Which statement best describes the relationship between B-mode and M-mode imaging?

• A. B-mode provides a grayscale image, while M-mode provides a motion trace along a line over time
• B. M-mode provides a grayscale image, while B-mode provides a motion trace
• C. Both rely on color Doppler data
• D. Both provide direct tissue stiffness mapping

Answer: (A)

The key idea is understanding what each ultrasound mode actually shows. B-mode, or brightness mode, creates a two-dimensional grayscale image by sweeping the ultrasound beam across tissue and converting the strength of each echo into a brightness level on a grid. It’s like a standard anatomy image that shows different tissues in shades of gray.

M-mode, or motion mode, looks at movement along a single scan line over time. It records how the depth of echoes along that line changes as time passes, producing a one-dimensional trace that shows motion—handy for tracking how structures move, such as heart walls and valves.

So, the statement that correctly describes their relationship is that B-mode provides a grayscale image, while M-mode provides a motion trace along a line over time. The other options mix up what each mode represents or bring in features (like color Doppler or tissue stiffness) that aren’t inherent to these two modes.