Fabrication and Characterization of a Miniaturized 15-MHz Side-Looking Phased-Array Transducer Catheter

This paper describes the development of a miniaturized 15-MHz side-looking phased-array transducer catheter. The array features a 2-2 linear composite with 64 piezoelectric elements mechanically diced into a piece of PMN-30% PT single crystal and separated by nonconductive epoxy kerfs at a 50-μm pitch, yielding a total active aperture of 3.2 mm in the azimuth direction and 1.8 mm in the elevation direction, with an elevation natural focal depth of 8.1 mm. The array includes nonconductive epoxy backing and two front matching layers. A custom flexible circuit connects the array piezoelectric elements to a bundle of 64 individual 48-AWG microcoaxial cables enclosed within a 1.5-m-long 10F catheter. Performance characterization was evaluated via finite-element analysis simulations and afterward compared against obtained measurement results, which showed an average center frequency of 17.7 MHz, an average bandwidth of 52.2% at -6 dB, and crosstalk less than -30 dB. The imaging of a tungsten finewire phantom resulted in axial and lateral spatial resolutions of approximately 90 and 420 μm, respectively. The imaging capability was further evaluated with colorectal tissue-mimicking phantoms, demonstrating the potential suitability of the proposed phased-array transducer for the intraoperative assessment of surgical margins during minimally invasive colorectal surgery procedures.