When you select harmonic imaging, which artifact is less likely to be observed?

• A. Refraction
• B. Shadowing
• C. Ring-down
• D. Grating lobes

Answer: (D)

Harmonic imaging works by using the tissue-generated second harmonic frequency and filtering to that harmonic, which narrows the effective beam and reduces energy from off-axis sources. That off-axis energy is what creates grating-lobe artifacts in conventional imaging, so by suppressing those off-axis contributions, grating-lobe artifacts become much less likely when harmonic imaging is used. Refraction arises from speed differences that bend the sound path and isn’t specifically mitigated by switching to harmonic frequencies. Shadowing comes from deep attenuation and remains a limitation regardless of harmonic imaging. Ring-down is tied to resonant signals from gas or metal interfaces and isn’t directly addressed by tissue harmonics. So the artifact least likely with harmonic imaging is grating lobes.