Tissue harmonic imaging helps reduce near-field clutter and improve angular resolution by which mechanism?

• A. It increases near-field clutter and broadens the beam
• B. It propagates with less near-field clutter and yields a narrower effective beam, improving resolution
• C. It reduces penetration depth
• D. It has no effect on angular resolution

Answer: (B)

Tissue harmonic imaging works by relying on nonlinear propagation in tissue to generate a second-harmonic wave, which is then received at twice the transmitted frequency. Because this harmonic signal is produced inside the tissue rather than at the transducer surface, the image is less contaminated by near-field clutter from the transducer and superficial structures. The harmonic signal also has a higher frequency, which means a shorter wavelength and a narrower effective beam. A tighter beam reduces off-axis energy and improves angular (lateral) resolution. In short, generating harmonics inside the tissue reduces near-field clutter and yields a narrower, more focused beam, leading to better resolution.