What is the relationship between ultrasound frequency and attenuation?

• A. Attenuation decreases as frequency increases
• B. Attenuation is independent of frequency
• C. Attenuation increases as frequency increases
• D. Attenuation occurs only at tissue interfaces

Answer: (C)

The main idea is that attenuation in ultrasound scales with frequency. As frequency increases, more of the sound energy is absorbed and scattered as it travels through tissue, so the signal loses amplitude more quickly with distance. In soft tissue, the attenuation coefficient is roughly proportional to frequency (about 0.5 dB/cm/MHz), meaning doubling the frequency roughly doubles the attenuation over the same path length. This is why higher-frequency probes provide better axial resolution but don’t image as deeply as lower-frequency probes. The other statements don’t fit because attenuation is not weaker at higher frequencies, nor is it independent of frequency, and it isn’t limited only to tissue interfaces—it occurs throughout propagation due to absorption and scattering.