Physics Quiz 4
To increase accuracy, up to ___ pulses are used with the ________________ technique
10 autocorrelation
a minimum of _____ pulses are used to obtain velocities from each point with *cross-correlation*
2
A minimum of ________ pulses are needed to obtain velocity information for each gate location with the _____________ technique
3 autocorrelation
When color Doppler is active, how many pulses per scan line are typically used to create the underlying B-mode image? A: 1-2 B: 3-4 C: 5-6 D: 7-8 E: 9-10
A: 1-2
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
What aspect of the Doppler spectrum is color-encoded with color Doppler? A: Amplitude B: Frequency shift C: Power D: Velocity E: Bandwidth
D: Velocity
Volume flow is determined by multiplying the cross sectional area of the vessel with: A: Volume flow rate B: Mean velocity C: Peak velocity D: Minimum velocity E: Velocity range
B: Mean velocity
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: Phase quadrature detection
B: Variance
What does BART stand for?
Blue-Away, Red-Towards
What information is colorized in an image using power Doppler? A) Frequency shift B) Flow veocity C) Doppler signal amplitude D) Frequency bandwidth E) Acoustic power
C) Doppler signal amplitude
What information is colorized in an image using power Doppler? A) frequency shift B) flow velocity C) Doppler signal amplitude D) frequency bandwidth E) acoustic power
C) Doppler signal amplitude
When performing a color Doppler exam in the abdomen you have adjusted several system controls and notice that the FR has decreased. Which of the following adjustments can you make to improve the color FR? A) increase packet size B) decrease PRF C) decrease the color box width D) increase the scan line density E) increase wall filter
C) decrease the color box width
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 artifact C) increased color writing on vessel wall D) increased FR E) improved color penetration
C) increased color writing on vessel wall
Doppler color flow imaging: A) is based on the Doppler affect B) is not affected by the direction of blood flow C) is affected by direction of blood flow D) is not affected by aliasing E) eliminates angle correction in velocity calculations
C) is affected by direction of blood flow
The term "variance" refers to: A) peak velocity B) mean velocity C) velocity range D) velocity threshold E) frequency threshhold
C) velocity range
3 kinds of power Doppler:
Ultrasound angiography Amplitude Doppler Color Amplitude Imaging (CAI)
definition of color flow imaging:
Ultrasound technique producing grey-scale images with superimposed colors indicating blood-flow velocity and direction
___________________ flow velocity projects on the line of insonation as an arrow towards the probe.
Vector of Blood
In color map *variance* mode, all of the velocities for a particular location are _____________. ___________________ is displayed in color. Variability between the velocities is then ____________. If variability is _______ (__________ flow), a different color (usually green or yellow) is assigned to the pixel.
averaged mean velocity estimated high turbulent
information on flow direction is preserved with:
bidirectional power Doppler
on a color map, what color represents flow at 90 degrees to the sound beam?
black
The power Doppler image indicates only that __________ __________ is present; they contain no information on flow __________
blood flow velocity
The deeper the _________ ____________ of the box, the longer it takes to obtain each line
bottom border
2 methods of velocity detection:
color Doppler cross-correlation
Area evaluated with color is:
large (color box)
In color doppler, large amount of information about velocities is received due to:
large gate and multiple lines
Vector of Blood flow velocity projects on the_______________________ as an arrow towards the probe.
line of insonation
Power Doppler is very sensitive to ______ flow velocities even with poor _______
low angle
Flow Speed: colors closer to the black line indicate ___________ ______________, and colors further away from the black line indicate _____________ ______________.
lower velocities higher velocities
Autocorrelation: Deviations from the ________ velocity can be also obtained and represented in different color
mean
the accuracy for color Doppler is via:
mean or modal velocities
Cross-Correlation: Deviations from the _______ velocity can be also obtained and represented in different color (variant mode)
modal
With cross-correlation, the most commonly occurring velocity (_________ velocity) is displayed in ______ (____________ _____________)
modal color (velocity mode)
Mean vs Modal:
modal is the most commonly occurring mean is the average
In order to accurately determine the velocity of the RBC, the system:
obtains Doppler shift from several pulses and averages it
The more pulses in the packet, the more ________ is needed. How does this affect TR?
time decreases FR, bad TR
Flow __________ the transducer is always above the black horizontal line, and flow ________ from the transducer is always below the horizontal black line
towards away
A single color Doppler display line is produced by:
transmitting multiple lines (packet) in the same direction and then correlating the data within the packet
Variance color map has variations in color:
up and down and side to side
3 color map types:
velocity variance power
The gate is then determined by the _________ _____________ of the box
vertical size
The __________ the box, the more lines it contains
wider
3D info (x) x (y) x (pixel color) for spectral:
t x v x A
When the isonification angle is greater than ____ degrees, the cosine is negative
90
when the angle of flow is less than _____ degrees, the flow direction is considered towards the probe
90
What parameter describes the axial length of the sampling volume for a color pixel? A) color gate B) packet size C) PRP D) PRF E) Line density
A) color gate
what parameter describes the axial length of the sampling volume for a color pixel? A) color gate B) packet size C) PRF D) PRP E) line density
A) color gate
What positive result will occur from increasing the packet size while using color doppler? A) improved SNR B) reduced aliasing C) improved LARD D) improved LATA E) improved TR
A) improved SNR
The amplitude of scattered echoes from RBCs is LEAST affected by: A) reflector velocity B) attenuation of ST C) transducer f D) hematocrit
A) reflector velocity
Which of the following statements about formation of the color Doppler image is true? A) The color and B-mode images are generally derived from the same pulse. B) The color image is superimposed on top of the existing B-mode image. C) The color and B-mode images are generally formed using the same frequency sound. D) The B-mode image is usually obtained at a lower frequency than the color image. E) The color image generally has a higher spatial resolution compared to the B-mode image.
