Broadband through-transmission signal loss measurements of Albunex(R) suspensions at concentrations approaching in vivo doses

Broadband normalized signal loss of commercially available Albunex(R), an ultrasonic contrast agent, was measured in vitro at concentrations approaching those which may be found in vivo for clinical doses. The measurements were made using a novel specimen chamber, careful material handling procedures, and a broadband square wave pulser system. Results were obtained over the full bandwidth of the experimental system (1 to 20 MHz) at concentrations up to 1.9 X 10(6) microspheres/mL. Further results were obtained over a partial bandwidth of the experimental system at concentrations up to 1.5 X 10(7) microspheres/mL. The frequency-dependent signal loss exhibited a peak for all concentrations investigated. In the meaningful bandwidth of the system, the signal loss (expressed in dB) was directly proportional to microsphere concentration. The experimental results for normalized signal loss were compared with predictions from a linear single-scattering model for encapsulated bubbles. The experimental data was used to estimate values for the two adjustable parameters in the model: microsphere shell elasticity (4200+/-1000 dyn/cm) and friction (0.0054+/-0.0015 dyn s/cm). (C) 1997 Acoustical Society of America.