Ultrasonic wave speed measurement using the time-delay profile of rf-backscattered signals: Simulation and experimental results

被引:17
作者
Pereira, FR
Machado, JC
Pereira, WCA
机构
[1] Univ Estado Rio De Janeiro, UERJ, IPRJ, Inst Politec, BR-28601970 Nova Friburgo, RJ, Brazil
[2] Univ Fed Rio de Janeiro, COPPE, Biomed Engn Program, BR-21945970 Rio De Janeiro, RJ, Brazil
关键词
D O I
10.1121/1.1445787
中图分类号
O42 [声学];
学科分类号
070206 ; 082403 ;
摘要
Conventional 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. (C) 2002 Acoustical Society of America.
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页码:1445 / 1453
页数:9
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