A dual-layer transducer array for 3-D rectilinear imaging

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 56; no. 1; pp. 204 - 212
• Main Authors: Yen, J.T., Chi Hyung Seo, Awad, S.I., Jeong, J.S.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.01.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic signal processing; Acoustics; Arrays; Biological and medical sciences; Breast; Carotid arteries; Ceramics - chemistry; Computer Simulation; Copper; Counting; Cysts; Design engineering; Exact sciences and technology; Fabrication; Fundamental areas of phenomenology (including applications); Imaging; Imaging, Three-Dimensional - instrumentation; Integrated circuit interconnections; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Miscellaneous. Technology; Models, Theoretical; Musculoskeletal system; Noise levels; Physics; Prototypes; Reproducibility of Results; Sensitivity and Specificity; Signal Processing, Computer-Assisted; Transducers; Transmitters; Ultrasonic investigative techniques; Ultrasonic variables measurement; Ultrasonography - instrumentation; Human; Crosstalk; PZT; Artery; Piezoelectric ceramics; Beam forming; Vinylidene fluoride copolymer; Synthetic aperture; Carotid; Breast; Medical imagery; Feasibility; Tridimensional image; Acoustic antenna; Circulatory system; Mammary gland; Plane antenna
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2009.1020

Very large element counts (16,000-65,000) are required for 2-D arrays for 3-D rectilinear imaging. The difficulties in fabricating and interconnecting 2-D arrays with a large number of elements (>5,000) have limited the development of suitable transducers for 3-D rectilinear imaging. In this paper, we propose an alternative solution to this problem by using a dual-layer transducer array design. This design consists of 2 perpendicular 1-D arrays for clinical 3-D imaging of targets near the transducer. These targets include the breast, carotid artery, and musculoskeletal system. This transducer design reduces the fabrication complexity and the channel count, making 3-D rectilinear imaging more realizable. With this design, an effective N times N 2-D array can be developed using only N transmitters and N receivers. This benefit becomes very significant when N becomes greater than 128, for example. To demonstrate feasibility, we constructed a 4 times 4 cm prototype dual-layer array. The transmit array uses diced PZT-5H elements, and the receive array is a single sheet of un-diced P[VDF-TrFE] copolymer. The receive elements are defined by the copper traces on the flexible interconnect circuit. The measured -6 dB fractional bandwidth was 80% with a center frequency of 4.8 MHz. At 5 MHz, the nearest neighbor crosstalk of the PZT array and PVDF array was -30.4 plusmn 3.1 dB and -28.8 plusmn 3.7 dB, respectively. This dual-layer transducer was interfaced with an Ultrasonix Sonix RP system, and a synthetic aperture 3-D data set was acquired. We then performed offline 3-D beamforming to obtain volumes of nylon wire targets. The theoretical lateral beamwidth was 0.52 mm compared with measured beamwidths of 0.65 mm and 0.67 mm in azimuth and elevation, respectively. Then, 3-D images of an 8 mm diameter anechoic cyst phantom were also acquired.