Doppler

Question 1

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

Answer 1

c. frequency, per second

Question 2

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

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

Answer 2

d. red blood cells

Question 3

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

Answer 3

c. less than

Question 4

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

Answer 4

b. it is ultrasonic

Question 5

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

Answer 5

c. -0.02 MHz to 0.02 MHz

Question 6

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

Answer 6

b. less than

Question 7

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

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

Answer 7

c. velocity

Question 8

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

Answer 8

d. 6,000 Hz

Question 9

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

Answer 9

c. neither

Question 10

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

Answer 10

b. the 5 MHz exam

Question 11

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

Answer 11

c. 1,500 Hz

Question 12

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

Answer 12

c. cosine

Question 13

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

Answer 13

c. 1 m/s

Question 14

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

Answer 14

c. it is absent

Question 15

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

Answer 15

c. 180 degrees

Question 16

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.

Answer 16

True

Question 17

With regard to CW Doppler, True or False?

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

Answer 17

True

Question 18

With regard to CW Doppler, True or False?

Problems with aliasing significantly limit its clinical utility.

Answer 18

False

Question 19

With regard to CW Doppler, True or False?

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

Answer 19

True

Question 20

With regard to CW Doppler, True or False?

The duty factor of the continuous wave is 100%.

Answer 20

True

Question 21

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

Answer 21

a. wide bandwidth

Question 22

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

Answer 22

c. two-dimensional image and Doppler

Question 23

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

Answer 23

c. backing material

Question 24

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

Answer 24

a. attenuation

Question 25

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.

Answer 25

False

Question 26

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

Answer 26

d. aliasing

Question 27

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

Answer 27

d. Nyquist limit, half of the emitted PRF

Question 28

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

Answer 28

True

Question 29

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

Answer 29

False

Question 30

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

Answer 30

a. use the 3.25 MHz transducer

Question 31

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

Answer 31

d. 2.5 kHz

Question 32

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

Answer 32

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

Question 33

True or False? TGC cannot be used with continuous wave Doppler.

Answer 33

True

Question 34

Which of the following determines the gray scale in a Doppler spectrum? a. number of reflectors b. velocity c. frequency shift d. laminar flow

Answer 34

a. number of reflectors

Question 35

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

Answer 35

c. amplitude of the echo

Question 36

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

Answer 36

True

Question 37

True or False? Color flow Doppler imaging incorporates pulsed Doppler principles and provides range resolution.

Answer 37

True

Question 38

True or False? Color flow Doppler relies on pulsed Doppler principles and is immune to aliasing artifact.

Answer 38

False

Question 39

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

Answer 39

True

Question 40

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

Answer 40

False

Question 41

True or False? Absence of color on a color Doppler image always indicates a region of no blood flow.

Answer 41

False

Question 42

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

Answer 42

b. variance and velocity

Question 43

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.

Answer 43

True

Question 44

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

Answer 44

True

Question 45

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

Answer 45

False