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
4
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
3
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
4
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
3
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
4
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
3
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
4
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
4
Which term describes the quantity of blood moving through the vessel per unit of time?
volume flow rate
When distal arterioles vasoconstrict, what change to peripheral arterial blood flow may be detected?
higher resistance
Which variable has the greatest effect on vascular resistance?
diameter of the vessel lumen
Which is not a way in which venous blood from the legs is assisted in returning to the heart?
- Calf muscle pump
- inspiration
- expiration
- venous valves
3
When interpreting a spectral waveform, what does the presence of an open spectral window indicate?
laminar blood flow
Which of the following represents the resistive index?
- (PSV – EDV) / mean velocity
- (EDV – PSV) / PSV
- (PSV – EDV) / PSV
- (PSV – EDV) / EDV
3
(peak systolic velocity – end diastolic velocity)/peak systolic velocity
What is the term used for the pressure difference between the inside of a vein and the tissue outside?
transmural pressure
In an exercising patient, what is the response to peripheral resistance with arteriolar dilatation?
resistance decreases
If the Reynold’s number meets or exceeds this value, turbulent flow will occur.
2000
In a standing patient, where does the hydrostatic pressure measurement equal zero (0)?
near the heart
In the upper extremity proximal veins, what happens to venous flow during inspiration?
flow velocity increases and moves toward the heart
What happens as blood moves through an area of significant stenosis?
- potential energy decreases and kinetic energy increases
- potential energy increases and kinetic energy decreases
- both potential and kinetic energy increase
- both potential and kinetic energy decrease
1
What happens when blood flow is sampled in the center of laminar flow?
- velocities will be higher than if sampled toward the edges
- velocities will be lower than if sampled toward the edges
- velocities will be varied and cause spectral broadening
- velocities will be varied and show turbulent blood flow
1
Which of the following would have the greatest effect on volume blood flow in the circulatory system?
- vasoconstriction and vasodilation of the arterioles
- increased hydrostatic pressure in an erect patient
- a pathological condition of moderate to severe anemia
- a change in pressure gradient due to patient exercising
1
Which muscles help propel blood in lower extremity veins toward the heart?
soleus and gastrocnemius
When color Doppler is active, how many pulses per scan line are used to create underlying B-mode?
1-2
What method is used to steer the color beam with linear array TDR?
A mechanical
B electronic time delays
C electronic voltage variation
D apodization
E the color beam cannot be steered with a linear array transducer
B
The packet size in color Doppler refers to the number of:
A pulses per second
B sample volumes per scan lines
C scan lines per unit area
D pulse/listen cycles per acoustic scan line
E pulses required to create one frame
D
For color Doppler, each line of sight must be pulsed multiple times. The number of pulses per line is termed ensemble length, packet size, or shots per line. The number of pulses transmitted in one second is the pulse repetition frequency (PRF). How many of those pulses are fired on each scan line is the ensemble length.
You have obtained a color Doppler image of the common carotid artery. If the received ultrasound frequency is greater than the transmitted ultrasound frequency, which of the following would be correct?
A color encoding red, negative doppler shift
B color encoding blue, negative doppler shift
C color encoding red, positive doppler shift
D color encoding blue, positive doppler shift
E no doppler shift was detected
C
What would be the most likely result from increasing the transmit frequency of the color Doppler?
A improved sensititivy to slow flow
B improved penetration for imaging flow in deep tissues
C reduced flash artifact obsuring small vessel flow
D reduced color doppler aliasing
E improved visibility of complex flow hemodyanmics
A
What would be the most likely result from lowering the color threshold?
A increased visibility of small vessel flow in a parenchymal organ
B decreased flash aritfact
C incrased color writing on the vessel or cardiac wall
D incrased frame rate
E improved color penetration
Increased color writing on the vessel or cardiac wall.
During Doppler interrogation of the carotid artery, you detect spectral mirroring. Which of the following is a common cause of this artifact?
A doppler angle of interrogation near 90 degrees
B doppler angle of interrogation near 0 degrees
C wall filter set too high
D PRF set too low
E doppler gain set too low
A
The packet size in color Doppler refers to the number of?
Pulses per scan line. In B-mode imagine there is only one pulse per scan line. In color Doppler the number of pulses is increased between 3 and 32 per scan line
While evaluating the liver vasculature with color Doppler, you are unable to obtain signals from the deeper vessels. What should you do to enhance you ability to demonstrate deep flow?
Decrease the ultrasound frequency. Lower frequencies have increased penetration compared to high frequencies
Spectral analysis is used to?
Determine the distribution and magnitude of frequency shifts in the reflected Doppler signal
What parameter describes the axial length of the sampling volume for a color pixel?
Color gate
What display method below will help you to demonstrate flow turbulence with color Doppler?
A. Autocorrelation
B. Variance
C. Fast Fourier Analysis
D. Zero-crossing detection
E. Phased quadrature detection
Variance
What term describes the number of pulses that are used to determine the velocity along a color line of sight?
