The brightness of the dot in B-mode indicates the ______.

• A. Strength of the reflection
• B. Depth of reflector
• C. Distance to transducer
• D. Frequency of the pulse

Answer: (A)

In B-mode imaging, each dot represents an echo from a tissue interface at a certain depth, and the brightness of that dot is tied to the amplitude of that echo. A stronger reflection happens when there’s a larger impedance mismatch at the interface, producing a brighter dot. A weaker reflection or more attenuated signal appears dimmer, and no echo shows up as black. The vertical position of the dot encodes depth, not its brightness, so depth or distance to the transducer isn’t what brightness measures. The pulse frequency influences resolution and how deeply the ultrasound can penetrate, but it doesn’t determine the brightness of a single echo. So the brightness best reflects the strength of the reflection.