Which factor determines acoustic impedance in soft tissue?

Which factor determines acoustic impedance in soft tissue?

• A. Attenuation
• B. Frequency
• C. Density
• D. Absorption

Answer: (C)

Acoustic impedance is about how much a medium resists the ultrasound wave as it travels, and it’s defined by Z = ρ c, the product of density and the speed of sound. In soft tissue, the speed of sound doesn’t vary a lot from one tissue to another, so the changes in impedance mainly come from density differences. Attenuation and absorption describe energy loss, not the boundary resistance that impedance captures, and frequency mainly affects how waves attenuate or disperse rather than the intrinsic impedance value. So density is the primary factor that determines acoustic impedance in soft tissue.

Acoustic impedance is about how much a medium resists the ultrasound wave as it travels, and it’s defined by Z = ρ c, the product of density and the speed of sound. In soft tissue, the speed of sound doesn’t vary a lot from one tissue to another, so the changes in impedance mainly come from density differences. Attenuation and absorption describe energy loss, not the boundary resistance that impedance captures, and frequency mainly affects how waves attenuate or disperse rather than the intrinsic impedance value. So density is the primary factor that determines acoustic impedance in soft tissue.