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Ultrasound Physics > SPI #5 Hemodynamics and Doppler Principles > Flashcards

SPI #5 Hemodynamics and Doppler Principles Flashcards

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1
Q

What provides the potential energy in the cardiovascular system?

  • Distal arterioles
  • Blood flowing through the vessels
  • Beating heart
  • Venous system
A

The heart provides the potential energy at the beginning of the cardiovascular system

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2
Q

What is another term for gravitational potential energy?

  • Kinetic energy
  • Viscous energy
  • Inertial energy
  • Hydrostatic pressure
A

Hydrostatic pressure is pressure from gravity

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3
Q

What is the name of the flat flow profile that is seen at the entrance of vessels?

  • Plug flow
  • Laminar flow
  • Turbulent flow
  • Chaotic flow
A

Plug flow is the flat flow profile at the entrance of vessels.

Plug flow occurs in large vessels (like that aorta) and at the entrance of vessels

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4
Q

What does increasing the PRF/scale setting on a spectral Doppler do?

  • Increases the potential of aliasing
  • Decreases the potential of aliasing
  • Makes the spectral waveform appear larger
  • Optimizes the system to detect slow flow
A

When you increase the PRF/scale setting the Nyquist limit is increased which decreases the potential of aliasing.

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5
Q

Which of the following is seen with continuous wave instrumentation?

  • Transducer frequency matches that of the oscillator
  • Sample depth can be determined by a range gate
  • Very short pulses are used
  • Aliasing limits velocity measurements
A

CW transducer frequency matches that of the oscillator.

Frequency of continuous wave transudcers is determined by the oscillator frequency

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6
Q

When is the Doppler shift highest?

(a) Doppler shift is unrelated to beam angle
(b) When the beam is perpendicular to the direction of flow
(c) When the beam is parallel to the direction of flow
(d) When the beam is at a 45 degree angle to flow.

A

Doppler shift is highest when the beam is parallel to flow (at 0° angle)

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7
Q

Which of the following will not eliminate aliasing?

  • Increasing the PRF
  • Increasing the Nyquist limit above the frequency shift
  • Decreasing the sample depth
  • Increasing the frequency shift above the Nyquist limit
A

Increasing the frequency shift above the Nyquist limit will NOT eliminate aliasing.

In order to eliminate aliasing, the frequency shift needs to be decreased.

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8
Q

When a reflector moves toward the transducer, what will happen to the reflected frequency?

  • Increase
  • Decrease
  • Stay the same
  • It is not possible to predict
A

As the reflector moves toward the transducer the reflected frequency will increase

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9
Q

Which of the following has to be increased in order to see an increase in flow volume?

  • Pressure difference
  • Resistance
  • Vessel length
  • Viscosity
A

Increasing the pressure difference will increase the flow volume

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10
Q

Adjusting which of the following will have no effect on the measured frequency shift?

  • Flow velocity
  • Operating frequency
  • Amplitude
  • Propagation speed
A

Adjusting amplitude will not effect the measured frequency shift

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11
Q

Which of the following is representative of Ohm’s law?

  • V = IR
  • I = R/V
  • R = I/V
  • R = VI
A

Ohm’s Law:

V = IR

Voltage = Current x Resistance

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12
Q

What is the point at which Reynolds number predicts turbulence?

  • 500
  • 1200
  • 2000
  • 4000
A

2000

A Reynolds number >2000 indicates turbulence.

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13
Q

In order to maintain flow as a constant, if the area of a vessel increases what must happen to the velocity?

  • It increases
  • It decreases
  • It does not change with changes in area
  • Not enough information
A

As the area of a vessel increases, velocity will decrease

Q = VA
To maintain the flow, area increases and velocity will decrease

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14
Q

Which of the following is NOT a way in which venous blood is assisted in returning to the heart?

  • Calf muscle pump
  • Inspiration
  • Expiration
  • Venous valves
A

Inspiration

does not assist in venous blood returning to the heart

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15
Q

In a standing patient, where is the hydrostatic pressure the highest?

  • In the feet
  • In the arms
  • In the abdomen
  • Near the heart
A

Hydrostatic pressure is highest at the feet

Gravity causes the highest pressure to be in the feet of a person standing upright.

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16
Q

A stenosis of 75% in area is equal to what percent of stenosis in diameter?

  • 25%
  • 50%
  • 75%
  • 100%
A

75% decrease in area = 50% decrease in diameter

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17
Q

In the exercising patient, what is the response to peripheral resistance with arteriolar dilatation?

  • The peripheral resistance increases
  • The peripheral resistance decreases
  • There is no change in peripheral resistance
  • Peripheral resistance would decrease but only in presence of disease
A

In an exercising patient, the peripheral resistance decreases.

Exercise in a normal patient causes vasodilatation, which causes decreased peripheral resistance.

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18
Q

Which of the following will be seen with a stationary reflector?

  • There is a higher reflected frequency compared with the incident frequency
  • There is a lower reflected frequency compared with the incident frequency
  • The incident frequency is equal to the reflected frequency
  • The refelected intensity is higher than the incident intensity
A

For a stationary reflector, the incident frequency is equal to the reflected frequency.

