Which statement describes a characteristic of A-mode imaging?

• A. A-mode is a two-dimensional grayscale cross-section
• B. A-mode uses color Doppler imaging
• C. A-mode is a one-dimensional plot of echo amplitude versus depth
• D. A-mode produces three-dimensional volume renders

Answer: (C)

A-mode is the one-dimensional depth profile of echoes. It shows echo strength as a function of depth along the ultrasound beam. When a pulse is sent, echoes from interfaces at different depths return and appear as spikes. The position of each spike corresponds to the reflector’s depth, and the spike height represents the echo amplitude (reflectivity). Because it only provides information along a single line, it does not produce a two-dimensional grayscale image (that’s B-mode), it doesn’t use color Doppler for flow, and it doesn’t render three-dimensional volumes.