The distance over which the ultrasound beam remains relatively narrow and maintains good lateral resolution is called which term?

The distance over which the ultrasound beam remains relatively narrow and maintains good lateral resolution is called which term?

• A. Far field
• B. Slice thickness
• C. Near zone length
• D. Echo range

Answer: (C)

This asks about how far the ultrasound beam stays narrow as it travels. The region directly in front of the transducer where the beam remains relatively narrow and maintains good lateral resolution is the near field, also called the Fresnel zone. The near field length is the distance from the transducer to the point where the beam starts to spread noticeably. Within this zone, the beam width is small, so lateral resolution is high. After this distance, the beam enters the far field and begins to diverge due to diffraction, causing the lateral resolution to worsen. The near field length depends on transducer diameter and wavelength (larger aperture or shorter wavelength increases the near field length). The far field is the region where the beam widens, slice thickness relates to the imaging plane’s thickness (elevation resolution), and echo range isn’t the standard term for this concept.

This asks about how far the ultrasound beam stays narrow as it travels. The region directly in front of the transducer where the beam remains relatively narrow and maintains good lateral resolution is the near field, also called the Fresnel zone. The near field length is the distance from the transducer to the point where the beam starts to spread noticeably. Within this zone, the beam width is small, so lateral resolution is high. After this distance, the beam enters the far field and begins to diverge due to diffraction, causing the lateral resolution to worsen. The near field length depends on transducer diameter and wavelength (larger aperture or shorter wavelength increases the near field length). The far field is the region where the beam widens, slice thickness relates to the imaging plane’s thickness (elevation resolution), and echo range isn’t the standard term for this concept.