Which term describes the distance from the transducer to the focus?

Which term describes the distance from the transducer to the focus?

• A. End of near zone
• B. Near zone length
• C. Far zone distance
• D. Focal depth

Answer: (D)

Focal depth is the distance from the transducer to the focus. The focus is the point where the ultrasound beam is most tightly focused, giving the best lateral resolution. By definition, measuring from the transducer face to that narrowest, most concentrated point gives the focal depth. The end of the near field is the boundary where the beam finishes converging, and the near zone length is that distance to the end of the converging region; the far zone distance refers to how far the beam travels in the divergent, far field. These terms describe other parts of the beam path, whereas the distance to the focus itself is defined as focal depth.

Focal depth is the distance from the transducer to the focus. The focus is the point where the ultrasound beam is most tightly focused, giving the best lateral resolution. By definition, measuring from the transducer face to that narrowest, most concentrated point gives the focal depth. The end of the near field is the boundary where the beam finishes converging, and the near zone length is that distance to the end of the converging region; the far zone distance refers to how far the beam travels in the divergent, far field. These terms describe other parts of the beam path, whereas the distance to the focus itself is defined as focal depth.