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19
Q

What happens as the frequency of the transducer increases?

  • Penetration ability is increased
  • The amount of scatter is increased
  • The frequency shift is decreased
  • The amount of attentuation is decreased
A

As transducer frequency is increased, the amount of scatter is increased

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20
Q

What occurs as the Doppler angle is increased?

  • It decreases the frequency shift
  • It increase the frequency shift
  • It decreases the risk for aliasing
  • It improves the accuracy of the velocity calculation
A

As Doppler angle increases, the frequency shift decreases

An increase in the Doppler angle causes a decrease in the frequency shift because the frequency shift is calculated based on the cosine of the angle, not the angle itself.

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21
Q

What is the component of the ultrasound machine used to detect positive versus negative frequency shifts?

  • Analog Doppler
  • Oscillator
  • Fourier transformer
  • Phase quadrature
A

Phase quadrature is the processing technique used to detect positive versus negative frequency shifts

22
Q

Which of the following is true for continuous-wave Doppler devices?

  • It only needs to have one piezoelectric element
  • It must have at least two pizeoelectric elements
  • It must have three piezoelectric elements
  • No piezoelectric elements are needed for CW Doppler
A

For continuous-wave Doppler devices, it must have at least two pizeoelectric elements

In CW transducers, one element continuously sends and the other continuously receives

23
Q

Which of the following will result in aliasing?

  • Too low an operating frequency
  • Increased sampling of the blood flow
  • Undersampling of the blood flow
  • Too high a Doppler angle
A

Undersampling of the blood flow will result in aliasing.

Aliasing results when the signal is not sampled often enough.

24
Q

Which mathematical processing technique is used to analyze the data and produce a spectral waveform?

  • Amplitude shifting
  • Autocorrelation
  • Amplitude sampling
  • Fast Fourier transform
A

Faster Fourier transform (FFT) is the signal processing technique used for spectral Doppler.

25
Q

Which of the following represents the resistive index?

(a) Peak systolic velocity (PSV) minus the end diastolic velocity (EDV) divided by the mean velocity
​(b) EDV minus the PSV divided by the PSV

(c) PSV minus the EDV divided by the PSV
(d) PSV minus the EDV divided by the EDV

A

RI = PSV - EDV/PSV

26
Q

What does the brightness of the dots that make up the spectral display represent?

  • The number of red blood cells present
  • The velocity of the signal
  • The frequency shift
  • THe amount of turbulence present
A

Brightness of the dots that make up the spectral display represents the number of red blood cells present.

27
Q

What is said to occur when the window of the spectral Doppler display is filled-in?

  • There is spectral broadening
  • There is laminar flow
  • The Doppler gate is small and centered within the vessel
  • There is only one velocity at a given point in time
A

Spectral broadening is a widening of the envolope of the spectral Doppler waveform and appears as a filling in of the spectral window

28
Q

In order to add more spectral Doppler waveforms to the display, what setting on the machine should be adjusted?

  • PRF
  • Sweep speed
  • Heart rate
  • Gain
A

The sweep speed adjusts the number of waveforms that appear on the spectral display at one time.

29
Q

Which of the following may result if the spectral Doppler gain is too high?

  • Too much output power sent into the patient
  • Undermeasurement of the velocities
  • Overmeasurement of the velocities
  • An image that is too dark
A

When the spectral gain is too high, the velocities may be overestimated.

30
Q

The Doppler shift is lowest at what angle to flow?

  • 0°
  • 45°
  • 60°
  • 90°
A

At a 90° angle to flow, the Doppler shift is lowest/zero

31
Q

Which signal processing technique used for color Doppler is not as accurate, but faster, than the technique used for spectral Doppler?

  • Zero crossing
  • Phase quadrature
  • Autocorrelation
  • Fast Fourier transform
A

Autocorrelation is the signal processing technique used for color Doppler imaging.

32
Q

What is the fewest number of crystals a PW Doppler device may have?

  • Zero
  • One
  • Two
  • Three
A

A PW Doppler device needs only one active element/crystal.

33
Q

Which type of Doppler does not rely on the frequency shift but instead relies on the strength of the shift?

  • Spectral Doppler
  • Power Doppler
  • Color Doppler imaging
  • CW Doppler
A

Power Doppler does not rely on the frequency shift, but on the strength of the shift.

34
Q

What is it called when the 2D image, color Doppler image, and spectral Doppler are displayed simultaneously?

  • Duplex mode
  • Triplex mode
  • Phase quadrature mode
  • Multiplex mode
    *
A

Triplex mode is when the spectral waveform is diplayed along with the color and 2D image

35
Q

What is the duty factor of CW Doppler?

  • 1
  • 100
  • 0.01
  • 1%
A

Duty factor of CW beam is 1 (100%)

CW - continuous! Alway on. 100% of the time

36
Q

Which of the following is true about CW Doppler?

