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90 Cards in this Set

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  • Back
While evaluating the liver vasculature with color doppler, you are unable to obtain signals from the deeper vessels, what should you do to enhance your ability to demonstrate flow in the deeper vessels?
Decrease doppler frequency
What is the maximum velocity limit for a 3MHz CW Doppler unit operating at a depth of 4cm: 40cm/s,200cm/s, 2.5m/s, 4m/s, none
CW has range ambiguity so none
Aliasing of the doppler spectrum occurs whenever the frequency shift exceeds what?
1/2 the PRF
During a hepatic sonogram using color doppler imaging, there is no color signal detected within the portal vein, what could you do to improve sensitivity to slow flow?
Decrease the wall filter, Increase packet size, Increase color gain, Decrease the frequency
The ensamble lenght in color doppler refers to the number of what?
Pulses per scan line
While performing a doppler study of the SMA, your measurement of the Doppler angle if incidence was underestimated, what error will result from this mistake?
The velocity estimatio will be inacurate
A commonly used process for determining the direction in a doppler instrument is what?
Phase Quadrate Detection
What method is used to steer the color beam with a linear array transducer?
Elecrronic time delays
When color doppler is active, how many pulses per scan line are used to create the underlying B-mode image
What doppler technique does not provide range resolution?
CW doppler
You have obtained a color doppler image of the common carotid artery after employing a red/blue map. WITHOUT using invert, if the frequency is greater than the transmitted frequency, which of the following would be correct: Color encoding red/negative doppler shift, color encoding blue/negative doppler shift, Color encoding red/positive doppler shift, color encoding blue/positive doppler shift, or No doppler shift?
Color encoding red/positive doppler shift
Ailiasing is a potential problem in PW doppler, why?
Because of intermittent sampling
What does the power spectrum depict?
Relative importance of each frequency in the doppler signal
What is the result of increasing the wall filter during doppler sampling?
Reduce display of low frequency shifts
You have increased the packet size while using color doppler to evaluate flow in the thyroid gland, what negative result will occur from this action?
Decreased frame rate
You have increased the packet size while using color doppler to evaluate flow in the thyroid gland, what negative result will occur from this action?
Decreased frame rate
What positive result will occur from the action taken when You increased the packet size while using color doppler to evaluate flow in the thyroid gland
Improved signal to noise ratio
What method is most commonly used to perform spectral analysis for pulsed doppler?
FFT Fast Fourier Transform
What is the doppler frequency shift defined as?
The difference between the transmitted and recieved frequencies
According to the doppler equation which of the following is not true: Increasing doppler frequency will increase the frequency shift, Increasing doppler interrogation angle will increase the frequency shift, Decreasing the reflector speed will decrease the frequency shift, No frequency shift is detected when the doppler beam strikes the reflector with perpendicular incidence, or Velocity information can be obtained from the frequency shift if the angle of incidence is known?
Increasing doppler interrogation angle will increase the frequency shift is false.
The Nyquist limit describes what?
The aliasing frequency
What information does the z axis (brightness) on the doppler spectrum provide?
A waveform in the ICA obtained at a doppler angle of 45degrees shows aliasing, which of the following choices will NOT help you to unwrap this waveform: Increase the angle of incidence, Decrease the high pass filter, Lower the zero baseline, Increase the PRF, or Decrease the doppler frequency
Decrease the high pass filter
While performing a color doppler exam in the abdomen you have adjusted several system controls and notice that the frame rate has decreased, which of the following adjustments can you make to improve the color frame rate: Increase the packet size, Decrease the PRF, Decrease the color box, Increase scan line density, or Increase the wall filter
Decrease the color box
You are performing a carotid duplex examination with the following: 5MHz doppler freq, 6KHz, 4cm depth, and a 1.5mm sample volume length, what is the aliasing frequency?
The orapid technique used in most color doppler systems to obtain the mean soppler frequency shift is known as what?
What aspect of the doppler spectrum is color encoded with power doppler?
You have encountered spectral broadening of the ICA waveform, this most likely indicates what?
Turbulent flow
What term describes the number of pulses that are used to determine the velocity along a color line of sight?
Packet size
Which of the following methods will help you to demonstrate flow turbulence with color doppler: Autocorrelation, Variance, FFT, Zero crossing detection, or Phase quadrate detection?
What parameter describes the axial lenght of the sample volume for a color pixel?
Color gate
What type of Doppler device uses two transducers, one to reeive and one to transmit?
CW doppler
What is spectral analysis used to do?
Determine the distribution and magnitude of frequency shifts in the reflected doppler signal
Color flash artifact is obscuring the anatomy of interest in an exam of the Abd AO. What can you do to reduce the impact of the flash: Increase the color gain, Decrease the PRF, Increase the wall filter, Increase packet size, or Increase the doppler frequency?
Increase the wall filter
CW ultrasound can: sample specific areas, Sample a range of large areas, Can measure high velocities of blood flow, or has limitation of nyquist limit?
