Experimental verification of ensemble model for scattering by microbubbles population in a contrast agent

A theoretical contrast agent model, extending existing single bubble models to a population of simulated bubbles, was previously reported to produce time-domain scattered signals which compared well qualitatively to experiments. In this paper, experiments were carried out to test this model quantitatively. DPM-115 (Dupont-Merck Inc) flowing in a chamber was exposed to 5 MHz pulsed ultrasound with various bandwidths. Scattered signals were detected at 90° by a broadband receive transducer. The experimental results generally confirm our model for predicting scattered signals, but the measured second harmonic scattering is 10 dB lower than the theoretical prediction. It was also observed that scattering is increased at high transmitted amplitude (>1.5 MPa). The disruptible shell is believed to be a possible cause for both effects, and it is suggested that the shell is very important in understanding the acoustic reponse of contrast agent.