Figure 3
Representative acoustic images of vaporization fields (microbubble clouds) generated by the application of continuous wave HIFU. HIFU was applied at 1 MHz for 20 s at intensities of 140, 390, and 650 W/cm2 (PNP = 2, 3, and 4 MPa) to albumin-acrylamide phantoms containing PFC nanodroplets over a concentration range from 105 to 108 ND per milliliter. The progressive changes in the shape and location of the microbubble clouds with increasing PSNE concentrations can be seen. The shape change follows a predictable pattern from cigar (prolate ellipsoid) to tadpole (asymmetric ellipsoid) to oblate ellipsoid, as vaporization concentrates in prefocal regions.