2aEA11. A noninvasive ultrasonic technique for measuring the dynamic properties of biological tissues.

Session: Tuesday Morning, December 3

Time: 10:45

Author: James J. Finneran
Location: Dept. of Mech. Eng., Ohio State Univ., 206 W. 18th Ave., Columbus, OH 43210
Author: Mardi C. Hastings
Location: Dept. of Mech. Eng., Ohio State Univ., 206 W. 18th Ave., Columbus, OH 43210


A noninvasive, continuous wave ultrasonic technique has been used to measure the amplitude and phase of biological tissues in response to acoustically induced vibrations. Tissues exposed to a low-frequency sound field were simultaneously insonified by a low-power, continuous wave ultrasonic source operating at 15 MHz. The motion of the target (due to the low-frequency acoustic field) caused ultrasound scattered by the target to be phase modulated. A separate ultrasonic transducer acted as the receiver. Target amplitude information was obtained directly from the receiver output using a high-frequency spectrum analyzer; phase information was obtained by first demodulating the received signal using a double-balanced mixer and low-pass filter. This paper examines the operation of the measurement system, particularly the phase-measurement technique. The spatial resolution of the ultrasonic measurement system is also examined. The theoretical model for the ultrasonic receiver field coupled existing models for focused piston radiators and for pulse-echo ultrasonic fields. Experimental measurements of the resulting receiver fields compare favorably with theoretical predictions. [Work supported by ONR Grant No. N00014-94-1-0337.]

ASA 132nd meeting - Hawaii, December 1996