Forward-looking 30-MHz phased-array transducer for peripheral intravascular imaging

This paper describes the design, fabrication, and testing of a forward-looking 30-MHz phased-array transducer for peripheral intravascular imaging. The array features 32 piezoelectric elements arranged in a linear 2-2 composite configuration dry etched into a piece of PMN-30%PT single crystal and separated by non-conductive epoxy kerfs at a 25-μm pitch, yielding a total active aperture of 0.8 mm in the azimuth direction and 1.0 mm in the elevation direction, with an elevation natural focal depth of 5.0 mm. The array includes non-conductive epoxy backing and two front matching layers. A custom flexible circuit connects the array piezoelectric elements to a bundle of 32 individual 48-AWG micro-coaxial cables enclosed within a 0.6-m long 8 F catheter. Performance characterization was evaluated via finite element analysis simulations and afterwards compared to measured results, which showed an average center frequency of 28.9 MHz, an average bandwidth of 36.4% at -6 dB, and crosstalk less than -26.5 dB. Imaging of a tungsten fine-wire phantom resulted in axial and lateral spatial resolutions of approximately 65 μm and 215 μm, respectively. The imaging capability was further evaluated with a porcine carotid artery phantom, demonstrating the suitability of the proposed phased-array transducer for peripheral intravascular imaging.