Experimental and theoretical analysis of individual contrast agent behavior

An improved understanding of contrast agent behavior may yield more sophisticated bubble detection techniques. In this study, the optical measurements of single bubble oscillations during insonation are compared directly to theoretical predictions. These results are then used to aid in the understanding of the effects of transmission and bubble parameters on the bubble oscillations and resulting received echoes. A Rayleigh-Plesset-like bubble equation with additional shell terms is solved for the time dependent bubble radius and wall velocity, and these outputs are also used to formulate the predicted echo from a single encapsulated bubble. The experimental and theoretical radius-time curves are in good agreement; with a consistent, predictable response from the lipid-shelled agent with varying amplitude, phase and length of the transmission pulses. The radius-time curves of the albumin-shelled agent Optison are less predictable due to its asymmetric oscillations. Observations of the effects of transmitted phase and the corresponding predicted echoes are consistent with previous experimental results. These results demonstrate that the transmission of two pulses with opposite phases will yield similar time domain echoes with the echo from the pulse with rarefaction first (180°) having a mean frequency that is higher than the compression first response (0°).