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

Abstract

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].

Phased-Array Transducer for Intracardiac Echocardiography Based on 1–3 Piezocomposite

“…For the transducer, the measurement of − 6 dB directivity was ± 30 • , as shown in Figure 11, which can serve satisfactorily in the performance of phased-array beam. Similar results were reported with directivity of approximately ±25 • for a 2-2 composite phased array (Bezanson et al, 2014;Cabrera-Munoz et al, 2019).…”

“…Currently, many researchers have focused their efforts on the development of miniaturized phased-array transducer (Bezanson et al, 2014;Chiu et al, 2014;Basij et al, 2019;Cabrera-Munoz et al, 2019). The current manufacturing process of the transducer is rather cumbersome.…”

“…The current manufacturing process of the transducer is rather cumbersome. For example, sputtering Au/Cr layer needs to be performed multiple times to connect the ground of array elements (Cannata et al, 2006), and individual element electrodes are separated by removing the gold layer by using photolithography or Cr/Au etching and carefully aligned with the electrode patterns on the flexible circuit (Chen et al, 2014;Chiu et al, 2014), using conductive epoxy to bond the bent ground electrode on the circuit to the matching layer (Cabrera-Munoz et al, 2019). All these extra processes not only increase the cost of the transducer but also cause the instability of the electrical connection.…”

Recent Advances in Transducers for Intravascular Ultrasound (IVUS) Imaging

“…Based on the porcine carotid artery phantom imaging evaluation results, the array provided a penetration depth > 5 mm for IVUS imaging. Following this work, Cabrera-Munoz et al [141] fabricated a 15 MHz side-looking phased array transducer as well, which was composed of 64-element of 2-2 PMN-PT composite. The fabricated array showed an aperture of 3.2 mm × 1.8 mm, which could be integrated into a 10 Fr catheter.…”

The Core of Medical Imaging: State of the Art and Perspectives on the Detectors

“…This is the reason why 3D ultrasound imaging methods based on 2-D array probes are continuing to improve in terms of fabrication and processing [7,8], and synthetic aperture ultrasound imaging [9,10]. Recently, the combination of miniaturized phased-array transducers and minimally invasive robotic surgery instruments is a further challenge in array development; preliminary phantom measurements demonstrate the feasibility to provide intraoperative image guidance and tissue characterization during endoscopic procedures [11].…”