Which tissue has the fastest propagation speed?

Which tissue has the fastest propagation speed?

• A. Bone
• B. Fat
• C. Liver
• D. Blood

Answer: (A)

The key idea is how fast ultrasound waves travel through different tissues. The speed of sound in a medium is mainly governed by how stiff the tissue is and, to a lesser extent, its density. Bone is very dense and rigid, so it transmits sound waves much faster than soft tissues. In numbers, bone can be around 4000 m/s or more, while soft tissues are typically about 1500–1600 m/s and fat is a bit softer, around 1400–1500 m/s. Blood, being a liquid, falls in the soft-tissue range as well. Because of this high stiffness and density contrast, bone gives the fastest propagation speed among these tissues.

The key idea is how fast ultrasound waves travel through different tissues. The speed of sound in a medium is mainly governed by how stiff the tissue is and, to a lesser extent, its density. Bone is very dense and rigid, so it transmits sound waves much faster than soft tissues. In numbers, bone can be around 4000 m/s or more, while soft tissues are typically about 1500–1600 m/s and fat is a bit softer, around 1400–1500 m/s. Blood, being a liquid, falls in the soft-tissue range as well. Because of this high stiffness and density contrast, bone gives the fastest propagation speed among these tissues.