Radiology · Fundamentals of X-Ray, CT, MRI and USG (Physics, Basics)

In ultrasound, which artifact is responsible for the bright reflections seen behind gallstones, producing posterior acoustic shadowing?

A Reverberation artifact
B Acoustic enhancement (posterior enhancement)
C Reflection and refraction at a highly attenuating interface ✓
D Side-lobe artifact

Correct answer: C. Reflection and refraction at a highly attenuating interface

Explanation

Posterior acoustic shadowing behind gallstones results from strong reflection and absorption at the highly attenuating calcified stone surface — the stone reflects most of the incident ultrasound, leaving a 'shadow' (zone of reduced signal) deep to it. This clean acoustic shadow is a key diagnostic feature of cholelithiasis. Posterior acoustic enhancement (increased echogenicity behind a cyst) results from increased through-transmission past low-attenuating fluid. Reverberation produces multiple equidistant parallel echoes. Side-lobe artifacts produce spurious echoes within cysts.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.

In ultrasound, which artifact is responsible for the bright reflections seen behind gallstones, producing posterior acoustic shadowing?

Explanation

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