The potential of transskull ultrasound therapy using the maximum available skull surface area

Contingent with previous studies, the transskull ultrasound field is reexamined numerically by utilizing the maximum available skull surface area. The source is assumed to be right on the outer skull surface and phase correction is adopted to obtain a sharp focus at a desired location. A digitized skull profile was obtained from MR images of a volunteer. With no phase correction, there is no apparent transskull focus. With phase correction, a sharp transskull focus is obtained at the desired location. Both pressure and SAR gains are examined, and it is shown that the skull over heating problem can be well overcome. Maximum pressure and SAR gains of above 70 and 800 are observed at 625 kHz. By specifying the phase correction for different locations, the focus can be successfully moved inside most part of the brain volume