In B-mode, which axis represents Nothing?

• A. X-axis
• B. Y-axis
• C. Z-axis
• D. None

Answer: (B)

In B-mode imaging, the image is a 2D map where brightness encodes how strong the echo is at each point. The two spatial directions on the screen correspond to where the scan line is across the image (left to right) and how deep into the tissue the echo originated (toward the transducer). The brightness dimension is what carries the tissue information, not an additional spatial quantity. In this phrasing, the vertical axis is described as representing Nothing—there isn’t a separate physical parameter attached to that axis beyond depth positioning. The horizontal axis carries the lateral scan position, there is no separate Z-axis in this 2D display, and None wouldn’t apply since there is a defined axis for depth. Therefore, the axis labeled as Nothing is the vertical (Y) axis.