In tissue harmonic imaging, the receiver listens to which frequencies?

• A. Harmonic frequencies
• B. Fundamental frequencies
• C. All frequencies
• D. Only the transmitted frequency

Answer: (A)

Tissue harmonic imaging relies on the wave becoming nonlinear as it travels through tissue, which generates energy at multiples of the transmitted frequency. The ultrasound machine transmits at a fundamental frequency, but the receiver is set to pick up the higher-frequency components produced by the tissue—primarily the second harmonic. Receiving these harmonic frequencies yields a cleaner beam with fewer near-field artifacts and improved resolution and contrast.

So the receiver listens to harmonic frequencies rather than the original transmitted frequency. This is why the other options don’t fit: fundamental frequencies are what you started with and are typically suppressed in harmonic imaging; all frequencies would include unwanted components; and only the transmitted frequency would miss the tissue-generated harmonics that this imaging mode relies on.