Doppler & Hemodynamics Flashcards
When imaging blood flow with a low flow state, what setting may optimize Doppler visualization?
- higher PRF, lower Doppler gain
- lower PRF, lower Doppler gain
- higher PRF, higher Doppler gain
- lower PRF, higher Doppler gain
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When imaging the portal vein, a sonographer obtains the following PW Doppler waveform. What adjustment needs to be made to improve this waveform?
decease PW gain
What would be the optimal maximum Doppler scale setting a sonographer should use to image blood flowing at 20 cm/sec?
- 20cm/sec
- 10cm/sec
- 30cm/sec
- 90cm/sec
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Which condition causes Rayleigh scattering to occur?
red blood cells are smaller than the wavelength of the sound beam
What is a true statement that applies to the areas being pointed out by the arrows in this color Doppler image?
- These are areas of low signal detection
- These areas have low velocities
- Na
- These areas have low pressure
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What is true of the flow direction for the posterior vessel shown in this Sagittal color Doppler image?
flow is moving toward the beam
The most inaccurate Doppler shift occurs at which angle?
90 degree
As the angle between the transducer and flow decreases, what happens to the Doppler shift?
it increases
What may result if Doppler gain settings are too high?
Over measurement of flow velocities
What frequency setting will have the greatest risk of aliasing?
12MHz
Aliasing of the Doppler spectrum occurs whenever the frequency shift exceeds which value?
½ PRF = Nyquist limit
Which term is used to describe a Doppler instrument that can distinguish between positive and negative Doppler shifts?
- Fast Fourier Transform
- Duplex Imaging
- Bidirectional System
- Range Gating
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Use of frequency bins for signal processing of the PW Doppler signal is accomplished by?
FFT (Fast Fourier Transform)
What enables depth selectivity and a small sample volume?
range gating
When would a sonographer see a widening of the Doppler spectrum due to a broader range of flow speeds and directions?
- when there is spectral broadening
- when there is disturbed flow
- when there is turbulent flow
- all of the above
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Which description best fits pulsed Doppler systems?
- they have a large sample volume
- they are not subject to aliasing
- they sample specific locations
- hey allow for unlimited velocities
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When using PW Doppler, what are longer sample volume gate lengths used for?
- spectral analysis of center flow
- increased transducer frequency
- increased flow velocities
- locating deep or minimal flow patterns
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What is present in this PW Doppler waveform?
spectral broadening
Which of the following is not seen in CW Doppler when compared to PW Doppler?
- flow direction
- aliasing artifact
- stenosis detection
- NA
2
The velocity profile is relatively constant across the entire vessel and seen at the entrance of vessel is known as
plug flow
Which term applies to the physical principles associated with the study of blood circulation?
hemodynamics
Within the circulatory system, what is the relationship between pressure differences and flow rate?
directly related
Which law of physics states that pressure will drop in areas of high flow velocity?
Bernoulli’s Law
Frictional losses of energy during blood flow occur due to which factor?
- sliding of blood layers
- increased resistance
- increased vessel length
- all of the above
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