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Two-Dimensional Arrays For Medical Ultrasound

S.W. Smith, G.E. Trahey, O.T. von Ramm

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The design, fabrication and evaluation of two-dimensional transducer arrays are described for medical ultrasound imaging. A 4 × 32, 2.8 MHz array was developed to use new signal processing techniques for improved B-scan imaging including elevation focusing, phase correction and synthetic aperture imaging. Laboratory measurements from typical array elements showed 50 Ω dB, and − dB pulse-echo angular response of 62°. Simulations of pulse-echo beam plots have shown grating lobes 20 dB below the main lobe at ±7° in the elevation direction. The complete 2-D array has been used for measurements of phase aberrations in breast, and the individual 32 element linear arrays have been used to obtain conventional B-scans. Several 16 × 16 arrays have also been developed for high speed volumetric imaging. These include 96 transmit elements and 32 receive channels. With a λ/4 matching layer, laboratory measurements show 50 Ω insertion loss of −72 dB, − dB fractional bandwidth of 63%, interelement crosstalk of &29 dB and − dB angular response of 25°. Pulse-echo sensitivity was improved by 21 dB through the use of integrated circuit preamplifiers of high impedance mounted in the transducer handle. In vivo cardiac, abdominal, and obstetric B-scans with elevation focusing, as well as high speed C-scans, have been obtained with these 2-D arrays.