Week 8 Sound Beams Flashcards
Sound Beams
What is the anatomy of a sound beam?
1.Focus
2. Near zone
3. Focal Length/ Near zone Length
4. Far zone
5. Focal Zone
Where is the focus located?
at the narrowest part of the beam.
What shape are sound beams?
Bowtie shape
Where is the near zone located?
It is the region from the transducer to the focus.
What are other names for the near zone?
- Near field
- Fresnel zone
What are other names for the Focal Length?
focal depth or near zone length.
What is focal length?
is the distance from the transducer to the focus.
What are other names for Far zone
- Far Field
- Fraunhofer zone
What is the Far zone?
Is the region that starts at the focus and extends deeper.
What happens within the far zone?
the beam diverges and spreads out.
What is the focal zone?
region around the focus where the beam is relatively narrow.
Half of the focal zone is located in the near field and the other half is located in the far field.
Where does superior image detail occur?
The Focal zone.
What is another name for the area directly after the transducer?
Aperature
At the transducer…..
Beam diameter equals the transducer diameter.
At the focus……
beam diameter is 1/2 the transducer diameter.
At 2 near zone lengths….
beam diameter equals transducer diameter.
Deeper than 2 near zone lengths….
beam diameter is wider than the transducer diameter.
If a transducer has a diameter of 12 mm, what is the diameter of the sound beam at depth of 8cm?
6 cm
The beam diameter is 1/2 the transducer diameter.
What characteristics determine the focal depth?
- transducer diameter
- Frequency of sound
How are transducer diameter and focal depth related?
They are DIRECTLY related.
How are frequency and focal depth related?
They are DIRECTLY related.
Characteristics of shallow focus
- smaller diameter PZT
- Lower frequency
Characteristics of deeper focus
- Larger diameter PZT
- Higher Frequency
Can a sonographer change the focal depth?
No, it is set by the ultrasound system.
