Micromachined 1–3 composite dual frequency IVUS array for contrast enhanced intravascular ultasound imaging

In this paper, a dual-frequency (7 MHz/35 MHz) IVUS array for acoustic angiography was designed, fabricated and characterized. The transmit array (TX, 7 MHz) consists of eight PZT-5H 1-3 composite elements, and the receiving array (RX, 35 MHz) includes 32 elements of micromachined PMN-PT single crystal 1-3 composites. A frequency selective isolation layer was designed between transmit and receiving layers to suppress the aliasing echo effect, which allows the low-frequency transmitting wave to pass through, but the high-frequency receiving wave to be reflected at the isolation interface. The element performance was predicted by KLM model. After the TX and RX arrays were wrapped onto a φ1.2 mm needle, the characterizations were conducted. The dielectric loss and capacitance of each element were measured. The pulse-echo test of RX element showed the average center frequency of 37.2 MHz and the -6 dB fractional bandwidth of 62%. The measured crosstalk is less than -19 dB between adjacent elements. According to the hydrophone test, the TX elements were able to produce acoustic pressure > 1 MPa at 100 V excitation, which is sufficient to induce a non-linear response from microbubbles.