High Resolution Ultrasonic Imaging Using a Large Aperture Annular Array Transducer of P(VDF-TrFE) Copolymer
A 7.5 MHz concave annular array ultrasonic transducer comprising a piezoelectric film of vinylidene fluoride and trifluoroethylene copolymer, and its driving system has been developed for high resolution medical imaging. The transducer is composed of eight annular elements of equal areas and has a large aperture (70 mm) and a long radius of curvature (180 mm). With phase controlled electric driving pulses, the focal length can be varied dynamically from 150 to 200 mm. The transducer is scanned mechanically in a sector mode in a water bag container to which the objects to be examined are contacted. The acoustic field distribution, pulse waveform, and frequency response characteristics are analysed experimentally and theoretically. The consistency is quite satisfactory. The lateral resolution obtained is 0.5-1.0 mm over the focal zone, and the depth resolution is 0.3 mm. Clear and fine echotomographic images of the breasts and thyroid glands can be obtained with this imaging system.
KeywordsFluoride Dura Acoustics Hydrophone Vinylidene
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