A small footprint transducer has a disadvantage related to elevational focusing. Which statement is true?

• A. It cannot be focused in the elevational direction
• B. The field of view in the far field is only one-quarter the diameter of the transducer
• C. The near-field lateral resolution is poor
• D. Resolution is degraded at large distances

Answer: (D)

Elevational focusing determines how thin the ultrasound slice is perpendicular to the imaging plane. A small footprint transducer has limited aperture in the elevational direction, so the beam is relatively thick out of the plane and can’t be focused very well there. As imaging depth increases, the elevational beam widens further, causing structures to blur together in the elevational dimension. This makes elevational resolution degrade with distance, which is the key disadvantage of a small footprint transducer.

That’s why the statement about resolution getting worse at larger distances best captures the effect of limited elevational focusing. The other options don’t describe this specific limitation: it isn’t necessarily true that elevational focus cannot be achieved at all, the far-field field of view isn’t the core issue here, and near-field lateral resolution isn’t the elevational problem being highlighted.