Which ultrasound mode provides the basic two-dimensional grayscale image?

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

Answer: (B)

Two-dimensional grayscale ultrasound images come from brightness mode. The system sends pulses and scans many lines across the area; for each line, the strength of echoes at each depth is converted into a brightness value. When thousands of these brightness points along many lines are put together, a cross-sectional image appears, with grayscale levels reflecting how strongly tissues reflect ultrasound. A-mode, by contrast, plots echo amplitude versus depth along a single line, giving a one-dimensional spike trace rather than an image. M-mode shows motion along a single line over time, useful for tracking structures such as heart valves. C-mode isn’t used for standard 2D grayscale anatomy imaging.