Packet size. This is also known as ensemble length or shots per line
What information does the z axis (brightness) on the Doppler shift provide
Amplitude
The Nyquist limit describes which of the following?
Sampling frequency needed to detect the Doppler signal
What would be the most likely result from increasing the transmit frequency of the color Doppler
Improve sensitivity to slow flow.
why?
Increasing the color Doppler transmit frequency will result in larger frequency shifts from slow flow and thus improve visibility.
It will decrease penetration to flow in vessels deep within the tissue. Changing the ultrasound frequency has negligible effect on frame rate.
What Doppler technique does provide range resolution?
Color Doppler
Power Doppler
Pulsed wave Doppler
Range resolution is the ability to determine the depth from which an echo has arrived. Fro range resolution, the sound must be pulsed so that the echo arrival time from each pulse can be measured.
When color Doppler is activated, in order to maintain frame rate, what may be reduced in the underlying B-Mode image?
The number of focal zones and the scan line density this results in lower lateral resolution
A common used process for determining direction in a Doppler instrument is?
Phase quadrature detection
What is the maximum velocity limit for a 3MHZ CW Doppler unit operating at a depth of 4 cm?
CW Doppler does not have an imposed maximum velocity unlike pulse wave Doppler
Increasing the wall filter will
Eliminate the high amplitude,low frequency shift signals caused by movement of the vessel wall.
What system control on doppler adjust the PRF
Spectral velocity scale
Which control optimization should you make to improve color Doppler sensitivity to slow flow?
A: Lower the packet size
B: Lower the transmitted ultrasound frequency in Doppler
C: Raise the PRF
D: Lower wall filter setting
E: Lower the threshold
D
Lower wall filter setting, to improve sensitivity to slow flow, the wall filter should be lowered. Increasing packet size may slightly improve sensitivity since it affects the signal to noise ratio. Increasing the doppler frequency will increase the frequency shift and improve sensitivity to flow
What aspect of the Doppler spectrum is color-encoded with color Doppler?
A: Amplitude
B: Frequency shift
C: Power
D: Velocity
E: Bandwidth
B
Which answer provides the best explanation for the reason that the frame rate decreases when color Doppler is activated?
A: The color Doppler pulse length is longer
B: There are more focal zones when color is active
C: The system memory resources are challenged
D: More pulses are fired on each line of sight
E: All of the above
D
More pulses are fired on each line of sight color Doppler requires 4-32 pulses for each scan line. B mode only requires 1 pulse for each focal on each scan line.
What controls affect the spatial resolution of the color image
Frequency and line density
According to the Doppler equation, for any given velocity, the frequency shift will increase by increasing the:
A: Doppler angle
B: Transmit frequency
C: Pulse length
D: Pulse repetition frequency
E: All of the above
B
The reynolds number increases with increasing
flow speed, diameter, density, visocity
A flow condition in which parallel streamlines of flow are present within a tube is termed:
A: Parabolic flow
B: Laminar flow
C: Aliased flow
D: Disturbed flow
E: Turbulent flow
B
If you increase the doppler transmit frequency during a doppler exam, what would be the expected result
The doppler frequency shift will also increase. Penetration is decreased with increase frequency.
Which of the following best describes the doppler frequency shift when you encounter high velocities within the vessel?
A) amplitude is increased
B) power is increased
C) frequency shift is increased
D) bandwidth is decreased
E) all of the above
Frequency shift is increased
The term ensembles length and dwell time are synonymous with
Packet size
At low velocity the red blood cells adhere to one another forming multicellular clumps. This is known as
Rouleaux formation. This is the stacking up of red blood cells that occur at low velocity and low shear rates. This produces a large echo and explains why the blood flow i s sometimes visible in these cases. When the velocity increases, the rouleaux breaks up and flow may no longer be visible.
You are most likely to see color bruit (spread widely) in which of the following cases
A) trickle flow within a small residual lumen
B) damped flow proximal to a high-grade stenosis
C) chronic vessel occlusion
D) turbulent flow distal to a high-grade stenosis
E) normal arterial flow
Turbulent flow distal to a high grade stenosis
Atherosclerosis begins within
intima
What doppler control removes frequencies below a given threshold resulting in a clean zero baseline
high pass filter
Which of the following should be regularly checked as a component of a quality control program
- System penetration
- Image uniformity
- Assurance of electric safety
- Distance measurement accuracy
The motion of particles in fluid sometimes observed in an intense ultrasound beam this is called
Acoustic streaming which is transported of fluid in the body
You have increased the packet size while using color doppler to evaluate flow. What negative result will occur from this action?
a) Decreased penetration
b) Decreased flow sensitivity
c) Decreased frame rate
d) Increased variance
e) Increased spectral broadening
c) Decreased frame rate
Spectral analysis is used to:
a) Determine the distribution and magnitude of frequency shifts in the reflected Doppler signal
b) Eliminate aliasing from the reflected signal
c) Color encode the Doppler frequency shift
d) Eliminate low- frequency shifts from the display
e) Determine the velocity of the moving reflector
a) Determine the distribution and magnitude of frequency shifts in the reflected Doppler signal
What limitation is present when you use high PRF Doppler?
a) Frame rate
b) Spatial resolution
c) Sensitivity to slow flow
d) Range resolution
e) Both C and D
e
The presence of the systolic spectral window of the Doppler waveform is affected by:
a) Sample volume size
b) Turbulent flow
c) Doppler gain
d) Position of the Doppler sample volume
e) All of the above
e
Which frequency setting will have the greatest risk for aliasing?
