In which zone does beam divergence occur?

Beam divergence occurs in the Fraunhofer zone, which is more commonly referred to as the far field of an ultrasound beam. As the ultrasound beam travels away from the transducer, it begins to spread out and diverge. This phenomenon is significant because the degree of divergence affects the resolution and the quality of the images obtained during an ultrasound examination.

In the Fraunhofer zone, the beam has already passed through the near zone, where it is more focused and collimated. In contrast, the near zone is where the beam is still converging, while the Fresnel zone encompasses the area between the near and far zones, where the beam transitions from being collimated to diverging. The spatial zone is not a recognized term in the context of ultrasound beam characteristics. Therefore, understanding that beam divergence is a characteristic of the Fraunhofer zone aids in comprehending how ultrasound beams propagate and are influenced by distance from the transducer.