What are the three attenuation components in ultrasound?

• A. Scattering, Reflection, and Absorption
• B. Attenuation, Scattering, and Refraction
• C. Reflection, Scattering, and Diffraction
• D. Absorption, Reflection, and Transmission

Answer: (A)

When ultrasound travels through tissue, its intensity decreases as energy is removed from the forward beam. The three main ways this happens are absorption, scattering, and reflection. Absorption converts acoustic energy into heat within the tissue, with more loss at higher frequencies. Scattering sends energy in many directions away from the forward path, so less energy continues in the same direction toward the transducer. Reflection occurs at boundaries where there’s a mismatch in acoustic impedance; part of the incident energy is bounced back toward the transducer, reducing the energy that continues forward. Together, these processes reduce the forward-propagating energy and are the standard components described for attenuation.

Options that include refraction or diffraction don’t represent the primary attenuation mechanisms, and referring to transmission describes energy that passes through a boundary rather than being attenuated.