In diagnostic ultrasound, which pair describes the related quantities for changes in signal strength?

• A. Weakening and Amplification
• B. Frequency and Wavelength
• C. Phase and Density
• D. Velocity and Impedance

Answer: (A)

The main idea is about how the strength of the ultrasound signal changes as it travels and is processed. As the sound wave moves through tissue, its amplitude can diminish—this is attenuation, or a weakening of the signal. Conversely, the system can increase the displayed signal strength through amplification (gain). So the paired terms that describe changes in signal strength—both decreases and increases—are weakening and amplification.

The other pairs don’t capture changes in signal strength. Frequency and wavelength describe the wave’s cycle rate and distance per cycle, not how strong the signal is. Phase and density relate to the wave’s timing and the tissue’s properties, not amplitude changes. Velocity and impedance involve how fast the wave travels and how it meets different media, not directly how the signal’s strength changes.