Contrast B-mode imaging with M-mode, including the type of information each provides.

• A. B-mode shows 2D anatomy; M-mode tracks motion over time along a single line
• B. B-mode tracks motion; M-mode shows 3D volumes
• C. B-mode is Doppler-based; M-mode maps tissue stiffness
• D. B-mode shows color flow; M-mode shows spectral density

Answer: (A)

The main idea is that B-mode and M-mode serve different kinds of ultrasound information: B-mode provides a two-dimensional image of anatomy, while M-mode captures motion over time along a single line.

In B-mode, echoes are converted into brightness on a 2D image, so you see the structure and layout of tissues in a plane. M-mode, however, follows how tissues along a specific line move over time, plotting depth versus time to reveal motion of structures such as heart walls and valves with very high temporal resolution. This combination makes B-mode great for viewing anatomy and M-mode ideal for detailed motion tracking along one line.

The best description is that B-mode shows 2D anatomy and M-mode tracks motion over time along a single line. The other statements mix up what each mode measures: B-mode is not a motion-tracking method, nor does M-mode produce 3D volumes; B-mode is not Doppler-based, and M-mode does not map tissue stiffness. Color flow and spectral density pertain to Doppler imaging, not to these two modes.