  • The measured frequency shifts come from a user-selected depth
  • A range gate is placed in the vessel to be sampled
  • There is a large sample volume that obtains signals from all vessels within
  • Pulses of sound are sent into the tissue to measure the frequency shifts.
A

CW beams have a large sample volume that may sample several vessels at once.

37
Q

When compared to 2D grayscale imaging, which of the following color Doppler statements is true?

  • There is improved temporal resolution
  • There is worse temporal resolution
  • There are fewer pulses per scan line
  • There is a higher frame rate
A

Color Doppler has worse temporal resolution compared to 2D grayscale imaging.

38
Q

Which of the following statements is false?

  • Aliasing does not occur with color Doppler
  • Continuous wave Doppler is able to measure very high frequency shifts
  • Pulsed wave Doppler has range resolution
  • Power Doppler is not limited by 90° angle
A

FALSE - Aliasing does not occur with color Doppler

Color Doppler is a PW technique and therefore has the same limitation on PRF as spectral Doppler

39
Q

WHich of the following frequency shifts would exhibit aliasing if the PRF is 5000 Hz?

  • 1.0 kHz
  • 2.5 kHz
  • 3.0 kHz
  • None of the above
A

Aliasing would occur at 3.0 kHz

Because aliasing occurs at a frequency shift greater than 1/2 PRF.
PRF at 5000 Hz, then Nyquist limit is 2500 Hz.
Anything more than 2.5 kHz would exhibit aliasing.

40
Q

Which of the following is true about the frequency shift?

(a) It increases with an increase in Doppler angle
(b) It is typically greater than 20,000 Hz
(c) It is inversely related to operating frequency
(d) It is in the audible range of sound

A

Frequency shift is in the audible range of sound

The frequency shift is typically 1/1000th of the operating frquency which is in the audible range of sound (20 Hz to 20 kHz)

41
Q

What can be said about the ensemble length of pulsed wave Doppler?

  • It is less than 2 pulses per scan line
  • It is more than 100 pulses per scan line
  • It is about 10 to 20 pulses per scan line
  • It is typically 0
A

The typical ensemble length is 10 to 20 pulses per scan line, but may be as low as 3.

42
Q

What happens if blood flow is sampled in the center of laminar flow?

  • There will be a higher velocity than if sampled toward the edges
  • There will be slow velocity than if sampled toward the edges
  • It will be made up of many different velocities
  • It will be turbulent
A

There will be a higher velocity than if sampled toward the edges if sampled in the center of laminar flow.

Laminar flow has its highest velocities in the center of the vessel

43
Q

Which of the following is false about color Doppler imaging?

  • It is prone to aliasing
  • It obtains mean velocity information
  • It uses autocorrelation as its signal processing technique
  • It can measure peak systolic and end diastolic velocities
A

FALSE - It can measure peak systolic and end diastolic velocities

Color Doppler imaging cannot measure PSV or EDV, only mean velocities

44
Q

Which of the following is a property of power Doppler?

  • Able to obtain velocity information and direction of flow
  • Signal is obtained by detecting amplitude of shift
  • It is prone to aliasing
  • Limited by perpendicular angle of incidence
A

Power Doppler is obtained by measuring the amplitude of the Doppler shift.

45
Q

Assuming flow is constant, what happens in a region of blood vessel narrowing?

  • There is a signficant pressure increase
  • There is an increase in the velocity along with a corresponding increase in pressure
  • There is an increase in the velocity along with a corresponding decrease in pressure
  • Velocity and pressure are unchanged
A

Considering Bernoulli, in a region of a blood vessel narrowing the velocity of the blood will increase, and the pressure will decrease

46
Q

Which of the following is true about the spectral Doppler envelope?

  • It is thin when there are many different velocities
  • It is thin with CW Doppler
  • It is thickened in the center of a laminar flow vessel
  • It is thickened in the presence of turbulence
A

The spectral Doppler envelope is thickened in the presence of turbulence

47
Q

What is the term for the pressure difference between the inside of a vein and the tissue outside?

  • Hydrostatic pressure
  • Autocorrelation
  • Transmural pressure
  • Kinetic energy
A

Transmural pressure is the pressure between the inside of a vein and the tissue outside.

48
Q

A proximal stenosis will look like what on the spectral waveform?

  • Reversal of flow in diastole
  • Delay in the systolic upstroke
  • Triphasic waveform
  • Aliasing
A

A proximal stenosis will look like a delay in the systolic upstroke on the spectral waveform.

49
Q

The end diastolic component is missing on a spectral waveform. Which of the following should be adjusted to fix this?

  • Gain
  • Scale
  • Wall filter
  • Frequency
A

End diastolic component is missing on a spectral waveform, adjusting the wall filter eliminates the low frequency shift component of the spectral waveform

50
Q

In the exercising patient, the distal arterioles are dilated. What type of flow pattern would most likely be demonstrated on spectral Doppler within the proximal vessels?

  • Monophasic
  • Biphasic
  • Triphasic
  • Venous
A

Monophasic flow is seen proximal to a low resistance bed

Monophasic because they are dilated and want to be fed.

Ultrasound Physics (2 decks)

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