This paper describes the design and fabrication of a miniature ultrasonic phased array transducer used for intervention guidance. Currently ultrasound probes are often placed at the body surface of the patients, leading to several drawbacks including the limitation of penetration and image quality. In order to improve the reliability of the guiding process, we propose a miniature phased array transducer that can be placed adjacent to the intervention device during the interventional procedure. In this paper, we report the work that has been carried out on the development of this miniature phased array transducer. It comprised 48 elements housed in a 3-mm-diameter needle. A specially designed flexible circuit was used in accommodating the transducer array in the long, thin needle housing. The center frequency and the fractional bandwidth were approximately 20 MHz and 42% respectively, with an average crosstalk lower than −30 dB. The axial and azimuth resolutions were approximately 80 µm and 210 µm respectively. The imaging capability of the transducer was further evaluated by acquiring the B-mode images of a needle in a cow liver. The performance of the proposed phased array transducer demonstrates the feasibility of such an approach for interventional guidance.

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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. Index Terms-High-frequency imaging, materials/technology for medical transducers, piezoelectric and ferroelectric transducer materials, transducer modeling [finite-element analysis (FEA) and analytical].

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This paper describes the development of a miniaturized high frequency linear array that can be integrated within a core biopsy needle to improve tissue sampling accuracy during breast cancer biopsy procedures. The 64 element linear array has an element width of 14 μm, kerf width of 6 μm, element length of 1 mm and element thickness of 24 μm. The 2–2 array composite was fabricated using deep reactive ion etching of PMN-PT single crystal material. The array composite fabrication process as well as a novel high density electrical interconnect solution are presented and discussed. Array performance measurements show that the array had a center frequency and fractional bandwidth (−6 dB) of 59.1 MHz and 29.4%, respectively. Insertion loss and adjacent element cross talk at the center frequency were −41.0 dB and −23.7 dB, respectively. A B-mode image of a tungsten wire target phantom was captured using a synthetic aperture imaging system and the imaging test results demonstrate axial and lateral resolutions of 33.2 μm and 115.6 um, respectively.