Which mode is characterized by Time on the x-axis?

• A. A-mode
• B. B-mode
• C. M-mode
• D. Doppler mode

Answer: (C)

Time on the x-axis is the hallmark of motion mode. In this mode, you’re tracking echoes along a single scan line as time passes, so the horizontal axis represents time while the vertical axis shows depth (distance from the transducer). This setup lets you see how structures move over the cardiac cycle on one line, which is exactly what M-mode is designed to display.

By contrast, A-mode plots echo amplitude against depth along the beam, so depth is the primary axis. B-mode creates a two-dimensional grayscale image, with spatial positions rather than time as the main axis. Doppler mode is about measuring flow or velocity, typically shown as a velocity-versus-time waveform or color flow, not a simple depth-versus-time trace.