Which parameter has the least influence on lateral resolution?

• A. Frequency
• B. Focus depth
• C. Beam width
• D. Damping

Answer: (D)

Lateral resolution hinges on how wide the ultrasound beam is at the depth of interest. A narrower beam lets you separate two closely spaced reflectors side by side, so improving beam width—via higher frequency (shorter wavelength) and by focusing the beam or using a larger aperture—directly enhances lateral resolution. Damping, by contrast, mainly shapes the pulse’s duration and bandwidth, influencing how well you can resolve echoes along the beam axis (axial resolution) rather than how wide the beam is across the image. It doesn’t change the beam width as it propagates, so its effect on lateral resolution is minimal.