Which choice best describes how beam width affects spatial resolution?

• A. Increasing beam width improves spatial resolution
• B. Reducing beam width improves spatial resolution
• C. Beam width has no effect on spatial resolution
• D. Beam width only affects color imaging

Answer: (B)

Narrower beam width improves spatial resolution because it confines the ultrasound energy to a smaller lateral area. When the beam is thin, two closely spaced structures cast echoes from distinct parts of the image, allowing the system to distinguish them as separate objects. If the beam is wide, the energy covers a larger region, causing signals from adjacent structures to blur together and degrade lateral resolution. It’s useful to remember that axial resolution depends mainly on pulse length, not beam width, and focusing can sharpen the beam in the region of interest, though the beam widens outside the focal zone. Color imaging is not determined by beam width.