Fig. 2

a B-mode images of the phantom before and after HIFU treatment with the associated bubble cloud appearing in the latter. b The subtraction of the two images in (a). c The outline of the bubble clouds determined using methods described in the text. The red square marks the upper half of the bubble cloud. d The averaged outline over repeated experiments was obtained (solid line). The dashed lines represent the averaged outline ± one standard deviation of the outline (n ≥ 4)