Tissue harmonic imaging improves angular resolution by what mechanism?

• A. By increasing frame rate
• B. By yielding a narrower beam due to reduced near-field clutter
• C. By widening the beam for a broader field of view
• D. By enhancing color Doppler sensitivity

Answer: (B)

Angular resolution depends on how narrow the ultrasound beam is in the plane of imaging. Tissue harmonic imaging works by detecting the harmonics generated as the wave travels through tissue, and it tends to filter out the strong near-field clutter from the fundamental signal. This reduction in near-field artifacts allows the received harmonic image to be formed with a tighter, more focused beam. A narrower effective beam translates directly into better lateral (angular) resolution, giving sharper side-to-side detail.

The other ideas don’t explain why the angular resolution would improve: increasing frame rate changes temporal sampling, not the beamwidth; widening the beam would actually degrade resolution; and color Doppler sensitivity is about flow visualization, not the beam geometry driving angular resolution.