Ultrasound Beams Flashcards
What is the Near Zone?
The length of the beam from the transducer to the focus point. Also known as the Fresnel Zone
Is Near Zone Length and Near Zone the same thing?
No, NZL measures the distance from the transducer to the focus point while Near Zone is the region only.
Where is the focal point located?
It is 1/2 the original beam diameter.
What is another name for the Far Zone?
Fraunhofer zone (region).
Where is the Far Zone?
It is the region from the focus point to the original beam diameter
What does the Far Zone length measure?
The distance from the focus point to the original beam diameter
Does NZL=FZL
Yes. The length of the near zone to the focal point is the same as the far zone length.
How do you calculate NZL?
NZL=D^2/(4 * wavelength)
Where is the best image detail in a sound beam?
In the focal zone. The narrowest point of the beam is able to get between tightly spaced objects. Better lateral resolution
The focal length depends on what two factors?
Crystal diameter and transducer frequency.
Do focal length and crystal length have a direct relationship?
Yes. When the crystal diameter is larger, the focal zone is longer.
Do Focal length and transducer length have a direct relationship?
Yes. When the frequency is increased, the focal length also increases
Shallow imaging utilizes what type of crystal diameter and frequency?
Shallow imaging uses a high frequency probe with a small crystal diameter.
Beam divergence depends on what two factors?
The diameter of the crystal and frequency of the transducer
Does beam divergence and crystal diameter have a direct or inverse relationship?
Inverse. As the diameter of the crystal gets larger, the beam diverges less
