How does attenuation in bone compare to soft tissue for the same frequency?

• A. Attenuation is lower in bone, improving penetration
• B. Attenuation is much higher in bone, leading to poorer penetration
• C. Attenuation is the same in both
• D. Bone attenuation is highly variable and cannot be compared

Answer: (B)

Attenuation is the loss of ultrasound energy as it travels, mainly from absorption and scattering. Bone has a much higher attenuation coefficient than soft tissue at the same frequency because its dense, mineralized structure absorbs more energy and scatters sound more effectively. This causes the ultrasound beam to lose amplitude rapidly as it passes through bone, so penetration beyond bone is quite poor compared with soft tissue. The effect is amplified at higher frequencies, since attenuation increases with frequency, making the contrast between bone and soft tissue even more pronounced. So, attenuation is much higher in bone, leading to poorer penetration.