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69 Cards in this Set

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The following factors relate to what type of doppler?
- range resolution
- sample volume
- limited maximum velocity (Nyquist)
- aliasing
Pulsed Doppler
The following factors relate to what type of doppler?
- range ambiguity
- region of overlap
- unlimited maximum velocity
- no aliasing
CW Doppler
The following factors relate to what type of transducer?
- at least one crystal
- damped PZT
- low Q-factor
- wide bandwidth
- lower sensitivity
Pulsed Doppler Transducer
The following factors relate to what type of transducer?
- at least two crystals
- undamped PZT
- high Q-factor
- narrow bandwidth
- higher sensitivity
CW Doppler Transducer
The following factors relate to what general type of modality?
- normal incidence
- higher frequency
- pulsed wave only
- minimum of 1 crystal
Imaging
The following factors relate to what general type of modality?
- 0/180 degrees
- lower frequency
- pulsed or CW
- min of 1 (pulsed) or 2 (CW) crystals
Doppler
In this modality, velocity information is coded into colors and superimposed on a 2D grayscale, anatomic image
Color Flow Doppler
Is spectral doppler considered qualitative or quantitative?
Quantitative
Is color flow doppler considered qualitative or quantitative?
Qualitative
Since color flow doppler is based on ___ techniques, it has the same advantages (___) and disadvantage (___)
Pulsed Wave
+ Range Resolution/Specificity
- Aliasing
What type of velocities does color doppler report?
Average/Mean Velocities
What does RABT stand for?
Red Away Blue Towards
What does BART stand for?
Blue Away, Red Towards
What type of velocities does PW and CW doppler report?
Peak Velocities
In color doppler, the color represents what?
Flow Direction
What does black represent in color doppler?
No doppler shift
Colors above the black stripe represent blood cells moving in what direction?
Toward the Transducer
Colors below the black stripe represent blood cells moving in what direction?
Away from the Transducer
Flow toward the transducer is what kind of doppler shift?
Positive Doppler Shift
Flow away from the transducer is what kind of doppler shift?
Negative Doppler Shift
Colors closer to the black stripe represent what?
Slower speeds
Colors farther away from the black stripe represent what?
Faster speeds
In addition to direction and velocity, what additional information does variance mode offer?
Laminar vs Turbulent Flow
In variance mode, what do the colors on the left side represent?
Laminar Flow
In variance mode, what do the colors on the right side represent?
Turbulent Flow
In color doppler, multiple pulses are used to accurately determine blood velocities. What are these multiple pulses called?
Packets
Ensembles
The following advantages apply to what type of packets/ensembles?
- more accurate velocity measurements
- more sensitive to low flow
Larger Packets
Longer Ensemble Lengths
The following disadvantages apply to what type of packets/ensembles?
- more time needed to acquire data
- reduced frame rate
- decreased temporal resolution
Larger Packets
Longer Ensemble Lengths
Flows detected at angles closer to 0 degrees will be ___ than those detected closer to 60 degrees
Brighter
This modality only identifies the presence of a doppler shift, not speed or direction
Power Doppler
Energy Mode
Color Angio
In this modality, the strength/amplitude of the reflected signal is processed, which is directly related to the number of moving blood cells
Power Doppler
Energy Mode
Color Angio
What are 3 advantages of power doppler?
1. increased sensitivity to low velocities
2. unaffected by doppler angles (unless 90 degrees exactly)
3. no aliasing
What are 3 disadvantages of power doppler?
1. no velocity or direction information
2. lower frame rates / temporal resolution
3. susceptible to motion / flash artifacts
In addition to moving blood, very low frequency doppler shifts may be produced by ___ or ___
Moving Anatomy
Pulsating Vessels
On spectral displays, low frequency doppler shift artifacts called what?
Clutter
On color displays, low frequency doppler shift artifacts are called what?
Ghosting
How is clutter or ghosting eliminated?
Wall Filter
These exclude low frequency doppler shifts around the baseline, but have no effect on higher doppler frequency shifts commonly created by blood cell motion
Wall Filters
This is a special form of mirror image artifact that only appears with spectral doppler; while the flow pattern appears identical above and below the baseline, the true pattern in unidirectional
Crosstalk
The following cause what type of artifact?
- doppler receiver gain too high
- incident angle near 90 degrees between the beam and the flow direction
Crosstalk
This is the tool that breaks up a complex signal into the individual velocities which make up the reflected doppler signal
Spectral Analysis
This doppler analysis tool is exceedingly accurate and displays all individual velocity components from the reflected signal; it is used with PW and CW doppler
FFT (Fast Fourier Transform)
Using FFT, a laminar flow will produce what in the display?
Spectral Window
Using FFT, a turbulent flow will produce what in the display?
Spectral Broadening
When the spectral window is filled in, this is called what? and results from what?
Spectral Broadening
Turbulent Flow
This doppler analysis tool is less accurate but substantially faster than FFT; it is used with color flow doppler
Autocorrelation
Correlation Function
Can a patient be so severely anemic that a doppler exam cannot be performed?
No
Is FFT quantitative or qualitative?
Quantitative
Is autocorrelation quantitative or qualitative?
Qualitative
This ratio is a quantitative, doppler-derived measurement of the vascular resistance of a segment of the arterial system. It requires min/max velocities
Resistivity Index (RI)
This ratio is a quantitative, doppler-derived measurement of the vascular resistance of a segment of the arterial system. It requires min/mean/max velocities
Pulsatility Index (PI)
The following are advantages of what?
- based on mathematical measurements
- based on waveform shapes; unaffected by doppler angles
Resistivity Index (RI)
Pulsatility Index (PI)
The doppler effect is presented as a ___ when the source and the receiver are ___
Frequency Shift
Moving relative to each other
Starting from the same point, the sound source is moving east at 12 miles/hour and the receiver is moving west at 10 miles/hour. The doppler shift is ___
Negative
Starting from the same point, the receiver is moving west at 12 miles/hour and the source is moving west at 10 miles/hour. The doppler shift is ___
Negative
Doppler shift produces information about ___
Velocity
At what angle between the sound beam and the direction of motion will the doppler shift be at a maximum?
0/180 degrees
At what angle between the beam and the direction of motion will the doppler shift be a minimum?
90 degrees
What is the difference between speed and velocity?
Speed = magnitude
Velocity = magnitude & direction
What is the current method of processing doppler signals?
FFT for spectral doppler
Autocorrelation for color doppler
What is the typical range of doppler shift found in diagnostic imaging?
20 Hz - 20 kHz (in the audible range)
The phenomenon where high velocities appear negative is called what?
Aliasing
The frequency at which aliasing occurs is called what?
Nyquist Limit
The area of interrogation in a pulsed doppler exam is called what?
Sample Volume
T/F: the higher the emitted frequency, the more likely a pulsed wave signal is to alias
T
T/F: shallower sample volumes result in more aliasing
F
T/F: only pulsed wave doppler exams have a sample volume
T
An 8 MHz transducer with a PRF of 5,000 Hz is imaging to a depth of 7 cm. What is the Nyquist frequency?
A. 4 MHz
B. 3.5 Hz
C. 2.2 kHz
D. 2.5 dB
E. 5 kHz
C
An 8 MHz transducer with a PRF of 5,000 Hz measures a doppler shift of 7 kHz. The study is repeated with a 4 MHz transducer. What doppler shift will be measured?
A. 4 MHz
B. 3.5 Hz
C. 4 kHz
D. 3.5 dB
E. 3,500 Hz
E