On a B-mode image, a high acoustic impedance mismatch at an interface is displayed as which?

On a B-mode image, a high acoustic impedance mismatch at an interface is displayed as which?

• A. A tall spike
• B. A small spike
• C. A dark dot
• D. A bright dot

Answer: (D)

Brightness on a B-mode image reflects the strength of the returning ultrasound echo. When two tissues have a large acoustic impedance difference, most of the ultrasound energy is reflected at that interface, producing a strong echo. That strong echo appears as a bright spot at the depth of the interface. So a high impedance mismatch is shown as a bright dot on the image because its amplitude—and thus its brightness—is high. A smaller or weaker mismatch would yield a less bright or smaller signal, and a dark area would indicate little to no reflection. The bright dot best captures the idea of a pronounced, localized reflection from a strong impedance boundary.

Brightness on a B-mode image reflects the strength of the returning ultrasound echo. When two tissues have a large acoustic impedance difference, most of the ultrasound energy is reflected at that interface, producing a strong echo. That strong echo appears as a bright spot at the depth of the interface. So a high impedance mismatch is shown as a bright dot on the image because its amplitude—and thus its brightness—is high. A smaller or weaker mismatch would yield a less bright or smaller signal, and a dark area would indicate little to no reflection. The bright dot best captures the idea of a pronounced, localized reflection from a strong impedance boundary.