What is the term for the depth region associated with a focal point in annular arrays?

What is the term for the depth region associated with a focal point in annular arrays?

• A. Focal length
• B. Focal depth
• C. Focusing range
• D. Image depth

Answer: (B)

The focal depth describes the depth region where the ultrasound beam is focused in an annular array. By driving the concentric rings with appropriate delays, the beam converges to a tight spot at a chosen depth, and the surrounding axis region where the beam remains concentrated is the focal zone. The distance from the transducer to that focus defines the focal depth. This distinguishes it from focal length (the distance to the focus itself), focusing range (a broader adjustable span), or image depth (a general imaging depth). So the term that matches the depth region tied to the focal point is focal depth.

The focal depth describes the depth region where the ultrasound beam is focused in an annular array. By driving the concentric rings with appropriate delays, the beam converges to a tight spot at a chosen depth, and the surrounding axis region where the beam remains concentrated is the focal zone. The distance from the transducer to that focus defines the focal depth. This distinguishes it from focal length (the distance to the focus itself), focusing range (a broader adjustable span), or image depth (a general imaging depth). So the term that matches the depth region tied to the focal point is focal depth.