The _____ is an important tissue property that influences the amount of reflection.

The _____ is an important tissue property that influences the amount of reflection.

• A. Attenuation
• B. Propagation speed
• C. Acoustic impedance
• D. Density

Answer: (C)

Reflection at tissue interfaces is governed by acoustic impedance. Acoustic impedance, Z, is the product of tissue density (ρ) and the speed of sound in that tissue (c), so Z = ρc. When an ultrasound wave reaches a boundary between two tissues, the amount that reflects back depends on how different their impedances are. A large mismatch yields a strong echo, while a small mismatch gives a weaker echo or mostly transmission. Attenuation describes energy loss as the wave travels through tissue, not how much reflects at the boundary, and density alone doesn’t determine reflection—the relevant factor is impedance, which combines density and speed of sound.

Reflection at tissue interfaces is governed by acoustic impedance. Acoustic impedance, Z, is the product of tissue density (ρ) and the speed of sound in that tissue (c), so Z = ρc. When an ultrasound wave reaches a boundary between two tissues, the amount that reflects back depends on how different their impedances are. A large mismatch yields a strong echo, while a small mismatch gives a weaker echo or mostly transmission. Attenuation describes energy loss as the wave travels through tissue, not how much reflects at the boundary, and density alone doesn’t determine reflection—the relevant factor is impedance, which combines density and speed of sound.