Which mode creates a 2D qualitative cross-sectional image using multiple sound beams?

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

Answer: (B)

Brightness mode builds a two-dimensional cross-sectional image by steering many ultrasound beams across a plane. Each beam provides depth information and echo brightness is mapped to a pixel, so the resulting grayscale image shows tissue interfaces and anatomy in real time. This is why it’s the standard mode for 2D ultrasound imaging.

A-mode, by contrast, displays echoes along a single depth line as a graph of amplitude versus depth, offering a one-dimensional view. M-mode tracks motion over time along a single line, giving a time-based strip rather than a full cross-section. Doppler mode focuses on frequency shifts to assess flow, outputting spectral or color flow information rather than a tissue anatomy image.