Experimental validation of a theoretical framework to predict radiation force displacement of contrast agents

This research presents direct observations of the effect of radiation force on an individual microbubble over a single acoustic pulse. A model that accounts for the radial oscillation of the bubble, in addition to drag terms, which account for the translating and resonating bubble, is shown to accurately predict trends in observed displacement. A modified version of the Rayleigh-Plesset equation is used to estimate the radius-time behavior of insonified microbubbles. High-speed photography of insonified bubbles with a time resolution of 10 ns allows visualization of radial oscillations in addition to observations of translation due to radiation force. Displacement trends for the translation of microbubbles due to radiation force are accurately predicted by the model. Data indicate that with optimized center frequency, acoustic pressure, pulse length, and pulse-repetition frequency, radiation force has the potential to displace microbubbles large distances with clinical parameters. In addition, our results indicate that the effects of radiation force can influence the velocity of flowing contrast agents, creating a biased velocity estimate.