Which ultrasound mode is primarily used to assess motion, such as cardiac structures?

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

Answer: (C)

Tracking motion over time is what this item tests. M-mode ultrasound records depth along a single line as time progresses, producing a motion trace of structures along that line. This gives exceptionally high temporal resolution, so rapid cardiac movements—such as valve opening and closing, and how the walls of the chambers move during systole and diastole—can be seen and measured precisely. That precision is why M-mode is the go-to when you need exact timing and excursion data for cardiac structures.

A-mode provides only a one-dimensional depth signal with no motion context, so it can’t show how structures move over time. B-mode offers a two-dimensional image of anatomy but with lower temporal resolution, making dynamic events harder to quantify in real time. C-mode isn’t commonly used for assessing motion in clinical practice.