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Ultrasound Physics Review > Doppler > Flashcards

Doppler Flashcards

1
Q

The Doppler effect is observed as a change in _____ and has units of _____.

a. amplitude, watts
b. power, watts
c. frequency, per second
d. wavelength, millimeters

A

c. frequency, per second

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2
Q

In clinical imaging, which reflectors produce most relevant Doppler shifts?

a. blood vessels
b. blood plasma
c. platelets
d. red blood cells

A

d. red blood cells

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3
Q

If red blood cells are traveling toward a transducer, the frequency emitted by the transducer is ____ the frequency reflected from the red blood cells.

a. greater than
b. equal to
c. less than

A

c. less than

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4
Q

In standard Doppler, what is true about the reflected frequency produced by blood cells traveling away from the transducer?

a. it is in the audible range
b. it is ultrasonic
c. it exceeds the transmitted frequency
d. it equals the transmitted frequency

A

b. it is ultrasonic

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5
Q

What is the range of Doppler shifts commonly measured in clinical exams?

a. -10 kHz to 1 MHz
b. -0.5 MHz to 0.5 MHz
c. -0.02 MHz to 0.02 MHz
d. none of the above

A

c. -0.02 MHz to 0.02 MHz

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6
Q

When red blood cells move away from a transducer, the frequency of the wave reflected from the red cells is _____ the frequency emitted by the transducer.

a. greater than
b. less than
c. equal to

A

b. less than

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7
Q

What information does the Doppler shift furnish concerning the blood cells that produce it?

a. frequency
b. speed
c. velocity
d. density

A

c. velocity

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8
Q

Blood moving at a velocity of 2 m/s creates a Doppler frequency of 3,000 Hz. What will the Doppler shift be if the velocity increased to 4 m/s?

a. 3,000 Hz
b. 2 Hz
c. 1,500 Hz
d. 6,000 Hz

A

d. 6,000 Hz

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9
Q

Two ultrasound transducers are used to perform Doppler exams on the same patient. The exams are identical except that the transducer frequencies are 5 and 2.5 MHz. Which exam will measure the highest velocities?

a. the 2.5 MHz exam
b. the 5 MHz exam
c. neither
d. cannot be determined

A

c. neither

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10
Q

Two ultrasound transducers are used to perform Doppler exams on the same patient. The exams are identical except that the transducer frequencies are 5 and 2.5 MHz. Which exam will measure that highest Doppler shift?

a. the 2.5 MHz exam
b. the 5 MHz exam
c. neither
d. cannot be determined

A

b. the 5 MHz exam

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11
Q

When using a 4 MHz transducer, a Doppler shift of 3,000 Hz is recorded. What will the Doppler shift be when a 2 MHz transducer is used?

a. 3,000 Hz
b. 2 Hz
c. 1,500 Hz
d. 6,000 Hz

A

c. 1,500 Hz

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12
Q

Doppler does not always provide a called estimate of the speed of blood cells because the shift is related to the _____ of the angle between the direction of the beam and the direction of blood flow.

a. sine
b. tangent
c. cosine
d. cotangent

A

c. cosine

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13
Q

Two otherwise identical Doppler studies are performed, except that the angle between flow and the sound beam is 0 degrees in the first study and 60 degrees in the second. The velocity measured in the first study is 2 m/s. What is will the velocity be measured in the second study?

a. 2 m/s
b. 4 m/s
c. 1 m/s
d. cannot be determined

A

c. 1 m/s

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14
Q

What is true of the Doppler shift when the sound beam is normally incident to the velocity of the red blood cells?

a. it is at maximum
b. it is half of maximum
c. it is absent
d. it is at minimum

A

c. it is absent

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15
Q

A maximum Doppler shift is obtained when the angle between the direction of blood flow and the direction of the sound beam is _____.

a. 10 degrees
b. 90 degrees
c. 180 degrees
d. 270 degrees

A

c. 180 degrees

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16
Q

True or False?

The appearance of negative velocities on the spectral display of a continuous wave Doppler exam always indicates that red blood cells are moving away from the transducer.

A

True

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17
Q

With regard to CW Doppler, True or False?

A minimum of two distinct piezoelectric crystals are in the transducers.

A

True

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18
Q

With regard to CW Doppler, True or False?

Problems with aliasing significantly limit its clinical utility.

A

False

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19
Q

With regard to CW Doppler, True or False?

Frequencies measured at the transducer are produced from many different locations along the ultrasonic beam.

A

True

20
Q

With regard to CW Doppler, True or False?

The duty factor of the continuous wave is 100%.

