IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control

The cover shows a Ring Transducer System and Measured Waveforms. The ring transducer is the circular assembly in the foreground connected by cables to electronics in the background. The ring transducer contains 2,048 elements with a 2.5-MHz center frequency, a 67% -6-dB bandwidth, and a 0.23-mm pitch arranged in a 150-mm diameter ring with a 25-mm elevation. The electronics are comprised of 128 independently programmable transmitters with 8-bit resolution, 16 receivers with 12-bit resolution and independently programmable time-variable gain, a 2,048:128 transmit multiplexer, and a 2,048:16 receive multiplexer. The measured waveforms are shown on a ±100-dB log scale. The waveforms were produced using a 48- mm tissue-mimicking cylindrical scattering phantom illuminated by a spatially limited pulsatile plane wave. The strong waves at ±180° near the beginning and end of the displayed time interval are from the near and far boundaries of the cylindrical phantom. The less strong waves with regular patterns between the boundary waves are from filaments and the boundary of scatterer-free cylinders in the phantom. The weak waves are from scatterers randomly distributed in the tissue-mimicking background material of the phantom. The photograph and measured waveforms were supplied by the Diagnostic Ultrasound Research Laboratory at the University of Rochester, Rochester, NY. See article on page 1707 for more detail. This work was supported by the National Cancer Institute Project CA74050 awarded to the University of Rochester. Image files available for download: CMYK Image (zipped), EPS format, 7.84 MB (24.8 MB decompressed); RGB Image, JPG Format, 293 KB