High Yield PTEeXAM Review Part 6-8 Flashcards
What is a normal DF range?
- 2 - 0.5%
i. e. Listening 99.8% of time
What is duty factor determined by?
Sound source only
What is duty factor inversely related to?
Depth
What is the Duty Factor % equation?
Pulse Duration* / *Pulse Repetition Period
How does the Pulse repetition frequency change with shallow vs. deep images?
Shallow = Higher PRF
Deep = Lower PRF
How does duty factor change with depth?
Shallow = Higher DF Deeper = Lower DF
What is the typical value of a pulse duration?
0.5 - 3.0 microseconds
What is the typical pulse repetition period?
0.1 - 1.0 ms
What is the typical pulse repetition frequency?
1 - 10 kHz
What is the typical spatial pulse length?
0.1 - 1.0 mm
During PWD echo, the frequency of the emitted beam is determined by what two things?
- Thickness of piezoelectric crystals
- Speed of propagation of sound in the crystals
What is the equation for resonant frequency?
Velocity of sound in crystal* / [*2 * thickness of the crystal]
Which ASD is more common:
Superior* sinus venosus VSD or an *inferior sinus venousus VSD?
superior = More common
What is a superior sinus venousus ASD associated with?
Anomalous Venous Drainage of the RUPV
What is a inferior sinus venousus ASD associated with?
Anomalous pulmonary venous drainage of a scimitar vein
Scimitar syndrome
Drains from hypoplastic RLL of the lung
Aortopulmonary collaterals
What 3 things does Scimitar syndrome have?
- Inferior Sinus venous ASD
- RLL hypoplastic lung with scimitar vein draining into the IVC
- Aortopulmonary collaterals going to RLL of the lung
What is ostium primum ASD associataed with?
Trisomy 21
Near AV valves (Cleft leaflets)
- Septal TV
- Anterior MV
What is a partial AV canal?
Primum ASD with No VSD
What is a transitional AV canal?
Primum ASD with restrictive inlet VSD
What is a complete AV canal?
Primum ASD + Non-restrictive inlet VSD
An ostium secundum ASD is a defect in what structure?
Defect in septum primum (Area of fossa ovalis)
What is ostium secundum ASD associated with?
Mitral valve prolapse
Transmitral Flow Propagation Velocity:
load dependent or load independent?
Load dependent
What does the backing material of the echo probe function to do?
Shortens the pulse duration
The matching layer is how thick in comparison to the wavelength?
About 1/4 length of the wavelength
The piezoelectric crystals are how thick compared to the wavelength?
About 1/2 the wavelength
What is the benefit of a short pulse duration?
Improved axial resolution
Why? Axial resolution = 1/2 * Spatial Pulse Length
How does backing material affect bandwidth?
Increases bandwidth
How does increased bandwidth affect Q factor?
Q = RF / Bandwidth
How does frequency affect penetration?
Increased frequency = Increased penetration (More attenuation)