What is the near field also known as in ultrasound imaging?

In ultrasound imaging, the near field is also known as the Fresnel Zone. This part of the ultrasound field is crucial for clinicians to understand as it represents the area close to the transducer where constructive and destructive interference of ultrasound waves occurs, creating a variety of image qualities.

The Fresnel Zone is characterized by the initial propagation of ultrasound waves, which spreads out as it moves away from the transducer but is less uniform and somewhat turbulent compared to the far field. Understanding this zone helps sonographers ensure high-quality imaging, particularly for structures that are located near the surface being examined. In this zone, the beam is more directed and has a better resolution, which is essential for accurate diagnostic work.

The other terms such as the Fraunhofer Zone refer to the area further away from the transducer where the ultrasound beam starts to diverge and image quality may decrease. The focal zone is specifically the area where the ultrasound beam is most focused, achieving the best spatial resolution, while the imaging zone may encompass both near field and far field zones for broader imaging purposes. Thus, referring to the near field as the Fresnel Zone is accurate and reflects significant principles of ultrasound physics.