Description
Sonogram, Vascular
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Explanation & Answer
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Ridgeway CH 14 – A Doppler Miscellany
1.) What causes the frequency shift to occur when using spectral Doppler to image
blood flow?
The change in frequency between the sound source and the receiver by either being too
close to each other far from each other. The shift in frequency aid in the evaluation of the
flow velocity and assess how severe a disease is.
2.) What is the difference between frequency shift and velocity of blood flow?
The frequency shift is based on reflected frequency, and the transmitted frequency is
displayed in Hz while the blood flow velocity is the speed and rare that the blood cells
are traveling shown in m/s.
3.) Draw an example of a Spectral Doppler waveform and describe each component.
4.) How does the velocity of blood flow change the frequency shift?
If the blood flow is moving faster, the frequency shift will be higher. If the blood flow is
moving slower, the frequency shift will be lower
5.) How does the operating frequency of the transducer change the frequency shift?
When the operating frequency of the transducers doubles the frequency shift double
showing a direct relationship.
6.) How does the angle of the Doppler beam relative to the direction of blood flow
change the frequency shift? What is this angle called?
Depending on the relationship between the directions the red blood cell is traveling and
the direction of the sound wave when they meet the angle can change. By moving
directly towards or away from each other is most accurate angle obtained can be cousine
angle.
7.) Explain the difference between angle of incidence (angle theta) and cosine angle?
The angle of incident and cosine has an indirect relationship. As the angle of incidence
moves closer to 90, the cosine moves closer to 0, and as angle of incidence moves closer
to 0, the cosine moves closer to 1
8.) List and define the Doppler equation that is used to convert frequency information
into velocity information on the ultrasound machine.
DF = 2(Ft) (cosΘ) V / C
V = (DF)(C) / 2(Ft)(cosΘ)
Ridgeway CH 14 – A Doppler Miscellany
Where
C = the speed of sound in tissue (1.54 m/ sec)
ΔF = Doppler frequency shift
Ft = transducer frequency.
9.) What part does the correct angle knob on your machine play in this equation?
It allows the sonographer to line up most accurately (angle bar parallel to vessel walls).
Changes the angle theta, which changes the cosine, which changes the velocity
measurement result
10.)
Explain the difference between steering the color flow and spectral Doppler
beam angle to the walls of the vessel versus the angle of the stenotic lesion
By being close to the cell wall the spectral Doppler angle results to high frequency
Doppler signals which can depict the stenotic lesion. Steering the color on the hand
enable the lesion to well depict through bright brighter colors.
RIDGEWAY CHAPTER 12 LECTURE OBJECTIVES
1. Describe the 3 basic uses for color flow in vascular studies?
Color flow is essential as it is used in showing the velocities of blood flow, coding for
directions and showing real time flow information superimposed on real time
morphological data.
2. What do the colors correspond to when using Color flow?
The red color is used in indicating blood flow towards the transducer. The blue can
depicts blood is flowing away from the transducer. The velocity of the flow is shown by
different color brightness.
3. Explain how color flow analysis differs from spectral Doppler analysis?
The color flow analysis uses color to show Doppler shift while the spectral Doppler
analysis uses waveform to show Doppler shift.
4. Why is the machine’s frame rate affected? What settings could be changed to
increase the frame rate?
The machine frame rate is affected by increas...