Fig. 5.

Simultaneous observation of HIFU-induced cavitation bubble activity performed with the high-speed camera and Doppler ultrasound for two pulse sequences: color Doppler ((a) and (b)) and interleaving Doppler ((c) and (d)). The HIFU transducer (focal region size 16 mm × 1.5 mm at the −6 dB level) is located to the left of all images; arrows indicate the lateral position of the focus. Cavitation bubbles were readily observed in both high-speed camera images, (a) and (c), as small black dots scattered throughout the focal region. The sizes and positions of these bubble distributions corresponded to the regions of alternating dark red and blue color in color Doppler regime (b), and to the bright color mosaic in the interleaving Doppler regime (d).