What artifact has a grainy appearance and is caused by the interference effects of scattered sound?

• A. Spackle
• B. Speckle
• C. Reverberation
• D. Slice thickness

Answer: (B)

Speckle is the granular texture seen on ultrasound images, produced when ultrasound waves scatter off many small tissue structures within a single resolution cell and the echoes combine with varying phases. This coherent interference causes random constructive and destructive patterns, giving that grainy look. It’s a fundamental imaging artifact tied to tissue microstructure and the physics of coherent ultrasound, not due to a wrong setting or a flaw in the machine. This grainy pattern helps distinguish speckle from other phenomena: reverberation shows as multiple evenly spaced parallel lines from repeated reflections between strong interfaces, slice thickness blurs edges due to partial volume effects, and spackle is unrelated. Speckle can be reduced somewhat by techniques like spatial or frequency compounding, but it remains an intrinsic part of ultrasound images.