In ultrasound, what does echogenicity describe and what does a completely anechoic structure indicate?

• A. Echogenicity describes tissue attenuation; anechoic structures are highly echogenic.
• B. Echogenicity describes tissue reflecting sound; anechoic structures produce no internal echoes, indicating fluid.
• C. Echogenicity describes tissue density; anechoic structures contain air.
• D. Echogenicity describes tissue motion; anechoic structures indicate uniform movement.

Answer: (B)

In ultrasound, echogenicity is about how strongly a structure reflects the sound waves, which shows up as brightness on the image. A completely anechoic structure has no internal echoes at all, so it appears completely black. This pattern is typical of fluid-filled spaces, because fluids transmit sound with minimal reflection or scattering, unlike solid tissues that reflect more and appear brighter. So echogenicity describes reflectivity, and a blank (no echoes) interior signals fluid content.

The other ideas mix in concepts like attenuation, density, or motion, which aren’t what echogenicity measures. Attenuation is about how the signal weakens with depth, density is a material property, and motion refers to movement rather than how the tissue reflects sound.