What is the role of tissue harmonic imaging?

• A. Increases frame rate
• B. Reduces speckle and improves contrast by using tissue harmonics
• C. Increases penetration depth
• D. Increases image noise

Answer: (B)

Tissue harmonic imaging relies on the tissue itself generating harmonic frequencies as the ultrasound wave propagates. Instead of using only the transmitted (fundamental) frequency, the image is formed from the second-harmonic signal that tissue produces. This harmonic signal tends to come from deeper in the path and has different beam properties, which helps reduce clutter and distortion that can blur edges.

Because these harmonics have a higher frequency content, the system that receives them benefits from a tighter, cleaner point spread, which translates into crisper borders and better tissue contrast. The net effect is a cleaner image with less speckle noise and improved conspicuity of structures.

It doesn’t increase depth penetration—harmonics attenuate more quickly than the fundamental—nor does it primarily raise frame rate or increase noise. So the main role is using tissue-generated harmonics to reduce speckle and improve contrast.