Lateral resolution is determined by the _________.

• A. Width of the sound beam
• B. Depth of tissue
• C. Pulse duration
• D. Frequency of emitted sound

Answer: (A)

Lateral resolution is about distinguishing two structures that lie side by side across the ultrasound beam. The key factor that sets how close those two points can be while still being seen as separate is the width of the sound beam itself. A narrower beam creates a smaller footprint on each imaging plane, so two echoes that are close laterally produce distinct signals, giving better lateral resolution. The beam width is smallest at the focus, so focusing improves lateral resolution there.

Depth of tissue affects how far the sound can travel and how the signal attenuates, not how finely two points can be resolved side by side. Pulse duration governs axial resolution along the beam path, not lateral resolution. Frequency helps with both resolution and penetration, but the direct determinant of lateral resolution is the beam width.