Which of the following is not one of the primary attenuation components?

• A. Scattering
• B. Deflection
• C. Reflection
• D. Absorption

Answer: (B)

Attenuation refers to the decrease in ultrasound intensity as it travels through tissue. The three main mechanisms are absorption, scattering, and reflection. Absorption converts part of the energy to heat; scattering redirects energy in many directions away from the original path; reflection redirects energy back toward the transducer at interfaces. Deflection describes a change in direction but isn’t a separate attenuation mechanism by itself—the energy change due to deflection is accounted for by reflection and scattering. So deflection is not one of the primary attenuation components.