FREQUENCY-DEPENDENCE OF ACOUSTIC BACKSCATTER FROM 5 TO 65 MHZ (0.06-LESS-THAN-KA-LESS-THAN-4.0) OF POLYSTYRENE BEADS IN AGAROSE

Attenuation and compensated backscatter from suspensions of random dis tributions of polystyrene beads in agarose are reported across a broad , continuous range of frequencies including frequencies which are curr ently of interest in the emerging fields of acoustic backscatter micro scopy and intravascular imaging. Data are reported over the range of k a from 0.06 to 4, where k is the magnitude of the ultrasonic wave vect or and a is the radius of the beads. The attenuation coefficient exhib its a linear dependence on frequency for ka much less than 1 and more complex behavior at larger values of ka. The measured frequency depend ence of the compensated backscatter was consistent with the frequency dependence of the differential backscatter cross section for a single polystyrene sphere throughout the range of ka investigated. (C) 1996 A coustical Society of America.