How does increasing the frequency of ultrasound affect its attenuation in soft tissue?

• A. Attenuation decreases
• B. Attenuation remains the same
• C. Attenuation increases
• D. Attenuation depends on the medium

Answer: (C)

Increasing the frequency of ultrasound leads to increased attenuation in soft tissue because higher frequency waves have shorter wavelengths, which results in more scattering and absorption as they interact with the various structures and interfaces within the tissue.

Attenuation refers to the reduction of the amplitude and intensity of the ultrasound waves as they propagate through a medium. In soft tissues, when the frequency is increased, the energy of the ultrasound wave is absorbed more quickly, and the wave experiences greater scattering due to interactions with small structures within the tissue. This is why higher frequency ultrasound is generally less penetrating; it can provide better resolution due to its ability to differentiate smaller structures, but it does not travel as far within the tissue because of the increased rate of attenuation.

By contrast, lower frequency ultrasound waves have longer wavelengths, which can travel further with less attenuation, making them more suitable for imaging deeper tissues. The attenuation behavior is inherently linked to the frequency of the ultrasound, establishing a clear relationship where an increase in frequency results in an increase in attenuation.