It can measure high velocities of blood flow
When the velocity of blood flow exceeds the doppler nyquist limit, what occurs?
An advantage of CW doppler over PW doppler is: Range resolution, Peak nyquist limit, Peak velocity detection, or Aliasing can be detected?
Peak velocity detection
When ultrasound waves travel through a medium which contains many small scatterers, the amount of sound that is scattered would do what?
Increase sharply with increasing frequency
The doppler shift frequency from moving reflectors is what?
The difference between the transmitted and received ultrasonic frequencies
Will Aliasing occur in: PW doppler, CW doppler, or Color doppler?
PW and Color doppler, not CW doppler
What factors are velocity calculations dependant on?
Speed of sound in tissue, Doppler angle, and Transmitted frequency
Color flow imaging utilizes what type of Doppler?
PW doppler
WAt what angle is the maximum doppler frequency shift detected?
60 degrees
The difference between the transmit frequency and the received frequency is called what?
Doppler shift
True or False: Aliasing is a diagnostic parameter for severe disease?
Power doppler is also referred to as what?
Amplitude imaging
Color flow doppler provides what type of velocity information?
The Nyquist limit is equal to what?
1/2 the PRF
True or False: In laminar flow the blood is faster near the vessel walls?
No flow in a vessel would be indicated by what color?
What is the simplified bernouli equation?
CW doppler utilizes how many elements?
Color frame rate is affected by all of the following except what: Sector size, Color box size, Color gain, or PRF
Colro gain
What are the two catagories of energy that make up total fluid energy?
Potential and kinetic energy
What type of processing is utilized with most color flow systems?
True or False: Power doppler can detect flow direction?
Power mode differes from color dopppler by evaluating what?
The amplitude of the signal
Window filling of the spectral tracing is due to what?
Turbulent flow, Sample gate too large, SV placed too close to the vessel wall, Gain to high
What angle provides the maximum doppler shift angle?
All of the following are true regarding power doppler except which: Greater sensitivity than color doppler, Doppler angle has little effect on flow detection, slower image rates, or less flash artifact?
Less flash artifacts
What do you expect to see with a high reynolds number?
Turbulent flow
True or False: Blood flow is most turbulent proximal to a stenosis?
True or False: A minimum of 3 pulses per scan line is required to assign color?
True or False: Vascular resistance is determined by the radius of the blood vessel?
There is no turbulence of blood whan the Reynolds number is less than what?
True or False: Potential energy may be increased when blood changes speed and direction?
What color assignment to flow towards the transduce?
What are the units of measure for doppler shift?
True or False: Color aliasing is seen when the red and blue are seperated by black?
What is the minimum number of pulses required for color to be displayed using autocorrelation technique?
True or False: Color dopppler has less velocity information than spectral doppler?
All of the following are true regarding color doppler except: Color doppler will not alias, color doppler is qualitative data, color doppler is a pulse doppler technique, or color doppler uses autocorrelation processing?
Color doppler will not alias is flase
True or False: The return signal in color doppler is an average of the signals from many blood cells?
Which technique allows the display of amplitude signals from the blood cells?
Power doppler
True or False: Amplitude imaging takes a long time to process compared to color doppler?
All are true regarding amplitude imaging except: It is a quantitative technique, it has good sensitivity to slow flow, it is not angle dependent, or it can not display direction of flow?
It is a quantitavie technique is false
The amplitude of returning signals is dependent upon which factors?
Density of RBCs, blood/tissue signal separation, size of vessels in relation to sample volume size, attenuation
Low velocity high amplitude signals can be eliminated from spectral tracing how?
By use of the wall filter
Lowering the doppler transmit frequency will provide increased penetration and will provide what type of reflected frequency shifts?
Reflections from the blood are known as what?
Rayleigh scattering
True or False: Color doppler does not display mean frequency, direction of flow and turbulence
True or False: Spectral doppler displays flow direction turbulence and peak velocity information?
True or False: Power doppler displays existence of flow but no direction information?
Is Vascular resistance: Directly, Inversely, Logithimically, or not proportional to the radius of the vessel?
The flow of blood through the body is affected by which of the following factors: Density, Size of the vessel, pressure gradient, or all of them
All of them
What is the difference between FFT and autocorrelation doppler techniques?
Autocorrelation can olnly provide mean values of doppler shift
In order to increase the Nyquist limit and correct aliasing you would: Increase PRF, not change PRF, or Decrease PRF?
Increase PRF
The color image and spectrum analysis provided are indicative of a high grade stenosis because of what?
Elevated peak velocity and post stenotic turbulence
By increasing the doppler angle between the incident beam and the direction of blood flow, the result would be an increase in what?
Increased potential for error in calculating velocity
Which statement is not true regarding color doppler imaging: color doppler requires a min of 3 pulses per scan line, color doppler can alias and has limitations, color doppler is a quantitative technique, or color doppler utilizes PW doppler?
Color doppler is a quantitative technique