Which term refers to the area where the sound beam is most concentrated at the focus?

• A. Focal Zone
• B. Elevation Resolution
• C. Detail Resolution
• D. Diffraction

Answer: (A)

The focal zone describes the region around the focus where the beam remains most concentrated and narrow, with the highest intensity. This is where lateral resolution is best because the beam width is smallest in the lateral direction, allowing finer detail to be seen at that depth. As you move away from the focal point, the beam broadens and resolution diminishes, which is why imaging is sharpest within this zone.

Elevation resolution, by contrast, relates to the slice thickness in the elevation plane and not to the focused region of maximum beam concentration. Diffraction is the general wave phenomenon that explains how sound waves bend and spread through an aperture, enabling focusing, but it’s not the name for the region of maximum concentration itself. The term used here for the region of maximum beam concentration at the focus is the focal zone.