Fig. 2

Depiction of the three HIFU beam geometries used in this study. a-c Example coronal MR images showing heat deposition from single focusing and the two multi-focus patterns. a Single focus beam. b Four points placed on an imaginary ring of diameter 4 mm. Individual foci were not resolvable with the given scan parameters, and thus appears similar to a single-focus in the image. c The same four points on a ring of diameter 8 mm. d Rayleigh-Sommerfeld simulated pressure field, normalized such that the single focus peak is unity, and the 4 and 8 mm foci are 0.7 and 0.6 respectively