Ultrasound Physics Flashcards
Low FPS and Low Q gives what?
Better Axial resolution
Time for a soundwave to return from reflector?1 cm deep?
13 microseconds
What structure is unlikely to reflect sound waves?
Urinary bladder contents
If intensity is attenuated -30 db, what is the percent intensity now?
relative intensity = 10log(I2/I1)
- 30 = 10 log (I2/I1)
- 3 = log (I2/I1)
10^-3 = I2/I1
I2 = 0.001 I1
Which is 0.1%
For US safety you should follow?
ALARA (As Low As Reasonably Possible)
lateral resolution is improved
On one of the answers as I recall?
What type of flow is normal in vessels?
Blunt.
Is laminar flow normal in most vessels?
No
What is duplex imaging?
combination of 2d B mode and pulsed doppler acquisition
What does high Q mean?
Not sure, but I think answer is increased bandwidth?
Phased array US is used for?
Cranial US
Matching layer refers to?
The weird answer with the acoustic step down. Talks about intratissue blah blah but mentions acoustic step down.
Damping results in?
better axial resolution? Also higher bandwidth shorter pulses more frequencies lower quality factor lower intensity
Is “change operating frequency an answer”?
Yes, to something.
speed of sound is highest in?
Bone
Sound speed depends on?
Stiffness and density
Are there bioeffects at 100W/whatever?
Yes. He is being tricky dick with units. Slide says no bio effects under 100 milliwatts/whatever
What is Q factor = to?
Q factor = operating frequency/bandwidth
MI refers to?
Cavitation
Highest doppler shift vessel will be?
Aorta
Harmonic echoes detected at 3mhz?
6 mhz
When fluid moving towards transducer it is colored?
Red
To avoid aliasing do what?
Increase PRF to adjust velocity scale to wider range
Harmonic imaging improves what resolution?
Lateral and elevational
What is power doppler good for?
Sensitive to slow flow
Focusing improves what?
Axial resolution
Multiple focal zone US takes longer, why?
Multiple pulses used to generate one line
How do you adjust for depth of field?
With time gain compensation
Does damping increase bandwidth?
yes
1/2 value layer is the amount need to attenuate beam by what?
3 db (50% reduction)
What does spatial pulse length determine?
Axial resolution
What does spatial pulse length determine?
Axial resolution
Cystic structures demonstrate what artifact?
Posterior acoustic enhancement
The duodenum he shows has what artifact?
reverberation
Answer to question about which angle and frequency give highest doppler shift?
10 mhz and parallel
Is frequency likely to change between tissues?
No, is determined by the sound source
where as speed and wavelength are influenced by the medium
Quality factor = ?
Operating frequency/bandwidth
Power doppler relies on _______ _______ rather than doppler frequency signal?
return doppler signal strength
Disadvantage of harmonic imaging?
Degrades axial resolution
Tissue heating is of greates concern in what modality of US?
Spectral Doppler
