Which region yields more accurate images due to beam focus?

Which region yields more accurate images due to beam focus?

• A. Focal zone
• B. Far field
• C. Near field
• D. Transition zone

Answer: (A)

Beam focusing concentrates ultrasound energy into a narrow cross-section at a specific depth. The region around that depth, where the beam width is smallest and the intensity is highest, is the focal zone. Because lateral resolution—the ability to distinguish closely spaced structures—depends on how narrow the beam is, images produced in the focal zone are sharper and more accurate. In the near field, the beam is still converging and not at its minimum width, so resolution isn’t as high. In the far field, the beam widens again, reducing lateral resolution. This is why the focal zone yields the most accurate images when beam focus is used.

Beam focusing concentrates ultrasound energy into a narrow cross-section at a specific depth. The region around that depth, where the beam width is smallest and the intensity is highest, is the focal zone. Because lateral resolution—the ability to distinguish closely spaced structures—depends on how narrow the beam is, images produced in the focal zone are sharper and more accurate. In the near field, the beam is still converging and not at its minimum width, so resolution isn’t as high. In the far field, the beam widens again, reducing lateral resolution. This is why the focal zone yields the most accurate images when beam focus is used.