Hydrophone scans result. 2D plot of hydrophone scans without (a) and with (b) the plastic skull in the US beam path. Line plots in the x-direction (indicated by yellow arrows) and in the y-direction (green arrows) for the two cases are shown in (c) and (d), respectively. All intensities are normalized to the maximum value in the water-only scan. The US focus is steered 5 mm in the x- and y-directions, relative to the geometric focus. Beam aberration is not significant; however, an intensity drop of about 85% and slight shift in the y-direction are seen to occur when focusing through the skull. (e–h) Corresponding data from the lamb skullcap after all soft tissue was removed. In this case, an intensity drop of about 70% and only slight beam aberration are observed.