Figure 9b. Proper positioning of the probe during US-guided directional vacuum-assisted core biopsy. (a) US image shows that the probe (small arrows) is posterior to the lesion, which is nevertheless within the limits of the probe aperture. The aperture can be clearly visualized owing to the discontinuity of the anterior wall of the probe and the ring-down artifact on the opposite side of the aperture (large arrows). (b) US image shows that the cutter (arrow) has been advanced through the lesion.