A

True

21
Q

All of the following are related to dedicated continuous wave Doppler transducers except:

a. wide bandwidth
b. high quality factor
c. higher sensitivity
d. range ambiguity

A

a. wide bandwidth

22
Q

A duplex ultrasound system displays _____ information.

a. M-mode, two-dimensional image, and A-mode
b. A-mode and B-mode
c. two-dimensional image and Doppler
d. two-dimensional image and M-mode

A

c. two-dimensional image and Doppler

23
Q

All of the following are associated with a CW Doppler transducer except:

a. narrow bandwidth
b. increased sensitivity
c. backing material
d. high Q-factor

A

c. backing material

24
Q

The information that is processed by a standard duplex ultrasound system includes all of the following except:

a. attenuation
b. amplitude
c. frequency
d. time of arrival

A

a. attenuation

25
Q

True or False?

The appearance of negative velocities in a pulsed Doppler display always indicates that red blood cells are moving away from the transducer.

A

False

26
Q

With pulsed Doppler, what term is used to describe a very positive Doppler shift that is displayed as a negative waveform?

a. attenuation
b. filtering
c. demodulation
d. aliasing

A

d. aliasing

27
Q

The highest Doppler frequency without the appearance of aliasing is called the _____ and is equal to _____.

a. aliasing limit, half of the emitted frequency
b. pulse repetition frequency, the pulse repetition frequency
c. Nyquist limit, half of the emitted frequency
d. Nyquist limit, half of the emitted PRF

A

d. Nyquist limit, half of the emitted PRF

28
Q

True or False?

In a pulsed Doppler exam, the use of a higher transducer frequency increases the likelihood that aliasing will appear.

A

True

29
Q

True or False?

The higher the pulse repetition frequency of a Doppler exam, the more likely aliasing is to occur.

A

False

30
Q

A system has three transducers with frequencies of 7.5 MHz, 5 MHz, and 3.25 MHz. Aliasing appears while using the 5.0 MHz transducer during a pulsed Doppler exam. What should the sonographer do?

a. use the 3.25 MHz transducer
b. used the 7.5 MHz transducer
c. nothing; the other transducers do not provide solutions to the problem

A

a. use the 3.25 MHz transducer

31
Q

The frequency of a pulsed Doppler wave is 6 MHz, and the PRF is 5 kHz. What is the maximum Doppler shift that can be recorded without aliasing?

a. 6 MHz
b. 5 kHz
c. 3 MHz
d. 2.5 kHz

A

d. 2.5 kHz

32
Q

During a pulsed Doppler exam, aliasing is observed. All of the following may eliminate aliasing except:

a. selection of another imaging view with a shallower sample volume
b. selection of another transducer with a lower frequencies
c. selection of another imaging view that provides a greater pulse repetition period
d. use of continuous wave system

A

c. selection of another imaging view that provides a greater pulse repetition period

33
Q

True or False?

TGC cannot be used with continuous wave Doppler.

A

True

34
Q

Which of the following determines the gray scale in a Doppler spectrum?

a. number of reflectors
b. velocity
c. frequency shift
d. laminar flow

A

a. number of reflectors

35
Q

Which choice relates to the presence of gray shades in a Doppler spectrum?

a. velocity
b. frequency shift
c. amplitude of the echo
d. laminar flow

A

c. amplitude of the echo

36
Q

True or False?

Color flow Doppler exams tend to have lower temporal resolution than traditional two-dimensional, real-time imaging.

A

True

37
Q

True or False?

Color flow Doppler imaging incorporates pulsed Doppler principles and provides range resolution.

A

True

38
Q

True or False?

Color flow Doppler relies on pulsed Doppler principles and is immune to aliasing artifact.

A

False

39
Q

True or False?

Color flow Doppler systems display anatomical data in gray scale while simultaneously displaying flow information in color.

A

True

40
Q

True or False?

On a color Doppler image, red always represents flow toward the transducer, whereas blue indicates flow away from the transducer.

A

False

41
Q

True or False?

Absence of color on a color Doppler image always indicates a region of no blood flow.

A

False

42
Q

The two most common color maps used in color flow imaging are:

a. variance and direct
b. variance and velocity
c. turbulence and variance
d. power and velocity

A

b. variance and velocity

43
Q

True or False?

Variance mode color maps may be identified by side-by-side changes in the color bar, whereas velocity mode color maps only change color vertically.

A

True

44
Q

True or False?

Velocity mode color Doppler and variance mode color Doppler will produce identical images when blood flow patterns are laminar.

A

True

45
Q

True or False?

Velocity mode color Doppler and variance mode color Doppler will produce identical images when blood flow patterns are turbulent.

A

False

Ultrasound Physics Review (30 decks)

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