Final

What happens to the Doppler shift frequency if the initial transmit frequency changes from 4.0 MHz to 2.0 MHz?

reduced by 1/2

What is the term for strong signals created often by stationary reflectors when they are interrogate within the Doppler beam?

clutter

Looking at this color bar, how would a color Doppler system show blood flow that is accelerating?

the color shifts from a darker hue to a brighter hue

If the angle of insonation decreases from 60° to 30°, the Doppler shift will

increase

Which of the following color controls selects the gray-scale echo strength below which the color will be shown at each pixel location?

Color Write Priority

1. Alaising and flow rversal

2. Improper color box angle placement

3. We want to flip the color to the left side of the screen to go with the vessel

How would you describe the type of spectral Doppler flow observed in this image?

turbulent

duplication of Doppler Information on opposite sides of a strong reflector

Mirror Image

occurs when the Doppler shift exceeds the NL

Aliasing

Most common artifact associated with power Doppler

Flash

Doppler electronic signal seen due to gain settings being set too high

Spectral Nolse

Color extending outside vessel walls

Color Bleeding

The artifact most often seen with the ultrasound beam is perpendicular to blood flow

Multiple Angle/Color Drop Out

Echoes return after the next pulse is emitted

Range Ambiguity

What is the signal in power Doppler proportional to?

RBC concentration

T/F: The most common artifact encountered in color Doppler ultrasound is range ambiguity.

False

Which of the following would result in an increase in Doppler shift frequency?

Increasing blood flow velocity

What process causes the aliasing artifact on a spectral Doppler waveform?

sampling Doppler shift frequencies at a low rate

When collecting data for spectral Doppler evaluation, what determines the amplitude of the Doppler sft frequencies?

number of red blood cells

T/F

False

Low-velocity venous flow is not visualized on spectral Doppler

Which adjustment is MOST appropriate?

Decrease wall filter

What may happen to a color flow image if the color gain is set too low?

false indication of limited or no flow

Which term correctly describes the multiple pulses of sound used to create a color flow image?

color packet

the maximum average speed of velocities without aliasing

If the flow speed is doubled, what happens to the Doppler shift?

doubled

Which statement best describes the desired optimal Doppler frequency for ultrasound clinical applications?

lowest possible frequency

cephalic to caudal

1. I would increase the PRF to get rid of aliasing

2. I would decrese the size of the smaple gate to avoid picking up slow flow close to the walls (fill in in the spectral window/spectral broadening)

3. I would Increase my wall filter to get rid of those low signals shown in the waveform

What mathematical technique does Color Doppler utilize?

autocorrelation

Artificial spectral broadening on the spectral display can be produced by which of the follow settings?

excessive sample volume length

If operating frequency is halved, what happens to the Doppler shift?

halved

If the highest Doppler-shift frequency present in p signal exceeds_______ the PRF, aliasing will occur?

one half

A technologist sets Doppler angle correction at 80° while sampling the femoral artery.

What is the MOST significant effect?

Velocity will be underestimated

T/F: The Doppler shift frequency is directly proportional to the velocity of the red blood cells.

True

Range ambiguity artifact produces which error in the spectral Doppler study?

ambiguous gate locations

According to the lecture/lab, what is the first step a sonographer should do to remove aliasing from a spectral Doppler waveform?

increase the PRF

decrease color gain

When the spectral window of a Doppler waveform is filled in, what does this usually indicate?

turbulent flow due to pathology

What spectral Doppler artifacts are noted in this cardiac evaluation? How would you optimize the image?

Aliasing and clutter. We can increase PRF to get rid of aliaisng, and we can increase the wall filter to ger rid of the clutter.

In this image above, what parameter was changed between A and B? How would you further optimize this image?

On image B the PRF was increase and the AC was decrease from 49 to 46 degrees, to get rid of the alaising shown on image A. I would increase the wall filter to get rid of the clutter at the baseline and get rid of the fill in of the spectral window (turbulent flow) I could also try decreaseing the Spectral gain to get rid of the noise above and below the waveform.

Alliasing, alaising can happen when high doppler shift velocities that are exceeding the nyquist limit causing wraping around at the baseline. We can do different things to fix it but in this case I would increasing the Scale/PRF to increase the nyquist limit and sample faster those faster velocities in the middle.

away from the transducer

Steering the color FOV to the right or left produces a(n)_______ frame rate.

unchanged

What is another name for the wall filter in a Doppler system?

high pass filter

T/F: The Doppler angle is less critical at larger angles than at smaller ones.

