Broadband time-domain reflectometry measurement of attenuation and phase velocity in highly attenuating suspensions with application to the ultrasound contrast medium Albunex (R)

We describe a technique for broadband measurements of the attenuation coeff icient and phase velocity of highly attenuating liquid suspensions. To vali date the technique we apply it to the ultrasound contrast agent Albunex(R) at concentrations ranging from 0.69x10(6) particles/ml to 364x10(6) particl es/mL. These longitudinal wave measurements were performed on Albunex suspe nsions maintained at 37 degrees C in a special time-domain reflectometer de signed and constructed in our laboratory, The frequency-dependent attenuati on coefficients and phase velocities obtained in the reflectometer are comp ared to broadband through-transmission measurements of these same quantitie s, which were also performed in our laboratory. Although comparison data be tween the two techniques are only available at lower concentrations, the ag reement is quite good and serves to validate the methods described in this paper. (C) 2000 Acoustical Society of America. [S0001-4966(00)05507-7].