B) The color image is superimposed on top of the existing B-mode image.
When the velocity scale of the color map is 17 cm/s, and the flow is at 0 degrees to the sound beam axis, the colors on either end of the bar would represent: A) peak velocity of 17 cm/sec B) average velocity of 17 cm/sec C) peak velocity of 34 cm/sec
B) average velocity of 17 cm/sec
Increasing the color packet size results in: A) better velocity estimates, higher FR B) better velocity estimates, lower FR C) worse velocity estimates, higher FR D) worse velocity estimates, lower FR E) better velocity estimates, unchanged FR
B) better velocity estimates, lower FR
What term describes the number of pulses that are used to determine the velocity along a color line of sight? A) color gate B) packet size C) PRF D) PD E) PRP
B) packet size
The rapid technique used in most color Doppler systems to obtain the mean Doppler frequency shift is: A: Fast Fourier transform B: Phase quadrature C: Autocorrelation D: Zero-crossing detector E: Variance
C: Autocorrelation
What two controls affect the spatial resolution of the color image? A: Line density and ensemble length B: Ensemble length and priority C: Frequency and line density D: Frequency and ensemble length E: Priority and frequency
C: Frequency and line density
Color flash artifact is obscuring the anatomy of interest in an exam of the abdominal aorta. What can you do to reduce impact of the flash? A: Increase the color gain B: Decrease the pulse repetition frequency C: Increase the wall filter D: Increase the packet size E: Increase the Doppler transmit frequency
C: Increase the wall filter
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 FR
_________ mode obtains velocity measurements from ___________________________ within a color box
Color multiple lines
A Doppler device without a spectrum analyzer CANNOT display: A) peak velocity B) mean velocity C) velocity changes over time D) distribution of reflector velocities
D) distribution of reflector velocities
The pixel color on a color flow velocity image represents: A) amplitude of echoes from blood B) blood velocity independent from the angle C) flow direction D) movement of blood and tissue E) movement of blood but not tissue
D) movement of blood and tissue
The packet size in color Doppler refers to the number of: A) pulses per second B) sample volumes per scan line C) scan lines per unit area D) pulses per acoustic scan line E) pulses required to create one frame
D) pulses per acoustic scan line
technique used for spectral:
Doppler
how is the blood flow velocity calculated in color doppler?
Doppler equation
technique used for color doppler:
Doppler or cross correlation
3 other names for packet size:
Doppler packet ensemble length dwell time
*Autocorrelation*: Comparing 2nd and the 3rd pulse yields the:
Doppler shift
Similar to spectral analysis, color Doppler shift is calculated: (formula):
Doppler shift = fe-fo
Which of the following could be used to increase the color FR for a cardiac image? A) decrease the image width B) decrease packet size C) decrease line density D) A and B E) All of the above
E) all of the above
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 doppler sample volume E) all of the above
E) all of the above
Color flow imaging is presented in three dimensions:
Length Width Velocity (color)
Is FFT used in color Doppler? Why or why not?
No FFT analyzer is not fast enough to process
definition of packet size:
Number of pulses used for averaging
What does RABT stand for?
Red-Away, Blue-Towards
In color map *velocity* mode, all of the velocities for a particular location are ____________. ____________________ are displayed in color
averaged mean velocites
the accuracy for spectral is via:
Spectrum of velocities; can evaluate PSV, EDV, etc.
3D info (x) x (y) x (pixel color) for color doppler:
W x L x v
The area evaluated with spectral is:
Within a gate along one line
Power Doppler plots _________ vs __________ on the graph
amplitude Doppler shift
How is velocity information obtained within the color box?
an individual pulse (or group of pulses) is sent for each line
What is the insonification angle?
angle to flow
What technique is used instead of FFT in color doppler?
autocorrelation
All the velocities for a particular location are ___________ in *autocorrelation*. The ___________ (___________) velocity is displayed in ____________ (___________ __________)
averaged mean (average) color (velocity mode)
To obtain one frame, the ________________ is first scanned ________ _____ ________ to create gray scale image, then area within color box is _____________ to obtain velocity information: an individual pulse (or group of pulses) is sent for each line
entire area line by line rescanned
Color yields an ____________ of the _________ velocity, not the distribution of the velocities as does spectral doppler
estimate mean
Transducer orientation in long axis (sagittal): Probe notch towards the ________ "m" on the _____ of the screen (patent's _______)
head left head
The ________________________ is estimated and color coded.
integral of power spectrum
*Autocorrelation*: Comparing 1st and the 2nd pulse yields the:
phase difference (flow direction)
The more ____________________________, the more accurate the velocity measurement
pulses within the packet
is spectral Doppler considered quantitative or qualitative? is color flow Doppler considers qualitative or quantitative?
quantitative qualitative
what does the cross-correlation method use to calculate blood flow velocity?
range equation
Flow is _________ directly away or towards the probe
rarely
Transducer orientation in cross-section (transverse): probe notch to patient's ________ "m" on the ______ of the screen (patent's ______)
right left right
larger packet sizes produce _________ color with less _________, but further degrades ________
smooth noise TR