Which statement describes how lateral resolution of a tightly curved array changes with depth?

• A. It improves
• B. It stays the same
• C. It degrades with depth
• D. It becomes unpredictable

Answer: (C)

Lateral resolution depends on how wide the ultrasound beam is in the sideways direction. A tightly curved array focuses the beam so it’s narrow at a specific depth (the focal point), giving good lateral resolution there. As you go deeper beyond that focal depth, the beam spreads out due to diffraction and the curved aperture can’t keep it narrowly focused. The beamwidth increases, so the ability to distinguish two side-by-side structures worsens. Therefore, lateral resolution degrades with depth. This behavior is a predictable result of diffraction and focusing physics, not something that stays the same, improves, or is unpredictable.