Stacked PZT-CMUT hybrid 1D array for acoustic angiography: Preliminary results

In this work, we demonstrate the feasibility of a stacked PZT–CMUT array for acoustic angiography with separated transmit and receive bands. The system consists of a 1.9-MHz PZT-5A element bonded to a 64-element 1D CMUT array with a 6.4-MHz center frequency. CMUT’s borosilicate glass substrate serves as an acoustic matching layer for the piezoelectric transducer. Acoustic characterization was performed with a calibrated hydrophone at 22-mm depth, and in-vitro imaging was conducted using a tissue-mimicking phantom containing a 0.38-mm polyethylene tube at 22-mm depth. Microbubbles (2×10⁸ #/mL) were flowed at 120 µL/min, and received signals were high pass filtered above the third harmonic (>7.4 MHz). The PZT element generated 714 kPa peak-to-peak pressure with a mechanical index of 0.26, sufficient to induce microbubble resonance. A contrast-to-tissue ratio of 42.41 dB was achieved compared to 0.97 dB for water flow, demonstrating the potential of stacked PZT–CMUT arrays for frequency-separated acoustic angiography.