In A-mode ultrasound displays, how is depth represented?

• A. Depth is shown on the vertical axis with spikes proportional to reflectivity
• B. The image is a real-time 2D grayscale image
• C. Color flow mapping is displayed
• D. Doppler spectral waveform is shown

Answer: (A)

A-mode displays provide a one-dimensional depth profile: depth is shown along the vertical axis, and each echo appears as a spike whose height is proportional to the echo’s amplitude (reflectivity). This means you’re reading how deep a tissue interface is, based on how strong the return signal is, not forming a full image. The other displays describe B-mode or Doppler techniques, which produce real-time 2D grayscale images, color flow maps, or Doppler waveforms, not the single-line depth profile of A-mode.