Time-resolved measurement of bubble cavitation by using power Doppler ultrasound image

In this study, a novel measurement method for a secondary ultrasound wave irradiated by microbubble cavitation is proposed. High-intensity ultrasound (h-US, 1.0-1.5 MPa), which produces bubble cavitation, is irradiated with a fixed time delay after introducing imaging US, whose frequency is different from that of the h-US. The bubble cavitation signal (BCS) is detected by the signal-processing unit of an ultrasound power Doppler imaging instrument. By this method, both a spatially resolved bubble image (S-image) and the temporal transition of the BCS (T-image) are monitored simultaneously. A feature of the method is that the BCS is observed in situ with sub-mu s time resolution. The accuracy of the method is evaluated and it is found that the maximum deviation of the amplitude of the simulated BCS is 4.80%. This method is applied to measure the BCS of ultrasound contrast agent microbubbles. As a result, the dependence of the inherent temporal transition of the BCS on the sound pressure of the h-US (0.6-1.2 MPa) is observed. (C) 2017 The Japan Society of Applied Physics.