Comparable analysis of bubble translation due to acoustic radiation force based on simultaneous acoustical and optical observation

Contrast-enhanced ultrasound imaging using acoustic radiation force, called contrast-enhanced active Doppler ultrasound (CEADUS) imaging, has been proposed for visualizing lymph channels filled with stationary fluid. Based on optical observations and acoustical evaluation, the behaviour of bubbles in a simulated channel during ultrasound exposure was investigated under four conditions for negative peak sound pressure (Pnp), at centre frequency of ultrasound and pulse repetition frequency of 15 MHz and 1 kHz, respectively. There was good correlation between the time changes of mean translational velocity for optical evaluation (VOPT) and acoustical evaluation (VUS). In addition, the maxima of VOPT and VUS were correlated (R = 0.665) and showed a similar trend proportional to the square of Pnp. These results strongly suggest that the acoustically-evaluated bubble translation has information equal to optically-evaluated one, meaning that the simultaneous observation system is useful to understand the bubble behaviours under CEADUS imaging.