What happens to attenuation as frequency increases?

• A. Decreases
• B. Increases
• C. Stays the same
• D. Depends on material

Answer: (B)

Attenuation increases with frequency because higher-frequency ultrasound loses more energy as it travels through tissue. Attenuation comes from both absorption (conversion of sound energy into heat) and scattering, and in most biological media the amount of energy removed per centimeter rises as frequency goes up. That means the attenuation coefficient is larger at higher frequencies, so the beam is weakened more quickly as it moves deeper. While the exact rate depends on the material, the general trend in soft tissue is upward with frequency. So, as frequency increases, attenuation increases.