False

Within spectral Doppler, why is FFT is used to display a range of frequency shifts?

The RBCs are moving at different velocities and at different Doppler angles.

What is displayed in a spectral Doppler waveform of blood flow?

flow velocity verses time

At an angle of 90 degrees there is no detectable Doppler shift due to

the cosine of 90 degrees is zero

What is the function of the Cosine in the Doppler shift equation?

it relates relative motion towards or away from the sound source

A technically optimized carotid Doppler exam shows marked spectral broadening distal to a plaque.

What MOST likely explains this finding?

Turbulent flow from stenosis

If the sound source and the observer are moving in the same direction at the same velocity, what type of Doppler shift is demonstrated?

no Doppler shift

What is the optimal Doppler frequency for general clinical applications?

Lowest frequency possible

Which control on a PW Doppler system allows the sonographer to input the Doppler angle into the system?

Angle correction

What is the effect on the spectral waveform for a PW Doppler system that is experiencing range ambiguity?

Clutter

What may happen to a color flow image if the color gain is set too low?

False indication of limited or no flow

What is the benefit of steering the color field of view (color box) during color flow imaging?

To create better Doppler angle

Adjusting the velocity scale on a color Doppler imaging system changes what Doppler parameter within the system?

PRF

What do lighter shades of color usually depict in a normal blood vessel or normal chamber of the heart?

Faster flow velocities

What will happen if the scanning system’s settings are not carefully documented and reused during a series of QA tests?

A false indication of degradation in the system’s performance

According to Dr. Miele, which component of a modern scanning system is most likely to fail?

Transducer

T/F: What component creates the Doppler shift during cardiovascular applications?

False

How many times per cycle must a Doppler system sample the Doppler frequencies to prevent the aliasing artifact?

Two

What is the mathematical process used to break the Doppler shift frequency into individual frequencies?

FFT

How is a spectral Doppler system able to specify a specific depth for gathering blood flow information?

Electronic range gating

What is the function of the wall filter in Doppler system?

Remove clutter from the Doppler signals

Which technique CANNOT eliminate aliasing?

Increasing transducer frequency

What is the major advantage of CW Doppler when compared to PW Doppler systems?

The color shifts from a darker hue to a brighter hue

When is range ambiguity most likely to occur with a PW Doppler system?

At shallow sample volume depths

In a positive Doppler shift, the transmitted frequency should be?

Lower than the received frequency

If the Doppler shift frequency increases the relative velocity does what?

Increases

What are the three situations where the echogenicity of blood increases?

Stationary blood, turbulent flow, thrombus

How does a specular reflection at the wall of a vessel reduce the intensity of the sound beam used to interrogate it

By reflecting most of the energy back to the transducer

What does turbulent blood flow usually indicate?

Cardiovascular disease

What is considered a normal hematocrit value for a healthy female?

42%

What effect will polycythemia Vera have on a patient’s hematocrit?

Increase

The ability to do work

Energy

A measure of force per unit area

Pressure

A measure of the ability to hold a change in volume

Capacitance

How does an increase in resistance to flow in the aortic valve affect the heart in the long run?

Left ventricular foundation can be negatively affected

Which term describes the increase in pressure in a flowing fluid distal to a narrowing of a tube?

Pressure recovery

Flow in the arterial system of the human body?

Arterial flow

Flow whose profile demonstrates slow flow at the walls and increasing flow velocity near the center of the vessel

Parabolic flow

When examining Poiseuille’s law, what effect will doubling a vessel radius have on the volume flow rate (Q) ?

Increases 16 times

Where is the highest resistance to blood flow found in the normal cardiovascular system?

Arterioles

Approximately what percentage of the cardiovascular system’s blood is stored in the venous system of a person at rest?

65%

What is “pulsatile” blood flow?

Flow that rapidly accelerates and gradually decelerates

How does the body maintain volumetric flow to distal organs in the presence of an arterial stenosis?

Increased flow velocity through the stenosis

Which statement about hemodynamics is correct for vessels connected in series?

Overall flow resistance increases

What happens in the vascular system when an arterial stenosis lowers the amount of blood going to the end organs?

Ductal arterioles dilate and lower resistance to flow

When examining Poiseulle’s law what effect does reducing the length of a vessel by ½ have on the volumetric flow?

It doubles