Which region starts at the focus and extends deeper?

Which region starts at the focus and extends deeper?

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

Answer: (A)

In ultrasound, the beam travels through different zones along depth. The tightest, most focused part of the beam is at the focal point. Beyond that point, as the wave continues deeper into tissue, the beam begins to spread out. That spreading region is the far zone—the part of the beam after the focus where divergence occurs. So the region that starts at the focus and extends deeper is the far zone. The area right around the focus is the focal zone (where the beam width is smallest), the region closer to the transducer is the near field, and the area between the near field and far field is the transition zone.

In ultrasound, the beam travels through different zones along depth. The tightest, most focused part of the beam is at the focal point. Beyond that point, as the wave continues deeper into tissue, the beam begins to spread out. That spreading region is the far zone—the part of the beam after the focus where divergence occurs. So the region that starts at the focus and extends deeper is the far zone. The area right around the focus is the focal zone (where the beam width is smallest), the region closer to the transducer is the near field, and the area between the near field and far field is the transition zone.