Produção Nacional
Revisado por pares
Ultrasonic wave speed measurement using the time-delay profile of rf-backscattered signals: Simulation and experimental results
2002; Acoustical Society of America; Volume: 111; Issue: 3 Linguagem: Inglês
10.1121/1.1445787
ISSN1520-9024
AutoresFernando Oscar Ruttkay Pereira, João Carlos Machado, Wagner Coelho de Albuquerque Pereira,
Tópico(s)Photoacoustic and Ultrasonic Imaging
ResumoConventional methods determine the ultrasonic wave speed measuring the medium path length propagated by a pulsed wave and the corresponding time-of-flight. In this work, the wave speed is determined without the need of the path length. A transmit transducer sends a pulsed wave into the medium (wave speed constant along the beam axis) and the backscattered signal is collected by a hydrophone placed at two distinct positions near the transmitted beam. The time-delay profile, between gated windows of the two rf-signals received by the hydrophone, is determined using a cross-correlation method. Also, a theoretical time-delay profile is determined considering the wave speed as a parameter. The estimated wave speed is obtained upon minimization of the rms error between theoretical and experimental time-delay profiles. A PZT conically focused transmitting transducer with center frequency of 3.3 MHz, focal depth of 30 mm, and beam full width (-3 dB) of 2 mm at the focus was used together with a PZT hydrophone (0.8 mm of aperture). The method was applied to three phantoms (wave speed of 1220, 1540, and 1720 m/s) and, in vitro, to fresh bovine liver sample, immersed in a temperature-controlled water bath. The results present a relative speed error less than 3% when compared with the sound speed obtained by a conventional method.
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