Attenuation is determined by which factors?

• A. Wavelength and speed
• B. Path length and frequency
• C. Beam angle and impedance
• D. Temperature and viscosity

Answer: (B)

Attenuation is the loss of ultrasound intensity as it travels through tissue, and the main factors that govern it are how far the sound must travel (path length) and the frequency of the sound. Higher frequency waves are absorbed and scattered more readily by tissue, so they lose more energy per unit distance. Consequently, longer travel paths accumulate more attenuation. Wavelength and speed are related but don’t set how much energy is lost along the path—the loss comes from absorption and scattering, which scale with frequency. Beam angle and impedance describe reflections at boundaries, not the gradual attenuation through a uniform medium. Temperature and viscosity can influence tissue properties slightly, but they aren’t the primary determinants of attenuation in standard ultrasound practice.