Fig. 2. Pressure field characterization with free-water and transcranial propagation.

(A) Peak-negative pressure measured in free water in the lateral-axial plane with steering at 0 mm, 2 mm, 4 mm, and 6 mm in the lateral direction. The axes were centered at the peak-pressure position. (B) Peak-negative pressure measured in free water in the lateral-elevation plane with steering at 0 mm, 2 mm, 4 mm, and 6 mm in the lateral direction. The plane was placed at the peak position in the axial direction (0 mm in panel A; 0 mm in each axis indicates the focus center without steering). Aperture sub-sampling artifacts appear in the form of a distributed noise rather than well-formed grating lobes owing to the random element distribution. (C) Beam profiles in the lateral and axial directions. The profiles were sampled along the beam axis (axial) and along a perpendicular segment placed at the peak pressure location (lateral) as shown in Supplementary Fig. 1. (D) Hydrophone measurement setup with excised skull flap attached to the clip-on holder. The rostral end of the skull is on the right side of the picture. AP: anteroposterior. ML: mediolateral. DV: dorsoventral. (E) Peak-negative pressure measured in the coronal and sagittal planes. The axes were centered at the peak-pressure location. (F) Peak-negative pressure measured in the axial plane with steering at 0 mm and 2 mm in the lateral direction. The plane was placed at the peak location in the coronal plane. (G) Beam profiles in the mediolateral and dorsoventral directions without steering.