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 (P _np), 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 (V _OPT) and acoustical evaluation (V _US). In addition, the maxima of V _OPT and V _US were correlated (R = 0.665) and showed a similar trend proportional to the square of P _np. 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.