frame rates. We propose a sparse array probe with only 256 elements that are density tapered. All elements are directly wired to an ultrasound engine, thus being flexible in transmission and reception. Here we present the design, realization, and characterization of a probe prototype for carotid 3D high frame rate scanning (5 MHz). The design is based on rapid prototyping with printed circuit board substrates to wire the elements to external connectors. The results show that 95% of the elements was acoustically active, producing a peak pressure of 400 kPa when focused at 24 mm with a 20 V amplitude, 3-cycle tone burst. The fractional one-way -6dB bandwidth (FBW) was 32 %, which is narrower than the designed one (50% FBW), due to an unexplained ringing effect. These results show that the probe is viable for volumetric imaging tests, albeit that it can be further optimized.