- 12 MHz
- 9 MHz
- 6 MHz
- 3 MHz
1
What technique is used to distinguish positive/negative Doppler shift?
The Doppler shift can be determined after performing the range Fourier transform (range FFT) first.
What is the “sample volume” or “gate”?What does it do?
it is the site where the Doppler signal originates
allows sonographer to determine the depth and location of blood flow sampling
analyzes complex vasculature (tumor flow or total vessel occlusion) and calculate total flow volumes
A large sample volume analyzes what?
Color persistence
- increase sensitivity
- pick up low flow signal by lingering
- slow down frame rate
You obtained this color Doppler image during a hepatic sonogram. There is no color signal detected within the portal vein. What can you do to improve sensitivity to slow flow?
Decrease pulse repetition frequency.
Which of the following is present in this Doppler spectral waveform? See also Color Plate 2
A. Spectral broadening
B. Narrow velocity range
C. Aliasing
D. Mirror imaging
E. Range ambiguity
A
The waveform shows fill-in of the spectral window. This loss of the window is indicative of spectral broadening. Spectral broadening is associated with turbulent flow.
While performing a Doppler study, the measurement of the Doppler angle of incidence was underestimated. What error will result from this mistake?
A. The frequency shift will be underestimated.
B. No Doppler frequency shift will be detected.
C. Mirror imaging of the Doppler spectrum will occur.
D. The velocity estimation will be inaccurate.
E. Aliasing of the Doppler spectrum will occu
D. The velocity estimation will be inaccurate.
The velocity estimation in Doppler ultrasound is based on measurement of the Doppler angle of incidence—the angle at which the Doppler beam intersects the blood flow. Because the blood flow is not directly visualized, the Doppler angle-correction cursor is aligned parallel to the walls of the vessel at the point of sampling. If this measurement is underestimated, the velocity of the flow will be underestimated. If this measurement is overestimated, the velocity of flow will be overestimated. Any time the angle-correction cursor is not adjusted parallel to the wall, the velocity estimation is in error.
A commonly used process for determining direction in a Doppler instrument is:
A. Zero-crossing detection
B. Autocorrelation
C. Phase quadrature detection
D. Range gating
E. Spectral analysis
C
When color Doppler is activated, in order to maintain frame rate, what may be reduced in the underlying B-mode image?
A. The number of focal zones
B. The scan line density
C. The frame averaging
D. A and B
E. B and C
D. A and B. To maintain an adequate frame rate in color Doppler, the B-mode image is compromised by reducing the number of focal zones to 1 or 2 and by reducing the scan line density, which results in lower lateral resolution.
. This Doppler waveform can be most accurately described as exhibiting:
A. Aliasing
B. Spectral broadening
C. Mirror image
D. Bidirectional flow
E. Saturation
A. Aliasing. With an aliased signal, the peak of the waveform is clipped off and appears on the opposite side of the baseline. It starts from the bottom of the image and points up toward the baseline. It does not start from the baseline and point down. That would indicate retrograde flow.
What system control should be adjusted to optimize this waveform?
A. Wall filter
B. Packet size
C. Gain
D. Pulse repetition frequency
E. Sample volume size
D. Pulse repetition frequency. Because aliasing occurs when the frequency shift exceeds ½ the PRF, the frequency at which aliasing occurs increases as the PRF increases. Depending on the ultrasound system, the PRF control may be called Velocity Scale, Velocity Range, Flow Rate, or other terms. Whatever it is called, it controls PRF.
You are performing a carotid duplex exam examination with the following parameters 5MHz doppler freq, 6 kHz PRF, 4cm depth and 1.5mm sample volume length. What is the aliasing freq?
3 kHz
Nyquist limit = 1/2 PRF
The rapid technique used in the most color doppler systmems to obtain the mean doppler freq shift
autocorrelation
Your patient has edema involving the right lower extermity. This may be caused by
Increased intravenous pressure
*higher transmural pressure - fluid leaking interstitial space causeing edema
Which of the following statements most correctly describes the occurence of diastolic flow reversal in the arterial system?
A) it is always an abnormal finding
B) it is seen in and proximal to high-resistance vessels
C) it is most commonly observed in vessels that supply low-resistance beds
D) it can be enhanced by body heating
E) it is found in the internal carotid artery
B
