Interference patterns of the reflected waves cause which ultrasound imaging phenomenon?

• A. Acoustic speckle
• B. Acoustic enhancement
• C. Rarefaction
• D. Volume averaging

Answer: (A)

Acoustic speckle arises from interference of many tiny reflections within the tissue. In ultrasound, the sound wave encounters countless microscopic scatterers, each reflecting a portion of the wave with slightly different travel times and phases. The receiver sums all these echoes coherently, so the waves add together constructively in some places and destructively in others. This random pattern of bright and dark spots across the image is the granular texture called speckle. It’s a fundamental artifact of the coherent imaging process and can be reduced with filtering or imaging techniques, though it also contains information about tissue microstructure.

Acoustic enhancement is caused by reduced attenuation behind a fluid-filled region, making deeper tissues appear brighter. Rarefaction is a phase part of the wave, not a separate imaging pattern. Volume averaging (partial volume effect) comes from limited spatial resolution blurring signals from different structures within a voxel, not from interference.