Figure 11.

Schematic drawing illustrates the directions of the central beam and lateral dispersion of residual off-axis beams (side and grating lobes) (A). The lateral dispersion of US beams can be clearly observed with a lot of coupling agents in between the needle and transducer (B). The side lobe artifact can be observed inside the cystic lesion (C). Yellow arrow: side lobe; red arrowheads: grating lobes; white arrowhead: nail plate. White arrowhead: the ghost image on the main axis of the US beam. Yellow arrowhead: the object on the path of the side lobe that causes the side lobe artifact.