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Crosstalk reduction in a polyvinylidene fluoride (PVDF) integrated ultrasound transducer array with a micromachined diaphragm structure is reported. Three sets of linear arrays with nine 1 mmx1 mm elements on dielectric diaphragms have been made. They were fabricated with (1) a solid substrate, (2) a single large diaphragm window underneath the entire array, and (3) a small diaphragm window (SW) for each array element. To estimate crosstalk and fringe field effects in each array, the authors measured each array's angular response in the far field of an unfocused source transducer. A Fourier transform analysis was then performed on the measured data to obtain each array's directivity pattern, which in turn was fitted to theoretical curves based on a crosstalk model. Crosstalk-related parameters have been extracted from curve-fitting and their values show that the array with the SW structure for each element has the least electrical and acoustical crosstalk and fringe field effects.

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A prototype 16-element needle hydrophone array has been designed, fabricated and characterized. The primary use of this array is to provide acoustic feedback during ultrasound hyperthermia treatments. This feedback is necessary to compensate phased array heating patterns for patient motion and tissue inhomogeneities in real time. The array consists of a PVDF covered silicon substrate carrier which contains the signal electrodes of the individual acoustic sensors. Tests have shown that the array is sensitive to both pulsed and continuous ultrasound (943 kHz) excitation and can be used in tissue media. A complete description of the needle array, element cross-coupling measurements, beam profile measurements, calibration procedures and sensitivity analyses in both water and tissue are presented.

It is widely believed that judicious application of microelectronics is one of the keys to developing future ultrasound systems, with many more channels and associated improvements in image quality. This paper will describe recent work on techniques for applying microelectronics and related microfabrication technology to different aspects of ultrasound imaging systems.